Bee-flies: the dipteran narwhals

White-tailed bee-fly (Bombyliidae) showing wing venation
White-tailed bee-fly (Bombyliidae), possibly Bombylius posticus, showing wing venation

I always enjoy seeing bombyliids (bee-flies). They sound like little helicopters, hovering and buzzing about, and their furry appearance gives them a certain cuteness. They are flies pretending to be bees!

Not the easiest of insects to identify from photographs though. This one looks rather like Bombylius posticus, which has a wide Palaearctic distribution, but I am not sure if it is found in northern Thailand, where I took the photograph. This species has prominent white tufted scales at both the base and apex of the abdomen. (1). Alternatively, it might be a variant of Bombylius major, which is found in Thailand.

White-tailed bee-fly (Bombyliidae), possibly Bombylius posticus, showing white scales
White-tailed bee-fly (Bombyliidae), possibly Bombylius posticus, showing white scales

Why would they want to mimic bees? One reason might be that they avoid predation by other insects which think that they are bees, i.e. armed with a harmful sting. Although they don’t have a stinging apparatus like a bee, they do have a very prominent, needle-like proboscis sticking out in front of their heads. They use this stiff, unretractable organ to penetrate and probe flowers for nectar. It almost looks like they are carrying a little spear or javelin; the dipteran equivalent of a narwhal! According to Wikipedia, some people in East Anglia call them beewhals. (2)

Bee=fly (Bombyliidae) in flight, showing proboscis sticking out in front
Bee-fly (Bombyliidae) in flight, showing proboscis sticking out in front

Another reason why they might benefit from resembling bees, is that they lay their eggs in the nests of bees and wasps. Indeed, they actually flick their eggs into the nests of some solitary bees, whilst hovering above the nest opening. (See links 3 and 4 for videos of this behaviour). Flicking, or shooting eggs from a safe distance, as one blogger aptly put it! (5) The tufts at the end of the abdomen are reportedly used to collect dust prior to flicking the eggs, something that would be fascinating to watch!

The bee-fly larvae are ectoparasitic, meaning that they attach onto the outside of the bee larvae in order to feed on their body fluids. Perhaps their bee-like appearance helps the adult bee flies get close to bees nests without being attacked? Different species are also parasites, and hyper-parasites, on a wide range of insects, including butterflies, grasshoppers, wasps, other flies, beetles and cockroaches!

White-tailed bee-fly (Bombyliidae) resting.
White-tailed bee-fly (Bombyliidae) resting.

The adults feed on pollen and nectar and are important pollinators, indeed some plants species depend upon them for their survival. There is a nice little blog about bee-flies in a Scottish garden (6).

  1. http://diptera.info/forum/viewthread.php?thread_id=61710
  2. https://en.wikipedia.org/wiki/Bombyliidae
  3. http://www.brc.ac.uk/soldierflies-and-allies/bee-flies
  4. http://abugblog.blogspot.co.uk/2015/04/awesome-bee-flies.html
  5. https://livingwithinsects.wordpress.com/2012/04/22/bee-fly/
  6. http://www.leavesnbloom.com/2012/04/bombylius-major-bee-fly-aerodynamics.html

Stingless bees and resin bugs

Stingless bees (Trigona sp.) emerging from trumpet-shaped nest entrance below dipterocarp tree
Stingless bees (Trigona sp.) emerging from trumpet-shaped nest entrance below dipterocarp tree

The peculiar shape of this nest entrance caught my eye. Bees were moving in and out of the trumpet-shaped nest which was located below a large dipterocarp tree, at the foot of Doi Chiang Dao mountain, north of Chiang Mai, Thailand.

Stingless bees (Trigona sp.) emerging from trumpet-shaped nest entrance
Stingless bees (Trigona sp.) emerging from trumpet-shaped nest entrance

These waxy nests are constructed by stingless bees (Meliponini tribe of the family Apidae), a large group of eusocial insects – meaning they live together in colonies with a queen and have different castes – which play an important role in the pollination of crops and wild flowers in tropical countries. Thirty species of stingless bees in the genus Trigona, have been recorded in Thailand; T. collina is the most common species in the north of the country. (1)

Stingless bees (Trigona sp.) emerging from trumpet-shaped nest entrance
Stingless bees (Trigona sp.) emerging from trumpet-shaped nest entrance

