Bright iridescent patches are honest signals!

Purple Sapphire (Heliophorus epicles) male showing iridescent blue patches on upper wing surfaces

Males butterflies in the family Lycaenidae, the so-called Blues, typically have brightly coloured, iridescent colours on the upper (dorsal) surfaces of their wings. Vivid blue iridescence such as this on the Purple Sapphire (Heliophorus epicles) shown here, is usually to do with courtship and mate recognition.

The brightly coloured, iridescent males rely on so-called, structural colouration (described below), which is used both in male-to-male interactions (competition), and in attracting females, via flickering or flashing their bright wings. The females are often dark brown and mostly lacking in these bright structural colours. They may – like female Purple Sapphires – have bright pigmentary colours (orange flashes in this case), but these are probably not secondary sexual characters, i.e. used in courtship and mating. I don’t have a picture of the female, but there are many examples on this website (1).

Purple Sapphire (Heliophorus epicles) side view showing brightly coloured, but mostly, non-iridescent under wings

A variety of different types of microscopic ‘nanostructures’ – extremely small regular structures – have been found to generate blue colours in lycaenid butterflies. Many have so-called multilayers – alternating layers of chitin and air – within the individual scales (2, 3).

Purple Sapphire (Heliophorus epicles) male showing iridescent blue patches on upper wing surfaces and antennae

Butterfly wings are covered on both sides by rows of tiny overlapping scales, a bit like very thin, flat roof tiles or shingles. Scales can vary markedly in size and shape across the wing of a butterfly, but depending on the species, there are about 200–600 scales per square millimetre of wing. The scales are very delicate, typically one or two microns (i.e. one thousand times smaller than a millimetre) in thickness, and are denuded by wear and tear as butterflies age.

It has been suggested that the fact that scales detach so easily is an adaptation to allow butterflies (and moths) to escape from spider’s webs. (4). Scales that are attached to the sticky threads of the spider’s web can be sacrificed to allow the butterfly to regain its freedom.  

Each scale consists of two layers held together by a series of tiny pillars. The lower layer of the scale is flat and smooth between 100 to 200 nanometres (one nanometre is a billionth of a metre) in thickness – whilst the upper layer consists of a series of longitudinal ridges or striae – about one or two microns apart – and transverse crossribs which create a three dimensional lattice, or honeycomb structure with windows into the interior of the scale (5). It is the elaborate 3-D nanostructures so-called perforated multilayers – between the lamellae that cause the structural colours and phenomena like iridescence (3).

The reflected iridescence produced by light scattering from the dorsal wing scales of many lycaenids is highly directional, i.e. it is only observable from a narrow angular window. That is why the blue colour is not visible in some photographs (see below), although the scales can also be denuded.

Purple Sapphire (Heliophorus epicles) male showing no iridescent blue patches, probably due to the angle of the wing

The iridescence produced by male wings of butterflies such Heliophorus epicles, and countless other species, appears to be what is called a secondary sexual character. In other words, female butterflies evaluate these colours when choosing which males to mate with. They have also been called ‘colour badges’ and are thought to be honest signals, or reliable information if you will, of the condition of the males (6).  So the theory is that males with a good pedigree (i.e. genes) and a good upbringing (i.e. favourable environmental conditions) will be bright and showy (!), and females will choose them on the basis that they are more likely to be vigorous and fertile.

Presumably because they are ‘costly’ to produce or difficult to generate, and the scales producing the effect are lost, or worn down as the male butterflies age, then structural colours appear to provide a good indication of male quality and vigour in some species. However, even old and worn males – like the individual shown in the following photograph – still have some iridescent scales with which to attract the ladies!

Purple Sapphire (Heliophorus epicles) male showing worn iridescent blue patches

Although there is, as far as I know, no definitive evidence that female butterflies choose between males on the basis of the quality of the intensity, hue or saturation of their reflective colours, the available evidence supports the idea that brilliant male structural colours evolved as a result of sexual selection (7). It seems that sexual selection in butterflies has homed in on the brightness of these structural colours in the same way that it has in terms of the brightness and ornamentation of the peacock’s tail feathers.

I have focused on the blue patches on the upper sides of the males wings in this blog. The bright yellow and red colours on the undersides also clearly have some function, but it is probably not to do with mating (I’m only guessing!) as the males and females look relatively similar on their undersides. Who knows what really goes on in the minds of these butterflies!

Purple Sapphire (Heliophorus epicles) side view showing brightly coloured, but mostly, non-iridescent under wings

All of these photographs were taken in Thailand.

  1. Mazumder, S. 2017. Heliophorus epicles Godart, 1823 – Purple Sapphire. Kunte, K., P. Roy, S. Kalesh and U. Kodandaramaiah (eds.). Butterflies of India, v. 2.24. Indian Foundation for Butterflies.
    http://www.ifoundbutterflies.org/sp/728/Heliophorus-epicles
  2. Vértesy, Z., Bálint, Z., Kertész, K., Vigneron, J. P., Lousse, V., & Biró, L. P. (2006). Wing scale microstructures and nanostructures in butterflies − natural photonic crystals.Journal of microscopy,224(1), 108-110. 
  3. Wilts, B. D., Leertouwer, H. L., & Stavenga, D. G. (2008). Imaging scatterometry and microspectrophotometry of lycaenid butterfly wing scales with perforated multilayers.Journal of The Royal Society Interface, rsif-2008. 
  4. Eisner, T., Alsop, R., & Ettershank, G. (1964). Adhesiveness of spider silk.Science,146(3647), 1058-1061.
  5. Stavenga, D. G. (2014). Thin film and multilayer optics cause structural colors of many insects and birds.Materials Today: Proceedings,1, 109-121.
  6. Kemp, D. J. (2006). Heightened phenotypic variation and age-based fading of ultraviolet butterfly wing coloration. Evolutionary Ecology Research, 8(3), 515-527.
  7. Kemp, D. J., Vukusic, P., & Rutowski, R. L. (2006). Stress‐mediated covariance between nano‐structural architecture and ultraviolet butterfly coloration. Functional Ecology, 20(2), 282-289.

 

 

 

 

Red Admirals – European migrants

Red Admiral (Vanessa atlanata) dorsal side. Galicia, Spain. 11 June.

Migrant Red Admirals Vanessa atalanta (L.), usually arrive in the UK during May and June each year. Like the closely related butterfly, The Painted Lady, Vanessa cardui (L.), these migrations of Red admirals originate from countries around the Mediterranean – possibly as far south as the North African coast. (2) The butterflies fly north on southerly winds to feed on new growth as it becomes available in the Spring (1).

The Painted Lady, Vanessa cardui (L.) on Aesculus californica. Barcelona, Spain. 6th June.

