An endemic egg-fly from Sulawesi

The Sulawesi endemic egg-fly, Hypolimnas diomea Hewitson, 1861
The Sulawesi endemic egg-fly, Hypolimnas diomea Hewitson, 1861

I chased this butterfly for quite a while before it settled down on a leaf and let me take a photograph!  I did not know what it was at the time, but subsequently discovered that it is a species which is endemic to Sulawesi called Hypolimnas diomea Hewitson, 1861.  William C. Hewitson being the gentleman who first named it in a book entitled ‘Illustrations of New Species of Exotic Butterflies’.  This beautifully illustrated book is available online (1).  William Hewitson (1806–1878), was a wealthy collector of beetles and butterflies – and a very fine artist – but he relied mainly on collectors to supply him with specimens and did not visit the tropics as far as I am aware.

These butterflies usually exhibit pronounced sexual dimorphism, a fancy way of saying that the males and females look very different.  They are also often mimics – meaning that they look very similar to – milkweed butterflies (Danaids) which are poisonous to birds (or at least they spit them out and learn to avoid preying on them!).  The male of this species (H. diomea) has a lovely purple colour on the upper-sides of its wings, rather than the white of the female (shown here).  It is only the female which is a mimic in this species (2); probably of taxonomically very different butterflies called Crows, such as Euploea diocletianus and E. latifasciata, which feed on toxic milkweed plants (2).  

Hypolimnas diomea female on leaf
Hypolimnas diomea female on leaf

I came across this butterfly whilst walking along a small road near Highland Resort, about 5 miles from Tomahon (on the road to Kali village).

1) ‘Illustrations of New Species of Exotic Butterflies’, (London: 1851-1866).http://www.biodiversitylibrary.org/item/46120#page/7/mode/1up

2) R. I. VANE-WRIGHT, P. R. ACKERY and R. L. SMILES (1977).  The polymorphism, mimicry, and host plant relations of Hypolimnas butterflies. Biological Journal of the Linnean Society 9(3), 285-297.

You are so nice, I could eat you!

 Golden silk orb-weaver spider (Nephila sp.) from Sulawesi
Golden silk orb-weaver spider (Nephila sp.) from Sulawesi

I came across this huge spider on Bunaken Island, in northern Sulawesi.  The body must have been about 4 cm long and the legs spanned at least 15 cm, maybe more. It is a golden silk orb-weaving spider (genus Nephila) – also called giant wood spiders – which construct large webs to trap their prey. typically flying insects (e.g. bees, wasps and butterflies) but in some cases even small birds have been trapped and consumed!  These spiders, in the suborder Areneomorphae, have superb, pincer-like fangs; which can be seen below the head, in the upside-down position in the photo.  The tiny spiderlings can also be seen crawling over the web; they are too small to trigger a response from Mum!

 Golden silk orb-weaver spider (Nephila sp.) from Sulawesi
Golden silk orb-weaver spider (Nephila sp.) from Sulawesi

The amazing thing about these spiders is their sexual dimorphism; she is huge; he is tiny! I am not 100% sure, but I think that the male is the small red spider which can just be seen to the right of the large black female in the following photo.

 Golden silk orb-weaver spider (Nephila sp.) showing the large black female, and the tiny red male to the right.
Golden silk orb-weaver spider (Nephila sp.) showing the large black female, and the tiny red male to the right.

It is not altogether clear why the males are so much smaller, but one hypothesis is that so they can avoid been eaten by the female, who ignores such small fry!  However, the males do fight it out among themselves for access to the female and size does matter in these battles.  So it seems that there may be competing evolutionary pressures for the males to be large enough to win their fights but small enough not to get eaten (1). Curiously though, if a male does mate successfully with a female, it may be in his own interest to be consumed – now there’s commitment for you – since it can help the success of the fertilization (2) – presumably because the female is well fed!  I guess the trick is to get eaten after mating rather than before!

Oh yes, I forgot to mention that they are venomous!

1)  Mark A. Elgar and Babette F. Fahey (1996).  Sexual cannibalism, competition, and size dimorphism in the orb-weaving spider Nephila plumipes Latreille (Araneae: Araneoidea). Behavioral Ecology  7(2): 195-198.

2) Jutta M. Schneider and Mark A. Elgar  (2001). Sexual cannibalism and sperm competition in the golden orb-web spider Nephila plumipes (Araneoidea): female and male perspectives. Behavioral Ecology 12(5): 547-552.