As the name implies, stingless bees lack a functional sting, but they have powerful jaws and will aggressively defend their nests against intruders. Non-foraging bees near the nest entrance are there to protect the nest from a range of insects including parasites – which might try to enter. They also deposit fresh resin on the external entrance tubes, in order to deter ants, which are important predators of the bees. (2)

Stingless bees (Trigona sp.) at nest entrance
Stingless bees (Trigona sp.) at nest entrance

The nests of stingless bees are usually associated with a living tree, either in a cavity in the trunk or at the base of the tree, as in this case. The nest architecture is extremely variable between species, but the shape of the external nest entrance, as well as the internal nest features, are often characteristic of a given species. When nests come under attack, hovering bees emerge in force to defend the colony: they ‘face the nest entrance, and engage in aerial fights with non-nestmates, or directly attack larger animals, which retreat with a cloud of defending bees surrounding the head’ (2).

Stingless bees (Trigona sp.) at nest entrance
Stingless bees (Trigona sp.) at nest entrance

Based on looking at different photographs posted on the Internet, the trumpet-shaped nest opening looks like it might be that of Tetrigona binghami (Schwarz, 1937), also called Trigona apicalis variety binghami Schwarz 1937, although this species was only described for the first time in 2005, in Thailand. (1) Such an identification can only be tentative as there is no definitive key available online that I am aware of. The bee’s nest was located near the base of a huge dipterocarp tree, Dipterocarpus alatus, which was festooned with epiphytes.

Dipterocarpus alatus, Chiang Dao
Dipterocarpus alatus, Chiang Dao

Stingless bees live in colonies of somewhere between a few hundred to several thousand individuals. They usually visit many different types of flowers although some species seem to be fairly host specific. The main host plant of T. binghami is said to be teak (Tectona grandis), whereas T. collina has a number of different host plants, including the large dipterocarp resin tree, Dipterocarpus alatus. (1) These trees often have a sort of scar – a tapping hole or resin trap – in the trunk, not far off the ground, that exudes an oily resin.

Resin trap on dipterocarp tree trunk
Resin trap on dipterocarp tree trunk

The resin has a number of traditional uses, including: wood lacquering, drought-proofing of boats, water-proofing of baskets and traditional medicine.  Tapping involves cutting a hole into the trunk of the tree and using fire to stimulate a continuing flow of resin. Tapping can be sustainable, but it depends upon the skill of the tapper. (4) In sites like this one, in Chiang Dao, where these dipterocarps are the only remnants of a cleared forest, the trees will probably be more susceptible to damage and their loss as a shade would be a severe blow to the resorts and houses which exist underneath their wonderful boughs.

Stingless bees (Trigona sp.) hovering above the resin trap
Stingless bees (Trigona sp.) hovering above the resin trap

Stingless bees are called ‘channarong’ in Thai. Some species, such as T. laeviceps – which commonly occurs in suburban areas – are kept by beekeepers for their honey, which is slightly more watery and acidic than western honeybee honey (3). It also ferments. The process of keeping stingless bees is known as meliponiculture.

Stingless bees (Trigona sp.) hovering above the resin trap
Stingless bees (Trigona sp.) hovering above the resin trap
Stingless bees foraging in the resin
Stingless bees (Trigona sp.) foraging in the resin
Ants on dipterocarp tree
Ants on dipterocarp tree

Also lurking in and around the resin trap were a number of so-called resin bugs. These carnivorous assassin bugs (Family: Reduviidae; Subfamily: Harpactorinae; Tribe: Ectinoderini) coat their front legs with sticky tree resin and use this to attract and trap insect prey such as the stingless bees; a strategy called sticky trap predation. Some authors have called them living fly-paper (or bee-paper) or bee-assassins (South American genera). They really are quite strange looking insects and move very slowly.

Resin bug (Reduviidae; Harpactorinae; Ectinoderini), Chiang Dao
Resin bug (Reduviidae; Harpactorinae; Ectinoderini), Chiang Dao

There are said to be 20 species in the Ectinoderini tribe of resin bugs: ten Amulius spp.; and ten Ectinoderus spp.. The species shown here is similar in appearance to Amulius malayus but I have not been able to confidently identify it.

Resin bug (Reduviidae; Harpactorinae; Ectinoderini), Chiang Dao
Resin bug (Reduviidae; Harpactorinae; Ectinoderini), Chiang Dao

There were also one or two smaller assassin bugs, the nymphal stages of the resin bugs, which also looked to be efficient predators (below).