Most European Red Admirals  migrate north in the Spring and – after producing a new generation – migrate south again in the Autumn. (3)  This seasonal movement appears to occur right across Europe and western Asia, although this still needs confirmation from many regions, with waves of migrants moving north, for example up into Finland, northern Norway and northern Russia. (4, 5, 9, 10).

Red Admiral (Vanessa atlanata) feeding on thistle. Galicia, Spain, 11 June.

Red Admirals arriving in the UK, mate and lay their eggs mainly on stinging nettles (Urtica diocia); a new generation emerges sometime over the period, August to October.  A small number of Red Admirals remain to overwinter in the British Isles (mainly in southern England) – although numbers appear to be increasing with climate change – whilst the majority elect to migrate. (3) How does this choice to migrate or not work in practice? “Should I stay or should I go now”?! (6). Perhaps a small proportion of the population are genetically programmed not to migrate?

The Red Admiral (Vanessa atalanta) on bell heather. Galicia, Spain, 28th August.

Of those individuals that remain in the UK, it is not thought that they hibernate in a physiological sense, although many sites state that they do hibernate, I think it is true to say that they merely remain dormant, since they can become active on sunny days throughout the winter. (5)  Some of these remaining butterflies must mate in the autumn, as there are records of V. atalanta larvae developing slowly over winter. In other words, a second generation gradually develops over the period from autumn until the following spring. This is exactly what happens when the migrants arrive back in Spain in October and early November as well; ‘larval development occurs throughout the winter until a first annual generation of adults appears in early spring’ (Stefanescu, 2001). (3)

The Red Admiral (Vanessa atalanta) on bell heather. Galicia, Spain, 28th August.

The small proportion of the UK population which do not migrate south are in effect opportunists, which presumably do well in mild winters but suffer heavy mortality in cold ones. The home-grown adults appear in early spring in the UK, well before the next wave of migrants arrive from southern climes, but the overall contribution of these overwintering individuals is thought to be minimal; populations in northern Europe were considered to be entirely dependent on immigration which determines abundance (8). This situation may however, be changing as the climate warms.

The Red Admiral (Vanessa atalanta) on bell heather. Galicia, Spain, 28th August. Wings held in typical 3/4’s open position (See Link 11).

Red Admirals flying southwards in September, in Finland, were found to migrate on sunny days when cool northern winds were blowing (13). Red Admirals take about 5 weeks to fly the 3,000 km from Northern Europe down to the countries surrounding the Mediterranean (1). Circumstantial evidence from meteorological radar observations suggests that they migrate at high altitudes (up to 2,000m or more), where temperatures may be as low as 2-3 deg C! Once they arrive in the south again, in places such as the Catalonia lowlands in north-east Spain – in October and early November, they start breeding a new generation. (2)

The Red Admiral (Vanessa atalanta) on bell heather. Galicia, Spain, 28 August.

Not all Red Admirals migrate over long distances. Studies in Spain by Stefanescu (2001) have shown that some individuals fly much shorter distances towards nearby locations of a high altitude. The butterflies shown here (e.g. above and below) feeding on bell heather were photographed in late August at one such location, near the peak of a hill in Galicia, Spain.

The Red Admiral (Vanessa atalanta) on bell heather. Galicia, Spain, 28 August.

Citizen science projects, such as the one on Red Admiral migration run by the Insect Migration & Ecology Research Group, at the University of Bern, Switzerland (13), offer enormous potential for gathering information on insect migration. People all over Europe can record sightings on a plethora of citizen science portals – some of which are configured as easy to use Apps – allowing researchers to build up unprecedented data bases of records in time and space. It will be fascinating to see what they can come up with in terms of new findings.

  1. Stefanescu, C., Alarcón, M., & Àvila, A. (2007). Migration of the painted lady butterfly, Vanessa cardui, to north‐eastern Spain is aided by African wind currents. Journal of Animal Ecology, 76(5), 888-898.
  2. Brattström, O., Bensch, S., Wassenaar, L. I., Hobson, K. A., & Åkesson, S. (2010). Understanding the migration ecology of European red admirals Vanessa atalanta using stable hydrogen isotopes. Ecography, 33(4), 720-729.
  3. Stefanescu, C. (2001). The nature of migration in the red admiral butterfly Vanessa atalanta: evidence from the population ecology in its southern range. Ecological Entomology, 26(5), 525-536.
  4. Fox, R. & Dennis, R. L. (2010). Winter survival of Vanessa atalanta (Linnaeus, 1758)(Lepidoptera: Nymphalidae): a new resident butterfly for Britain and Ireland?. Entomologist”s Gazette, 61(2), 94.
  5. Bolotov, I. N., Bochneva, I. A., Podbolotskaya, M. V., Gofarov, M. Y., & Spitsyn, V. M. (2015). Butterflies (Lepidoptera: Papilionoidea and Hesperioidea) from meadows of Vinogradovsky District, Arkhangelsk Region, northern European Russia, with notes on recent intense expansion of the southern species to the north. Check List, 11(5), 1727.
  6. https://www.youtube.com/watch?v=BN1WwnEDWAM (The Clash video).
  7. http://nurturing-nature.co.uk/wildlife-garden-videos/red-admiral-butterflies-do-they-hibernate-in-britain/
  8. Pollard, E., & Greatorex-Davies, J. N. (1998). Increased abundance of the red admiral butterfly Vanessa atalanta in Britain: the roles of immigration, overwintering and breeding within the country. Ecology Letters, 1(2), 77-81.
  9. Brattström, O. (2007). Ecology of red admiral migration. Department of Animal Ecology, Lund University.
  10. Brattström, O., Åkesson, S., & Bensch, S. (2010). AFLP reveals cryptic population structure in migratory European red admirals (Vanessa atalanta). Ecological Entomology, 35(2), 248-252.
  11. Peter B. Hardy. The Butterflies of Greater Manchester. http://www.oocities.org/pgll@btopenworld.com/bgm/bgm.htm
  12. Mikkola, K. (2003). Red admirals Vanessa atalanta (Lepidoptera: Nymphalidae) select northern winds on southward migration. Entomol. Fenn., 14(1), 15-24.
  13. https://insectmigration.wordpress.com/red-admiral-migration/

Tigers mating

Danaus chrysippus bataviana male and female in copulation
Danaus chrysippus bataviana male and female in copulation

The Plain Tiger, Danaus chrysippus (Linnaeus, 1758), is a butterfly with an enormous distribution – from West Africa to New Zealand (1, 2). There are a large number of different forms or subspecies comprising what is called a ‘species complex’. This is a name given to a group of insects by taxonomists when they don’t really know, or disagree, as to whether the different forms are genuine species, or subspecies, or semi-species, or just a confusing plethora of hybridizing populations evolving before our eyes!