Resin bug nymph
Resin bug nymph

There was a very attractive spider located near the top of the resin trap.  This orb spider, Argiope pulchella, builds a web with a zig-zag stabilimentum (below). It has weaved together its web to create a much denser and thicker X-shaped cross. The spider aligns its legs against the X-shaped stabilimentum, two legs against each arm of the cross. This presumably acts to camouflage, or hide the spider whilst it is sitting on the web, and perhaps the X-shape also attract flying insects into the web. The spider moves off the cross when attending to a catch.

Argiope pulchella, builds a web with an X-shaped stabilimentum
Argiope pulchella, builds a web with an X-shaped stabilimentum

There are probably many other insects attracted to the resin trap, including moths and other sap-sucking species.  It is a fascinating little ecosystem, if that is the right word, and once again a system that is ripe with opportunities for further research.

  1. Klakasikorn, A., Wongsiri, S., Deowanish, S., & Duangphakdee, O. (2005). New record of stingless bees (Meliponini: Trigona) in Thailand. Nat Hist J Chulalongkorn Univ, 5, 1-7.
  2. Roubik, D. W. (2006). Stingless bee nesting biology. Apidologie, 37(2), 124.
  3. Chuttong, B., Chanbang, Y., & Burgett, M. (2014). Meliponiculture: Stingless Bee Beekeeping In Thailand. Bee World, 91(2), 41-45.
  4. Ankarfjard, R. (2000). Ïmpacts from tapping oleoresin from dipterocarpus alatus on trees and timber value in LAO PDR. submitted to the Journal of Economic Botany.
  5. Zhang, J., Weirauch, C., Zhang, G., & Forero, D. (2015). Molecular phylogeny of Harpactorinae and Bactrodinae uncovers complex evolution of sticky trap predation in assassin bugs (Heteroptera: Reduviidae). Cladistics.

Knot bad for bees!

Japanese knotweed (Fallopia japonica) in flower in Scarborough on 13 Sept 2016
Japanese knotweed (Fallopia japonica) in flower in Scarborough on 13 Sept 2016

Japanese knotweed (Fallopia japonica) is a fast growing, invasive perennial with a terrible reputation for spreading and excluding other native plants. Its roots are also capable of breaking through concrete and other man-made materials (1).

Japanese knotweed (Fallopia japonica) in flower in Scarborough on 13 Sept 2016
Japanese knotweed (Fallopia japonica) in flower in Scarborough on 13 Sept 2016

But it’s not all bad! It looks quite nice when it is flower, right now in September, and it’s good for bees and insects. Another blogger beat me to the excellent title ‘knotty but nice’ (2) and there is a lot out there on the Web on it’s good-for-beeness!

Honey bee on Japanese Knotweed flowers
Honey bee on Japanese Knotweed flowers

There seems to be some debate on bee fora (forums) about the tastiness of Knotweed honey, which is sometimes sold as ‘bamboo honey’ in the US apparently. I’d like to try it; bet it’s nice.

Honey bee on Japanese Knotweed flowers
Honey bee on Japanese Knotweed flowers
  1. http://www.knotweed-uk.com/Japanese-knotweed-Guidelines.html
  2. http://honeybeesuite.com/knotty-but-nice-for-bees/

Asian hornet in Galicia

 Asian hornet or yellow-legged hornet (Vespa velutina), on bell heather
Asian hornet or yellow-legged hornet (Vespa velutina), on bell heather

At the end of last month (on 28th August) I sat on a hillside in Galicia, Spain, next to a beautiful bush of flowering bell heather, photographing the wasps which were gorging themselves on the pollen and nectar. They were covered in pollen (below).

Vespa velutina on bell heather
Vespa velutina on bell heather

They were very calm and non-aggressive and I sat right next to them for some time. I did not realise at they time that I was photographing the Asian hornet or yellow-legged hornet (Vespa velutina), and not a native species.

Vespa velutina on bell heather, above Cariño in Galicia, Spain
Vespa velutina on bell heather, above Cariño in Galicia, Spain

The site was near a beautiful lookout point called Mirador do Miranda en Cariño above the town of Cariño (below).

Looking down on the town of Cariño, Ria Ortigueira, Galicia, Spain
Looking down on the town of Cariño, Ria Ortigueira, Galicia, Spain
Asian hornet or yellow-legged hornet (Vespa velutina), on bell heather
Asian hornet or yellow-legged hornet (Vespa velutina), on bell heather

It was only when I saw the impressive nest of this invasive species in the local museum in Ortigueira, did I realise that I had been watching the Asian hornet.