Danaus chrysippus bataviana male nectaring
Danaus chrysippus bataviana male nectaring

Evidence of the variation in this ‘species complex’ is reflected in the variety of common names for this butterfly: Plain Tiger, Common Tiger, African Monarch, Lesser Wanderer, African Queen and so on. There is an even longer list of synonyms, that is to say, alternative scientific names that have been used, superseded or revised down the centuries.

Danaus chrysippus bataviana male showing ups right wing pattern clearly
Danaus chrysippus bataviana male showing ups right wing pattern clearly

To get round the problem of trying to come up with a name for an entity which includes a number of different forms or subspecies, biologists use the term sensu lato, meaning ‘in the broad sense’. Hence Danaus chrysippus sensu lato (s.l.) is the term used to describe all of the different forms, subspecies, or what have you, of this polytypic butterfly, which occur throughout most of the Afrotropical, Oriental and Australian Regions. There are of course definitive biological features which distinguish the butterflies within this D. chrysippus complex, i.e. from all other Danaus species. These include the presence of certain white scales and black spots on the hind-wings (1).

Danaus chrysippus bataviana male nectaring
Danaus chrysippus bataviana male nectaring

The Oriental form of the Plain Tiger, Danaus chrysippus chrysippus Linnaeus, 1758 – has perhaps the widest distribution, from Morocco all the way across the Old World to southern Japan. The life history of this butterfly has been comprehensively described and illustrated on the excellent, Butterflies of Singapore, website (3). There are also a large number of photographs of this subspecies on the Butterflies of India website (4).

Danaus chrysippus bataviana male nectaring
Danaus chrysippus bataviana male nectaring

The subspecies shown here, Danaus chrysippus bataviana, has a much more limited distribution and occurs only on Java, Sulawesi (part) and the Lesser Sunda Islands, which include Bali, all in Indonesia. These photographs were taken on Bali. The upper hind wings of this subspecies appear to be darker (described as brown by one authority) than those of D. c. chrysippus (5). There are also reports of this subspecies occurring in Malaysia, together with D. c. chrysippus, in isolated but sometimes dense colonies (6), which makes me wonder just how geographically distinct these different subspecies are. Indeed, Smith (2014) states that: ‘D. c. bataviana and D. c. chrysippus are distinct subspecies separated by a narrow, dynamic hybrid zone which has, and may still be, on the move’. It would be interesting to know whether anyone has studied this butterfly across these regions?

Danaus chrysippus bataviana male showing upper (dorsal) side on wings
Danaus chrysippus bataviana male showing upper (dorsal) side on wings

It is fairly easy to tell the sexes apart in these species. The males have a large black spot on the hind-wings which the females lack. On the dorsal or upper-side of the hind-wing, this feature bulges outwards (see photo below, of Plain tiger butterfly in profile) and is called an alar pocket (7).

Danaus chrysippus bataviana male in profile showing alar pockets bulging on upper-side of hind-wing (white circle)
Danaus chrysippus bataviana male in profile showing alar pockets bulging on upper-side of hind-wing (white circle)

On the ventral, or underside, of the hind-wing, the so-called, subtornal brand is also visible as a black spot, but unlike on the top (dorsal) side, it has a prominent white spot within it. This lies alongside the third wing vein from the left (or central) side of the hind-wing, looking down. This white spot is the surest way to identify a male. The female has no such black mark with a white centre (see directly below).

Danaus chrysippus bataviana female on Rinca Is (Komodo National Park, Indonesia).
Danaus chrysippus bataviana female on Rinca Is (Komodo National Park, Indonesia).
Danaus chrysippus bataviana male
Danaus chrysippus bataviana male

Male milkweed butterflies (subfamily, Danainae, in the family Nymphalidae) have a pair of specialised scent-producing organs, called hair-pencils, at the tip of their abdomens. During courtship the hair pencils are everted to form two round bundles of hairs that look rather like toilet brushes! (See image on website below, #9). The function of these organs is to brush the females antennae and transfer a fine dust of pheromone particles. If the female is responsive to this advance, she flies down to the ground, where the male joins her.

Danaus chrysippus bataviana male in flight
Danaus chrysippus bataviana male in flight

It is known that the hair pencils of the male are first inserted into their alar pockets in order to make contact with the glands in this organ which produce a pheromone. Presumably they do this before everting the bristles? Males are unable to excite the females into copulation without first extracting the substance emanating from these alar glands. Armed with the dust-like pheromone particles he is able to dance in front of the female and transfer the magic potion!

Danaus chrysippus bataviana male nectaring and showing abdomen
Danaus chrysippus bataviana male nectaring and showing abdomen

There is however, no guarantee that the female will be receptive. Females might reject males for a number of reasons; he just might not look right (being a different subspecies perhaps); he might be too small (she may be seeking a large spermatophore produced by a large male); he might not smell right (the sex pheromones and volatile cuticular hydrocarbons); or she may have already mated (1). Bad luck! She indicates her refusal by bending her abdomen in a certain way and flapping her wings. It would be nice to be able to photograph these behaviours.

But if the courtship sequence is successful, the pair will remain locked together in copula for a good number of hours. Smith (2014) recorded an average time of 3.5 hours in copula for captive D. chrysippus (5), with some couples remaining together for up to 5 hours. The pair fly off together in what is called a post-nuptial flight. According to Smith (2014), the male is usually larger than the female – although other websites, including Wikipedia, state that the male plain tiger is smaller than the female – and he easily carries her off to a site where they can remain undisturbed for the remainder of the time they are locked together. The male aedeagus (penis) fits into a pocket beneath the ovipositor of the female and the sex organs are locked tightly together whilst the spermatophore is transferred. The female remains passive with limbs folded (see photo below). Smith (2014) reports a sighting of large female carrying a smaller male, so as is often the case in biology, there are no hard and fast rules about who is on top! It is possible that there is variation between subspecies with regard to size and role in terms of who is carrying whom?!

Danaus chrysippus bataviana male and female in copulation
Danaus chrysippus bataviana male and female in copulation

Much of this blog was based on information contained in the excellent volume on African Queens by David Smith, FRES, FLS. The main focus of the book is Danaus chrysippus (L.) sensu strico, which he considers is a ‘superspecies’ – a ‘complex of actively evolving populations’ comprising ‘incipient (imperfectly formed but actively evolving) semi- and subspecies’, rather than a single polymorphic species. Recent research has however, suggested that the D. chrysippus species complex should be separated into two separate species: a polytypic – meaning containing more that two subspecies – D. chrysippus, and monotypic D. petilia.  So not a very big change, as most of the subspecies remain. These two new species occur in distinct but contiguous areas, separated by Lydekker’s Line, separating Australian and Oriental faunas (see map in reference 1). Danaus petilia, known as the Lesser Wanderer, is a migratory species, found in Australia (8).

Whether there are one, two or three species, or seven or eight subspecies – or semi-species – need not concern us! Such matters are best left to taxonomists to sort out! As far as I am concerned it is a beautiful butterfly and I look forward to seeing and photographing some more of the different forms of this butterfly, which represents evolution in action.

Whilst writing this blog, I came across a similar account of mating in Plain tigers by another blogger: Krishna Mohan (10).

All of these images, apart from the one of the female from Komodo NP, were taken in Bali Barat NP, Bali, Indonesia, in October 2016.

  1. Braby, M. F., Farias Quipildor, G. E., Vane-Wright, R. I., & Lohman, D. J. (2015). Morphological and molecular evidence supports recognition of Danaus petilia (Stoll, 1790)(Lepidoptera: Nymphalidae) as a species distinct from D. chrysippus (Linnaeus, 1758). Systematics and Biodiversity, 13(4), 386-402.
  2. Lushai, G., Zalucki, M. P., Smith, D. A., Goulson, D., & Daniels, G. (2005). The lesser wanderer butterfly, Danaus petilia (Stoll 1790) stat. rev.(Lepidoptera: Danainae), reinstated as a species. Australian Journal of Entomology, 44(1), 6-14.
  3. http://butterflycircle.blogspot.co.uk/2010/11/life-history-of-plain-tiger.html
  4. Lovalekar, R., K. Saji, T. Bhagwat & Manoj P. 2017. Danaus chrysippus Linnaeus, 1758 – Plain Tiger. Kunte, K., P. Roy, S. Kalesh and U. Kodandaramaiah (eds.). Butterflies of India, v. 2.24. Indian Foundation for Butterflies.
    http://www.ifoundbutterflies.org/sp/744/Danaus-chrysippus
  5. Smith, D. A. (2014). African queens and their kin: a Darwinian odyssey. Taunton, UK: Brambleby Books.
  6. Smith, D. A., Gordon, I. J., & Allen, J. A. (2010). Reinforcement in hybrids among once isolated semispecies of Danaus chrysippus (L.) and evidence for sex chromosome evolution. Ecological Entomology, 35(s1), 77-89.
  7. Urquhart, F. A. 1976. Alar pocket of the male Monarch butterfly (Danaus p. plexippus) (Danaidae: Lepidoptera). Canadian Entomologist 108:777-782.
  8. http://www.brisbaneinsects.com/brisbane_nymphs/LesserWanderer.htm
  9. http://www.flickriver.com/photos/lionyang/2228664296/
  10. http://drkrishi.com/mating-trouble/

Bluff and deception in Blues

Longbanded Silverline (Spindasis lohita)
Longbanded Silverline (Spindasis lohita)

The Longbanded Silverline (Spindasis lohita), Family Lycaenidae, is a beautiful insect with a remarkable structure – a tail, or ‘false head’ – at the end of its hind wing. There is a bright orange tornal patch – the tornus is the posterior corner of the butterfly wing – on both sides of the wing. There is also a black eye-spot and two pairs of white-tipped, filament-like black tails, or ‘false antennae’, at the end of the wing. Interestingly, many lycaenids have similar black and orange eye-spots and single or double tails.  For example, the Common Tit (Hypolycaena erylus himavantus) also has white-tipped, double tails similar to this species (1). So presumably it was a feature that evolved at sometime during the history of this family. Black and orange make a very eye-catching colour combination.

It is widely assumed that these structures are a ‘false head’ (or ‘fake head’), which acts to divert predatory attacks, e.g. bird pecks, away from the real head (and body) and towards the back of the butterfly. There is plenty of evidence that butterflies really do get pecked at, or on, these hindmost eye-spots (2). It is surprising therefore, that very little rigorous experimentation has been carried out to thoroughly investigate this phenomenon. In other words, the ‘false head’ hypothesis has not been tested scientifically. That is not to say it is not true, it is just a subject that ‘remains ripe for testing’ according to Professor Martin Stevens (3).

Long-banded Silverline (Spindasis lohita) - close-up of false head
Long-banded Silverline (Spindasis lohita) – close-up of false head

The fact that these butterflies invest so much time and energy into producing these deceptive structures and moving the little tails about like false antennae, is to my mind, quite convincing circumstantial evidence for their utility in avoiding predation, or surviving an attack. It is clear how prominent the ‘false head’ is – and might appear to a bird – when looking down on the butterfly from above (see photo below) like a bird might see it. The real head is partly hidden underneath the wings, but the ‘false head’ is very prominent.

Long-banded Silverline (Spindasis lohita), looking down from above
Long-banded Silverline (Spindasis lohita), looking down from above

The lovely wing colours of this butterfly are a tapestry, to borrow a term used by lepidopterists, of tiny overlapping scales of different colours: red, silver, orange, white and black. The scales can be seen in two excellent close-up photographs of the wings of this butterfly on this webpage (4). Males of this species also have bright, iridescent blue patches on both dorsal fore- and hind-wings. It is possible that these, together with the contrasting orange patches, could also act to startle and deter a predator and give the butterfly time to make its escape.

  1. https://rcannon992.com/2015/01/30/pushmi-pullyu-butterfly/
  2. https://rcannon992.com/2016/01/17/peck-me-here-butterfly-predation/
  3. Stevens, M. (2016). Cheats and Deceits: How Animals and Plants Exploit and Mislead. Oxford University Press.
  4. http://butterflycircle.blogspot.co.uk/2010/09/life-history-of-long-banded-silverline.html

Courting Jezebels

Painted Jezebel (Delias hyparete indica) female inserting proboscis into Bourgainvillea flower
Painted Jezebel (Delias hyparete indica) female inserting proboscis into Bougainvillea flower

I spent some time observing and photographing Painted Jezebel (Delias hyparete indica) butterflies feeding and courting on Bougainvillea flowers in Thailand. These beautiful and very common butterflies are often seen flitting around the tops of trees, coming down to feed on flowering plants later in the day (1, 2). Their ubiquity does not detract from their beauty.

Bourgainvillea flowers
Purple Bougainvillea flowers

The day was cloudy and overcast when I took these photographs and I did not use a flash, as I usually prefer natural lighting if I can get away with it. So some of the photographs of the butterflies in flight, are a bit blurred, but I have included them anyway to illustrate some of the behaviour exhibited by this species.

Painted Jezebels (Delias hyparete) female (darker wings) with male above
Painted Jezebels (Delias hyparete) female (darker wings) with male above

Males and females of his species are quite easy to tell apart as the female has much darker,  heavily black-dusted wings – particularly on the upper (dorsal) wing surface – than the male. These butterflies are very active and fast-moving, but it is possible to observe some of the components of courtship behaviour, if you are prepared to follow them and walk round and round a bougainvillea bush! The males were very interested in females, and one, two or three males often chased after a female and followed her to where she was nectaring (feeding on nectar).