Asian hornet nest
Asian hornet nest

There are many different subspecies of Vespa velutina in Asia but the one that invaded Europe in 2004 and is spreading through France and Spain, is Vespa velutina nigrithorax. (1, 2). This wasp is actually smaller than the European hornet Vespa crabro, but it is a major threat to European honey bees (Apis mellifera), which unlike Asian honey bees (Apis cerana) – which evolved in the presence of this predator – do not have any defense against the Asian hornet. Our poor bees do not know how to cope with an attack by the Asian hornet. Unlike the Asian honeybees, which make a ‘very fast bee-line for the hive entrance to avoid the jinking wasps’, poor old A. mellifera ‘slows down and sashays in the face of wasps.’ (3) And although our honey bees can kill native predatory hornets by ‘heat-balling’ – surrounding them in a mass of bees – they fail to kill the Asian hornets. The Asian honey bees have ‘learnt’ how (evolved a way) to do so using a temperature higher than A. mellifera and with more balling bees. (4)

Vespa velutina drinking water by the Rio Sor, Galicia, Spain
Vespa velutina drinking water by the Rio Sor, Galicia, Spain

This insect was first detected in Galicia in 2013 and appears to have significantly spread and colonized new areas in the past few years. It is reassuring to see that much is being done to try to minimize the impact of this pest and there is some excellent information available online (in Spanish) including a pest management programme. (5) The widespread presence of the Asian hornet in this area is however, very worrying.

It seems that the pest is now very well established in northern Spain and is surely impossible to eradicate. In South Korea, where V. velutina also invaded and is now well established, it has rapidly displaced native hornets and become the dominant species in urban areas. (6). That is a very worrying prospect for European countries and a lot of work needs to be done, especially on the ecological effects on native species, as this Asian hornet feeds very wide range of insects, including flies, dragonflies and grasshoppers. It is really quite concerning, not just for honey bees, whose hives can be protected – by reducing the hive entrance to a narrow slit – to keep out the invasive hornet, but for native insect species.

Vespa velutina drinking water by the Rio Sor, Galicia, Spain
Vespa velutina drinking water by the Rio Sor, Galicia, Spain

There are some fantastic pictures of Asian hornets attacking a bee hive on this site called The Bee photographer (7).

  1. https://en.wikipedia.org/wiki/Asian_predatory_wasp
  2. Monceau, K., Bonnard, O., & Thiéry, D. (2014). Vespa velutina: a new invasive predator of honeybees in Europe. Journal of pest science, 87(1), 1-16.
  3. Tan, K., Radloff, S. E., Li, J. J., Hepburn, H. R., Yang, M. X., Zhang, L. J., & Neumann, P. (2007). Bee-hawking by the wasp, Vespa velutina, on the honeybees Apis cerana and A. mellifera. Naturwissenschaften, 94(6), 469-472.
  4. Tan, K., Wang, Z., Li, H., Yang, S., Hu, Z., Kastberger, G., & Oldroyd, B. P. (2012). An ‘I see you’prey–predator signal between the Asian honeybee, Apis cerana, and the hornet, Vespa velutina. Animal Behaviour, 83(4), 879-882.
  5. http://mediorural.xunta.gal/es/areas/ganaderia/apicultura/vespa_velutina/
  6. Choi, M. B., Martin, S. J., & Lee, J. W. (2012). Distribution, spread, and impact of the invasive hornet Vespa velutina in South Korea. Journal of Asia-Pacific Entomology, 15(3), 473-477.
  7. http://thebeephotographer.photoshelter.com/gallery/Asian-Hornet-the-bee-killer/G0000H7PH.GP.HVY

What doesn’t kill you, doesn’t always make you stronger! If you are a bee.

Some pyrethroid insecticides have in the past been considered safe for bees because they have a repellent effect which is thought to keep the bees away from insecticide-covered flowers. The chemical drives them off. But it has been known that when pyrethroids are applied in the presence of foraging bees this results in a reduction in their activity (1). Scientists have now found that the affected bees slow down markedly, travel less and spend less time interacting with other bees – vital for bee colonies. They used video-tracking software to quantify these differences in bee behaviour (2).

In the USA, honey bees are carted about the country in vast numbers, to ‘service’, i.e. pollinate, a wide variety of crops like almonds, sunflowers, oil seed rape, apples, grapes and so on. Most crops in fact. A market that was worth an estimated $626 million dollars in 2012 (USDA: Link 3).