Painted Jezebels (Delias hyparete) female (dark wings) with male flying above
Painted Jezebels (Delias hyparete) female (dark wings) with male flying above

Vision is probably more important in the early stages of butterfly courtship; the male must first recognize the female – easy as the differences are marked in this species – and then court her to see if she is interested (termed ‘receptive’ in biology!).  One researcher has described courtship behaviour by male butterflies: the male “barrages the female with visual, chemical and tactile stimuli by buffeting her with his wings or special scent-producing structures when flying near the female” (Rutowski, 1984). In other words, the males use a combination of touching and pheromone release to try and woo the females.

Painted Jezebels (Delias hyparete) male chasing female
Painted Jezebels (Delias hyparete) male chasing female
Painted Jezebels (Delias hyparete) male chasing female in flight
Painted Jezebels (Delias hyparete) male chasing female in flight

On the day I photographed these butterflies, none of the females appeared to be receptive for some reason – they may have already mated – and I did not observe any reproduction on this occasion.

Painted Jezebels (Delias hyparete) two males chasing female
Painted Jezebels (Delias hyparete) two males chasing female

Female butterflies can almost always avoid the attentions of males, and thereby avoid mating, if they are not receptive (Forsberg & Wiklund, 1989). Indeed, some female butterflies have special ‘mate refusal postures’. It is thought that in all pierid butterflies (including this species), the ‘mate-refusal’ posture is an elevated abdomen together with wings spread out as well (Obara, 1964). All of this happens very quickly, within seconds, but I think I might have caught a female raising her abdomen in the following photograph (below). I am not sure however, as butterflies also sometimes have this raised abdomen during flight.

Painted Jezebels (Delias hyparete) two males chasing female
Painted Jezebels (Delias hyparete) two males chasing female

I don’t know how high the abdomen must be raised or whether it varies from species to species? I suppose the females who are not interested keep raising their abdomens until the male(s) desist and fly off! In contrast, is a lowered, or unelevated, abdomen a ‘come on’ sign in this family?!

Painted Jezebel (Delias hyparete indica) female inserting (or withdrawing?) proboscis
Painted Jezebel (Delias hyparete indica) female inserting (or withdrawing?) proboscis

Another interesting behaviour to capture is nectaring. The butterflies move rapidly between individual flowers on a bush in a seemingly random manner (but it might not be!). The proboscis is carefully, but rapidly inserted into the corolla tube of the flower. The butterfly appears to press it further down into the flower as far as possible, until it’s head is right up against the opening of the corolla tube.

There are tiny yellow anthers within the cream coloured corolla tube (just visible in the following photo) which the butterfly has to negotiate as it inserts its proboscis down towards the base of the corolla, where the nectar lies.

Painted Jezebel (Delias hyparete indica) female with proboscis fully inserted. Flowers showing tiny yellow anthers.
Painted Jezebel (Delias hyparete indica) female with proboscis fully inserted. Flowers showing tiny yellow anthers.

The proboscis is removed and curled up whilst the butterfly is in flight. Similarly, it is uncurled prior to arrival at the flower so it can be inserted immediately. The butterfly on the left in the following photo (below) is starting to unfurl his – it is hard to say whether this is a male of female – proboscis in preparation for landing on a flower.

Painted Jezebels (Delias hyparete) male chasing female (uncurling proboscis)
Painted Jezebels (Delias hyparete) two males (one uncurling proboscis)

The butterflies were moving rapidly between flowers, generally spending less than a few seconds on each flower but occasionally longer. Were these the ones with a good supply of nectar?  There were a great many flowers to choose from; could they – like some bumblebee species can – tell whether a flower had been visited by another butterfly recently? I don’t know. I suspect not. In which case, it was perhaps a matter of trial and error to search for a flower which had a good supply of nectar and had not been visited recently. Scope for a research project here!

There was a definite sequence to the nectaring. The proboscis was inserted but at first retained a curved shape as it was pushed down into the tube of the corolla (see below).

Painted Jezebel (Delias hyparete indica) female inserting proboscis into corolla tube
Painted Jezebel (Delias hyparete indica) female inserting proboscis into corolla tube

The butterfly carried on inserting the proboscis – and presumably searching for nectar – until the head of the butterfly was right up against the top of the corolla (see second photo below).

Painted Jezebel (Delias hyparete indica) male inserting proboscis
Painted Jezebel (Delias hyparete indica) male inserting proboscis
Painted Jezebel (Delias hyparete indica) male proboscis fully inserted
Painted Jezebel (Delias hyparete indica) male proboscis fully inserted

This was as far as it could go. Butterflies usually visit flowers where they can easily reach the nectar (it would be a bit of a waste of time if the flower was too deep or the proboscis too long!). Lepidopteran proboscises vary enormously in length (from 1 to 50 mm) (4, 5) and species have evolved to feed on certain types of flower where the proboscis roughly matches the length of the corolla. But they are adaptable. Flowers and pollinators have evolved together. In the case of Man-bred hybrids such as these, it is just a matter of luck presumably whether butterflies have the right equipment to extract the nectar. These butterflies certainly did!

There is an enormous academic literature on the biology and ecology of butterflies, but there remains a surprising lack of detailed behavioural studies for some species. So there are great opportunities for amateurs to observe and record butterfly behaviour in the field. Concentrating on a common species such as this, it is possible to gain some insights into their lives. I hope that this account has shown that there is much to be learnt about butterflies and with patience and perseverance they secrets can be discovered!

Links and references

  1. Butterfly of the Month – December 2010: Painted Jezebel (Delias hyparete metarete). http://butterflycircle.blogspot.co.uk/2010/12/butterfly-of-month-december-2010.html
  2. Life History of the Painted Jezebel (Delias hyparete metarete). http://butterflycircle.blogspot.co.uk/2013/05/life-history-of-painted-jezebel.html
  3. Rutowski, R. L. (1984). Sexual selection and the evolution of butterfly mating behaviour. J. Res. Lepid, 23, 125-142.
  4. Forsberg, J., & Wiklund, C. (1989). Mating in the afternoon: Time-saving in courtship and remating by females of a polyandrous butterfly Pieris napi L. Behavioral Ecology and Sociobiology, 25(5), 349-356.
  5. Obara, Y. (1964). Mating behaviour of the cabbage white, Pieris rapae crucivora II: the ‘mate-refusal’posture of the female. Zool. Mag, 73, 175-178.
  6. A Close-up view of a Bougainvillea hybrid. http://www.microscopy-uk.org.uk/mag/indexmag.html?http://www.microscopy-uk.org.uk/mag/artdec10/bj-bvillea.html
  7. Monaenkova, D., Lehnert, M. S., Andrukh, T., Beard, C. E., Rubin, B., Tokarev, A., … & Kornev, K. G. (2011). Butterfly proboscis: combining a drinking straw with a nanosponge facilitated diversification of feeding habits.Journal of the Royal Society Interface, rsif20110392.
  8. Bauder, J. A., Lieskonig, N. R., & Krenn, H. W. (2011). The extremely long-tongued Neotropical butterfly Eurybia lycisca (Riodinidae): proboscis morphology and flower handling. Arthropod structure & development, 40(2), 122-127.

Weaver’s Fritillary

weavers-fritillary-boloria-dia-asturias-3
Weaver’s Fritillary (Boloria dia), Asturias, Spain

It is rather ironic that this little butterfly, which was named by a 19th Century British entomologist, does not occur in the UK! Weaver’s fritillary (Boloria dia) occurs throughout mainland Europe, and is found just across the Channel in northern France (see distribution map, below).

weaver's fritillary (Boloria dia) Asturias, Spain
Weaver’s fritillary (Boloria dia) Asturias, Spain. Gallery of distribution maps of European butterflies. http://www.ufz.de/european-butterflies/index.php?en=22481

It is also called the Violet Fritillary, a name which derives from the violet, or lilac, coloration on the undersides of the hind-wings. I rather like the French name: La petite Violette; it is a small fritillary. Nevertheless, the name goes back to a certain Richard Weaver (1790-1860), who claimed to have captured – sometime in the 1820’s –  two specimens in Sutton Park,  which is now a National Nature Reserve located 6 miles north of Birmingham city centre. These and later dubious finds caused a great furore at the time, when butterfly collecting was something of a national obsession, at least among the upper middle classes in England, and particularly country parsons. The historical details of these finds and the reactions they produced are beautifully described in The Aurelian Legacy (British Butterflies and their Collectors) by Michael A. Salmom. (2)

Weaver's fritillary (Boloria dia) Asturias, Spain.
Weaver’s fritillary (Boloria dia) Asturias, Spain.

Another specimen was taken in September 1857 in the Rev. S. Hodson’s Garden, at Cookham Dean, near Maidenhead in Berkshire. It was said to have been ‘knocked down by a village lad with his cap’ and was claimed to be undoubtedly British. Unfortunately, the claim was challenged and discredited. There was it seems, a great deal of credit (and money!) to be had from discovering a species new to Britain, and fraudulent releases and captures were made.

Further finds, occurred near Tunbridge Wells, Kent (c. 1876); near Christchurch, Dorset (1887); Ipswich, East Suffolk (1899); and much more recently on the North Downs, Surrey (1984). The latter was believed to have been a release. The official verdict on all of the Weaver’s Fritillary finds in Britain is that: ‘It is believed that all examples of this species are the result of introductions, either deliberate or accidental.’ (3) Since the species is not known to migrate, I suppose we must leave it there, although if Monarch butterflies can cross the Atlantic, perhaps a little Fritillary could be blown across the Channel? Who knows.

weaver's fritillary (Boloria dia) Asturias, Spain
Weaver’s fritillary (Boloria dia) Asturias, Spain

In case anyone does come across one in Britain (!), a characteristic feature of this butterfly is the rather sharp angle of the hind-wing, as shown in the following photograph. All of these individuals were photographed in Somiedo Nation Park, Asturias, Spain, in late August/early September this year. I think they are all males.

Weaver's fritillary (Boloria dia) Asturias, Spain. Sharp-angled hind-wing highlighted.
Weaver’s fritillary (Boloria dia) Asturias, Spain. Sharp-angled hind-wing highlighted.

Links and References

  1. Gallery of distribution maps of European butterflies.  http://www.ufz.de/european-butterflies/index.php?en=22481
  2. Salmon, M. A., Marren, P., & Harley, B. (2000). The Aurelian legacy: British butterflies and their collectors. Harley Books.
  3. http://www.ukbutterflies.co.uk/species.php?species=dia

Beautiful Cleopatra

Cleopatra (Gonepteryx cleopatra) male
Cleopatra (Gonepteryx cleopatra) male

The Cleopatra is not a butterfly we see in the UK although a few individuals have occasionally appeared in southern England, perhaps as a result of hitch-hiking on a passing ship! (1) It is not markedly different from the Brimstone until the male opens his wings during flight and reveals beautiful orange patches on the yellow fore-wings. These butterflies do not bask with their wings open, so one needs to photograph it in flight to catch the lovely orange discal colours. I always seem to underestimate the necessary shutter speed; the 1/1,600th of a second in the following photograph was too slow! But on the other hand, perhaps the slight blurring suggests movement?! I love the way the butterfly starts to unfurl its proboscis before it arrives at the flower. They demonstrate remarkable dexterity – if that is the right word – in using their proboscis.

Cleopatra butterfly (Gonepteryx cleopatra) male in flight
Cleopatra butterfly (Gonepteryx cleopatra) male in flight

The Cleopatra butterfly is found throughout southern Europe and across all of Spain, from north to south. There are a number of subspecies. These photographs were taken in the village of Pola, in Somiedo National Park, Asturias, Spain. This is a location where minimum temperatures fall to zero (0 deg C) in the winter. The butterflies were however, enjoying the evening sunshine in August of this year, nectaring on these flowers.

cleopatra-gonepteryx-cleopatra-male-4

The uppersides of the male wings, particularly the fore-wings, of this species strongly reflect light in the ultraviolet region of the spectrum. (2)  Unlike us, butterflies can see UV light and males often use it to show off to females or to discourage would be rivals.  The wings of these butterflies also contain pterin pigments – xanthopterin and erythropterin – which create the bright wing colours. There are also cover scales on the wings, which create structural colours by back-scattering the incident light when it hits a series of microscopic ridges – called nanostructures – on the scales. (3) There is an awful lot more to this structural colour story than I have alluded to here, but it certainly makes for a lovely butterfly.

References

  1. http://www.ukbutterflies.co.uk/species.php?species=cleopatra
  2. Wilts, B. D., Pirih, P., & Stavenga, D. G. (2011). Spectral reflectance properties of iridescent pierid butterfly wings. Journal of Comparative Physiology A, 197(6), 693-702.
  3. Wijnen, B., Leertouwer, H. L., & Stavenga, D. G. (2007). Colors and pterin pigmentation of pierid butterfly wings. Journal of insect physiology, 53(12), 1206-1217.

Watch out little butterfly!

A little butterfly skipping from flower to flower in the late afternoon sunshine.

Small tortoiseshell (Aglais urticae L.)
Small tortoiseshell (Aglais urticae L.)

Enjoying little sips of nectar. Seemingly oblivious to the cares of this world.

tortoiseshell-ups
Small tortoiseshell (Aglais urticae L.)

Yet there lurks a trap for this innocent little sprite. A spider has cast its net.

Orb spider with butterfly capture
Orb spider with butterfly capture

Nature is not nice, or sweet. The innocent get consumed. Do the fittest always survive? Or does blind chance decree who gets caught and who remains free to fly another day?