The bees didn’t get a penny! In fact, nearly 40% of these American colonies died off last year (2015), although they are quickly replaced with new ones (4). Many of the colonies are placed in orchards which have been sprayed with pyrethroids. Over one million acres of U.S. orchards are sprayed with pyrethroids (5). Whilst the bees are not killed outright by the insecticides, it is now becoming clear that they suffer sub-lethal effects. And although these effects don’t kill them, they definitely don’t make the bees stronger either! Although the link is not proven, it does not seem surprising to me that many of them die after suffering this stress, particular if they experienced heavy doses; together with the additional stress of being transported for thousands of miles on the back of lorries (3).

This study carried out in Nebraska, showed that the effects of the chemicals we put into the environment can be subtle; more subtle that was at first thought and shows that the risks need to be assessed carefully to pick up these sort of low-level effects. In this case it took careful experiments using video-tracking and computer software to quantify differences that might not be obvious to the unaided eye. After all, we can’t ask the bees how they are feeling! Or more accurately, they cannot reply.

It would of course be better if all of our crops round the world were pollinated by native wild pollinators; some of them are, but we need a more sustainable type of agriculture that focuses more on the impact of farming practices on the environment and less on maximizing profit. But farmers have to make a living and we might have to pay more for such a system? Or accept less production. In the meantime, spare a thought for the bees which gave their lives so that we can could enjoy our Californian grapes and cherries!

  1. http://www.agro.basf.co.za/agroportal/za/media/l6/productcatalogue/products/insekdoders/fastac_sc.pdf
  2. Ingram, E. M., Augustin, J., Ellis, M. D., & Siegfried, B. D. (2015). Evaluating sub-lethal effects of orchard-applied pyrethroids using video-tracking software to quantify honey bee behaviors. Chemosphere, 135, 272-277.
  3. http://www.ers.usda.gov/media/1679173/special-article-september_-pollinator-service-market-4-.pdf
  4. http://www.globalresearch.ca/death-and-extinction-of-the-bees/5375684
  5. https://entomologytoday.org/2015/05/29/pyrethroid-insecticides-alter-honey-bee-behavior/

Bees knees and tongues!

Bombus hortorum on sea clover, Galicia, Spain
Bombus hortorum on sea clover showing long tongue or proboscis, Galicia, Spain

Since it’s Bees Needs week, I thought that I would put together a blog about bees using photographs I have taken recently in Scarborough and Spain. Taking photographs of bees is fun, but it is a bit of a hit and miss process and you need to take quite a lot of shots to get some good ones. Well at least I do! One thing that strikes one when looking at photographs of bees feeding (nectaring) on flowers, is their tongue, or proboscis. In the following photo, a common carder bee does not look like it is having any problem obtaining nectar from a Birds-foot-trefoil flower, but it might be challenged by flowers with long corollas (the tube leading down to the nectar).

common carder bee (Bombus pascuorum) on Birds-foot-trefoil
Common carder bee (Bombus pascuorum) on Birds-foot-trefoil, UK

The bumblebee tongue or proboscis is a complex organ which consists of a tongue proper – with a hairy or feathery end adapted for absorbing nectar – sheathed in a pair of palps and the maxilla (1). For a fantastic close-up photograph of a bumblebee tongue, click on the link below (link number 2) to the site of macro photographer, Adrian Thysse. The Early bumblebee, in the following photograph, has a relatively short tongue compared to some other species, but it still looks quite long in this image.

Early bumblebee (Bombus pratorum) with tongue showing
Early bumblebee (Bombus pratorum) with tongue showing

The hard, shiny maxilla which sheathes the tongue can be seen in the following photograph of a Garden bumblebee, Bombus hortorum. The tongue can be well over one centimeter long in this species (see below).

Bombus hortorum proboscis or tongue. Galicia, Spain.
Bombus hortorum proboscis or tongue. Galicia, Spain.

Bumblebees with long tongues are in general able to access nectar from a greater variety of flowers than those with short tongues, and as a consequence they feed on a larger number of species (3), assuming that they are available in a given habitat. The long-tongued bumblebees have also been found to forage significantly faster than bees of shorter proboscis length on flowers with long corolla tubes (4). Bumblebees with shorter tongues, not surprisingly perhaps, preferred to forage on flowers with short corolla tubes and were more efficient at getting nectar from them.