Wood Whites go A-Courting!

Wood white (Leptidea sinapis) butterflies courting - male on the left waving his proboscis back and forth
Wood white (Leptidea sinapis) butterflies courting – male on the left waving his proboscis back and forth

In 1988, it was discovered that the Wood White butterfly (Leptidea sinapis (Linnaeus, 1758)) was actually two species, largely overlapping in their habitats, but virtually identical and only distinguishable by microscopic observation of their genital! (3) These so-called cryptic species are widespread in their distribution and occur together throughout the European continent, from the Iberian Peninsula to the Urals (1). Some researchers went back over their collection of museum specimens to separate the two species which were once considered as one! (1)

Wood white on common vetch
Wood white on common vetch (with ant)

Unfortunately, Réal’s wood white – as the new species (Leptidea reali (Reissinger, 1989) is called – has not been found in Britain, although it was found in Ireland in 2001, where it turns out to be commoner and far more widespread than its sister species (L. sinapis). (2) It also occurs in northern and NE Spain (it was discovered in the Pyrenees).

The photographs in this blog were all taken in NW Spain (Galicia); so it is possible that they feature Réal’s wood white, but since I did not capture and dissect them (!), I will never know; which is OK by me. Réal’s Wood White has apparently been described as being a stronger flier and with a preference for more open habitats (2), which was certainly the case with the ones I photographed in Spain (below).

Wood white (Leptidea sinapis) on nectaring on Common vetch in Galicia, Spain
Wood white (Leptidea sinapis) on nectaring on Common vetch in Galicia, Spain

If all this was not exiting enough, in 2011 Réal’s Wood White was itself split! A third species – called the Cryptic Wood White (L. juvernica stat. nov.) – was discovered, based on molecular (mitochondrial and nuclear DNA) markers. (3). So there are now, three so-called ‘sibling’ Leptidea species in Europe. Amazingly, the molecular work allows the scientists to make the claims that they all evolved in the last 270,000 years with a divergence into L. sinapis and L. reali about 120,000 years ago (3). All very recent in geological terms. Unfortunately, the third cryptic species is not found in Britain either (has it been overlooked?) but does occur in Ireland. (3)

Anyway, enough of this preamble, what concerns me in this blog is the behaviour of these attractive little butterflies. My fascination started when I captured some interesting behaviour in a lucky snap I took with a compact camera. I published the picture on my blog in 2014, although I was not sure what was going on (4). I should have guessed it was courtship behaviour. It turns out that quite a lot is known about these Wood Whites which have a characteristic courtship display where the male lands opposite the female and sways his head and waves his antennae backwards and forwards with his proboscis extended (5). I was fortunate to capture the proboscis being waved by the male (below).

Wood white (Leptidea sinapis) butterflies courting detail showing male waving proboscis
Wood white (Leptidea sinapis) butterflies courting detail showing male waving proboscis

Charmingly, the male does not attempt to mate with the female until she has shown some sign of accepting his advances, which she does by lowering her abdomen so that it becomes visible between her wings. (6) She also bends her antennae backwards until they touch her wings (5). Perhaps emitting some sort of pheromone as well. I guess this all means ‘come and get me’! His behaviour has been called  ‘non-insistent’ and her signal to him was called a ‘mating willingness’ signal (6). Isn’t science full of wonderful terminology!

One way of telling the sexes apart in this species (rather these species) is via their antennae. The males have a large patch of white scales on the underside of the antennae, as shown in the illustration taken from Friberg et al. (2008).

Fig. 2 from Friberg et al, 2007. Schematic picture of a male and female Leptidea antenna. (Illustration: Moa Lönn). Springer Press.
Fig. 2 from Friberg et al, 2007. Schematic picture of a male and female Leptidea antenna. (Illustration: Moa Lönn). Springer Press.

The difference in the antennae can also be made out in my snapshot (below) where I have highlighted the different lobes of the male and female (below). The males of both L. sinapsis and  L. reali have a large patch of white scales on the underside of the antennae whilst females only have a few white scales in the midpart of the antenna. (7) Perhaps these white waving wands have the desired effect!

Wood white (Leptidea sinapis) butterflies courting; with antennal tips highlighted. Male on the left.
Wood white (Leptidea sinapis) butterflies courting; with antennal tips highlighted. Male on the left.

Another fascinating detail is that some females waited for over 11 minutes of courtship behaviour by the male – that’s a lot of antennae and proboscis waving by the male! – before giving him the ‘come hither’ signal. Whilst other ladies were happy to give him the nod after only a few seconds! (6) Already mated females were courted for up to 35 minutes by eager males, without them giving any sort of signal; it’s hard not to anthropomorphise! The act of mating itself is quite long-lasting: between 25 and 55 minutes, before the male releases himself from the act of copulation and flies away (5).

The situation is further complicated by the fact that the males do not seem to be able to determine which species they are courting. In other words, they don’t know if she is a L. sinapsis or a L. reali , which means that they can waste a lot of time and effort chatting up the wrong girl! (6). Rather unfairly, it seems that she can tell whether the male is of the same species as herself. All of this confusion is thought to be due to the fact that the species have only recently split apart. They have only had a quarter of a million years to get to know each other!

Links and references

  1. Sachanowicz, K., Wower, A., & Buszko, J. (2011). Past and present distribution of the cryptic species Leptidea sinapis and L. reali (Lepidoptera: Pieridae) in Poland and its implications for the conservation of these butterflies. European Journal of Entomology108(2), 235.
  2. http://www.wikiwand.com/en/Leptidea_reali
  3. Dincă, V., Lukhtanov, V. A., Talavera, G., & Vila, R. (2011). Unexpected layers of cryptic diversity in wood white Leptidea butterflies. Nature communications, 2, 324.
  4. https://rcannon992.com/2014/01/03/fancy-meeting-you-here/
  5. Wiklund, C. (1977). Courtship behaviour in relation to female monogamy in Leptidea sinapis (Lepidoptera). Oikos, 275-283.
  6. Friberg, M., Vongvanich, N., Borg-Karlson, A. K., Kemp, D. J., Merilaita, S., & Wiklund, C. (2007). Female mate choice determines reproductive isolation between sympatric butterflies. Behavioral Ecology and Sociobiology62(6), 873-886.
  7. Friberg, M., Bergman, M., Kullberg, J., Wahlberg, N., & Wiklund, C. (2008). Niche separation in space and time between two sympatric sister species—a case of ecological pleiotropy. Evolutionary Ecology22(1), 1-18.

“Did you hear that?” Said the butterfly.

Blue morpho (Morpho peleides) and Owl butterfly (Caligo atreus)
Blue morpho (Morpho peleides) and Owl butterfly (Caligo atreus)

It used to be thought that butterflies could not hear; that they were deaf. Well I suppose it is understandable, as they do not have ears sticking out from their tiny heads! But it turns out that they can hear – at least some of them can – and they do have ears, but not where you might think. As we shall see, they are on the base of the fore-wings.

It’s long been known that moths (and some butterflies)  have ears which are sensitive to ultrasound – high frequencies above our audible range – and that this trait probably evolved separately numerous times in the family Lepidoptera. Night-flying moths use their high-frequency hearing to detect bats and there is an evolutionary sound war – driven by natural selection – going on between these two nocturnal contestants: predator and prey. The so-called tympanal ears of noctuoid moths, such as the one shown below which I snapped in Thailand, are located on the side of moth (the metathorax) and are said to be tuned to respond to the ultrasonic calls of insectivorous bats.

Asota plana plana (Erebidae). Moths like this have tympanal ears at the junction between the thorax and abdomen.
Asota plana plana (Erebidae). Moths like this have tympanal ears at the junction between the thorax and abdomen.

Butterflies in contrast, evolved into day-flying species, with no need to be able to echo-locate bats like their ancestors did. They have grown bat-deaf! What would be useful for them though, is a way of detecting their daytime predators: birds. It seems that the old bat-detecting ears ears have been adapted to this new purpose in some species like the Blue Morpho butterfly (Morpho peleides).

blue-morpho-morpho-peleides-feeding-on-oranges in a butterfly house
Blue Morpho (Morpho peleides) feeding on oranges in a butterfly house

Ear-like structures have long been noticed at the base of the wings in some nymphalid butterflies. This tiny structure is called Vogel’s Organ. In the Blue Morpho butterfly (shown below) it is an oval-shaped structure composed of inner and outer membranes, which it has been suggested, might allow it to hear two different types of sound frequencies (high and low). It is possible that these butterflies might be ‘listening to the flight sounds of avian predators’ (Lane et al., 2008) and M. peleides may use its two membrane ‘ear’ to ‘detect both singing and flying birds’ (Lucas et al., 2009). It’s not proven yet, but the fact that these butterflies can hear in the range which covers the lower frequency sounds associated with the flapping of bird wings, provides good circumstantial evidence for a putative bird detection system, which can be tested in future experiments (Link 1).

Blue morpho (Morpho peleides) with Vogel's organ at the base of the forewing
Blue morpho (Morpho peleides) with Vogel’s organ at the base of the forewing

The owl butterfly, Caligo eurilochus, also has an ear on the base of its forewings, but according to researchers it is a simpler structure than in the Blue Morpho butterfly. The C. eurilochus ear was most sensitive to sound at frequencies between 1 and 4 kHz, similarly the M. peleides Vogel’s organ is most sensitive to sounds between 2-4 kHz. These could be used to detect the low-frequency components of approaching birds. In other words, they are bird detectors.

Owl butterfly (Caligo atreus) feeding on oranges in a butterfly house
Owl butterfly (Caligo atreus) feeding on oranges in a butterfly house

The owl butterfly is crepuscular, which means that it is most active around dawn and dusk, i.e. during low-light conditions. The ear – or Vogel’s Organ – in C. eurilochus is said to be rather anatomically simple, in comparison to the Blue Morpho.

Owl butterfly (Caligo atreus) - approximate location of Vogel's organ
Owl butterfly (Caligo atreus) – approximate location of Vogel’s organ

We usually know if an animal like a dog or cat can hear us, because it responds in some way to what we say. But it is not easy working out whether something like a butterfly can hear, even if you can find what appears to be its ears.  And when you do work out that they can hear some sounds, it’s not easy to know exactly what they are listening too, and why.

Some butterflies known the ‘crackers’ – Hamadryas spp. – emit surprisingly loud clicks, or ‘clacks’! The clicking or clacking sounds – take your pick – is mostly, but not exclusively, made by males.

Epinome cracker (Hamadryas epinone) from Argentina
Epinome cracker (Hamadryas epinone) from Argentina

A study of the beautiful blue cracker, Hamadryas feronia, in Venezuela, by Jayne Yack (Link 2) and others (2000 paper) at Carleton University (Ottawa, Canada), showed that the males made the ‘sharp clicking sounds’ during chases involving both other males, and females. Typically, a male resting or perching, on the trunk of a tree will take off and fly after another butterfly of the same species as it flies past. If it is another male, they pursue each other, making clicks when they are close to one another. If the male ends up chasing a female, then he ends up conducting what the researchers described as an ‘on-the-wing pendulous display involving continuous clicking’ for the benefit of the female! If she is receptive, then he lands and copulates with her.

Epinome cracker (Hamadryas epinone) puddling
Epinome cracker (Hamadryas epinone) puddling

So it seems that there is a lot more to learn about the sound worlds of butterflies. It is very exciting to think that there may be more complex acoustic interactions going on between butterflies and their avian predators than we ever imagined. So much research has been carried out on the visual markings of butterflies, but it may be that they also rely on sound as well as startling images on their wings to help them avoid the depredations of birds.

All photographs taken by myself either in Argentina or Amsterdam Zoo butterfly house.

Links

  1. http://io9.gizmodo.com/now-we-know-why-butterflies-evolved-to-have-ears-1152166029
  2. https://carleton.ca/biology/people/jayne-yack/

Relevant references

Lucas, K. M., Windmill, J. F., Robert, D., & Yack, J. E. (2009). Auditory mechanics and sensitivity in the tropical butterfly Morpho peleides (Papilionoidea, Nymphalidae). Journal of Experimental Biology, 212(21), 3533-3541.

Lucas, K. M., Mongrain, J. K., Windmill, J. F., Robert, D., & Yack, J. E. (2014). Hearing in the crepuscular owl butterfly (Caligo eurilochus, Nymphalidae). Journal of Comparative Physiology A, 200(10), 891-898.

Conner, W. E., and A. J. Corcoran (2012). Sound Strategies: the 65-million-year-old battle between bats and insects Annual Review of Entomology 57: 21-39.

Ribarič, D., & Gogala, M. (1996). Acoustic behaviour of some butterfly species of the genus Erebia (Lepidoptera: Satyridae). Acta entomologica slovenica, 4(1), 5-12.

Vogel R. 1912. Uber die Chordotonalorgane in der Wurzel der Schmetterlingsflugel. Z Wiss Zool 100:210–244.

Yack, J. E., Otero, L. D., Dawson, J. W., Surlykke, A. & Fullard, J. H. (2000). Sound production and hearing in the blue cracker butterfly Hamadryas feronia (Lepidoptera, Nymphalidae) from Venezuela.Journal of Experimental Biology203(24), 3689-3702.

Yack, J. E. (2004). The structure and function of auditory chordotonal organs in insects. Microscopy research and technique, 63(6), 315-337.