Common Carder Bee (Bombus pascuorum) on Sea vetch
Common Carder Bee (Bombus pascuorum) on Sea vetch

Relative tongue lengths of worker bumblebees are shown in the following table taken from the www.bumblebee.org site (1), although it is worth remembering that the glossa is a flexible and somewhat elastic organ. The data come from Brian (1957) I think (5).

Species

Tongue length mm

Bombus hortorum

12.0

Bombus lapidarius

6.0

Bombus pascuorum

7.6

Bombus pratorum

6.4

Bombus terrestris/lucorum

5.8

As well as having different tongue lengths and visiting a different range of flowers, bumblebees of different species have been found to collect a different range of pollen (6). The pollen is carried in a pollen sac, or pollen basket, which is just a flat area on the leg surrounded by a cage of spiky hairs. I am always impressed how bumblebees are seemingly able to multitask: feeding on nectar at the front end; walking with their forelegs; and scraping/combing pollen towards the basket on the rear legs, with their middle legs! The sacs of pollen look so large sometimes, the aerodynamics of the bee must change depending on whether the pollen basket is full or empty!

White-tailed bumblebee (Bombus lucorum) with pollen sac landing on kidney vetch
White-tailed bumblebee (Bombus lucorum) with pollen sac landing on kidney vetch

Another White-tailed bumblebee (below) has an empty pollen sac, and it is possible to see the fringe of hairs on the hind leg, which form the basket.

White-tailed bumblebee (Bombus lucorum) showing an empty pollen basket
White-tailed bumblebee (Bombus lucorum) showing an empty pollen basket

Another feature which sometimes becomes apparent when taking photographs of bumblebees, is the presence of tiny mites clinging on to their bodies. One can be seen, just under the wing, in the following photograph of a Common carder bumblebee.

Common Carder Bee (Bombus pascuorum) with phoretic mite highlighted
Common Carder Bee (Bombus pascuorum) with phoretic mite highlighted

These are generally assumed to be fairly harmless, in that although they live in bumblebee nests, they only feed on the detritus, wax, pollen and rubbish discarded by the bees! They use the bees as a form of transport and can get on and off as they please; a bit like getting off one bus and boarding another; the bus stop in this case, being a flower! If they cling on until the bumblebee returns to its nest, they can move home in this way. The technical term for this behaviour is called phoresis, so they are phoretic mites. They are also called commensals, which means that they are involved in a symbiotic relationship in which one species (the mites) is benefited while the other is unaffected (the bees).

Common Carder Bee (Bombus pascuorum) with mite highlighted
Common Carder Bee (Bombus pascuorum) with phoretic mite highlighted

There are of course damaging, parasitic mites, like the Varroa mite, but that is another story. The numbers of phoretic mites per bee can vary enormously and in one study ranged from one individual to over 100 per bumblebee (8); 200 per bee in another (9). Why some bees have so many, and what it means for them in terms of their health and fitness is something that is being studied, and my guess is that there is more to this relationship between bees and mites than we may realise.

  1. http://www.bumblebee.org/bodyTongue.htm
  2. http://bugs.adrianthysse.com/2015/01/in-memorium-the-tongue-that-killed-my-flash/
  3. Harder, L. D. (1985). Morphology as a predictor of flower choice by bumble bees. Ecology, 66(1), 198-210.
  4. Inouye, D. W. (1980). The effect of proboscis and corolla tube lengths on patterns and rates of flower visitation by bumblebees. Oecologia, 45(2), 197-201.
  5. Brian, A. D. (1957). Differences in the flowers visited by four species of bumble-bees and their causes. The Journal of Animal Ecology, 71-98.
  6. Brian, A. D. (1951). The pollen collected by bumble-bees. The Journal of Animal Ecology, 191-194.
  7. https://www.rhs.org.uk/science/conservation-biodiversity/wildlife/encourage-wildlife-to-your-garden/plants-for-pollinators
  8. Chmielewski, W., & Baker, R. A. (2008). Mites (Acarina) phoretic on some common bumblebee species (Bombus spp.) from the Pulawy area (South-Eastern Poland). Journal of Apicultural Science, 52(1).
  9. Matias Maggi, Mariano Lucia, Alberto Abrahamovich. Study of the acarofauna of native bumblebee species (Bombus) from Argentina. Apidologie, Springer Verlag, 2011, 42 (3), pp.280-
    292.