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Odd postures !
 
There can be few members of the Lepidoptera as odd as this creature which confronted me in the rainforests of Trinidad. While walking along a trial, my attention was caught by what appeared to be a dead leaf, which seemed to have fallen and settled on green foliage. A spider appeared to be sitting in the middle of it, but somehow it all looked a bit too symmetrical, so I took a closer look...

Closer examination revealed that the "dead leaf" was in fact the wings of a moth, and the "spider" was it's body and legs.
 
It had adopted an extremely odd posture, with it's body, legs and outstretched wings held in a vertical plane, and had a strange mesmerising effect on me as I watched it. I gave it the nickname "Sit on it's bum moth". For many years I was completely mystified by the insect, but it was was finally identified 10 years later by Mike Shaffer of the British Natural History Museum, as Siculodes aurorula, a member of the Thyrididae. My specimen was the first ever recorded in Trinidad.
 
The wings are a marvellous example of camouflage - perfectly disguised as a dead leaf, complete with windows to simulate the nibblings of insects, and spotted with dark areas that could easily be mistaken for leaf mould.
 
The photograph finally revealed the reason for the incredibly long legs which had long puzzled entomologists who had studied the museum specimen. The moth needed them so that it could rest in this very odd upright posture. The pose is almost threatening. Why would a moth need to stand in such a strange position ? Perhaps when viewed from this angle it might appear sufficiently scary to frighten off a small avian or reptilian predator ? Perhaps it simply needs to raise itself clear of the substrate to avoid getting stuck to it when the leaves are wet with rain ?

Unrelated species which look identical !
The mimicry theory as postulated by Henry Bates states that by a process of evolution, a number of edible butterfly species have "mimicked" distasteful species, adopting the same colours and patterns, so that insectivorous birds that have tried to eat the unpalatable "models" will avoid attacking the edible "mimics".
By way of example, the Heliconiine genus Eueides comprises of 12 medium sized butterflies which share almost identical anatomical and morphological features, but which differ greatly in colouration and patterning. Some, like isabella appear to be mimics of orange / black banded Ithomiines, while others including aliphera and lineata are very similar to Dryas iulia in appearance. Yet others, such as vibilia, closely resemble Actinote species. Eueides heliconioides falls into yet another group that strongly resemble Laparus species. In all these cases the "models" are known to be distasteful or toxic to avian predators, while all the "mimics" are believed to be edible. This is called Batesian Mimicry.

 

Methona confusa, an unpalatable member of the Nymphalidae

( subfamily Ithomiinae ). The butterfly contains toxins that are derived from it's caterpillar's foodplants ( nightshades ), and

from adult food sources such as decomposing Heliotropium and Eupatorium flowers.

Patia orise, an edible member of the Pieridae. This species has 6 short legs, narrower forewings, and much larger hindwings. Methona has 4 very long legs, drooping antennae, and a series of tiny white spots around the wing borders.

Müller later theorised that unrelated and unpalatable butterflies also mimic each other to increase each individual species' chance of avoiding attack. Many orange / black banded species from the subfamilies Danainae, Ithomiinae, Riodinidae, Nymphalinae, Heliconiinae, Papilioninae, Dismorphiinae, Pierinae and Acraeini are so similar that they are thought to be involved in a "mimicry ring" known as the "tiger complex", in which convergent evolution has caused once dissimilar taxa to become almost identical. In some cases the males "mimic" one toxic species, while the females "mimic" another entirely different "model" !

Hiding from humans !
Butterflies do some strange things to elude attention. The Zebra Hairstreak Arawacus separata has a pattern of stripes which creates the illusion that it is facing back to front. It enhances the illusion by immediately turning to face the opposite direction as soon as it lands on a leaf. There it remains totally motionless until approached, at which point it slowly but deliberately rotates to present the observer with a view of it's posterior !

Arawacus separata.

 

The pattern of striped directs the eye towards the "false antennae" which are actually small tails on the hindwings. It reinforces the illusion that it's tail is it's head, by turning to face the opposite direction as soon as it lands on a leaf. It even jiggles it's wings slightly to make the false antennae move ! It's all part of a trick to divert bird attacks away from the head, and allow the butterfly to escape. Clever eh ?

 

Another South American species, the Mosaic Colobura dirce, spends long periods perching motionless on tree trunks. It is normally a very tame insect, allowing humans to approach closely, but if deliberately disturbed, instead of flying, it scuttles around to the opposite side of the tree trunk to hide. If the observer follows it, the butterfly runs back again, and repeated disturbance causes it to literally run around in circles in a chase around the tree trunk !

 


Strange feeding habits !

In temperate countries most adult butterflies feed on flower nectar, although some will visit sap runs, or imbibe dissolved mineral salts from dung, damp earth or carrion. In the tropics many Nymphalids feed at rotting fruit, while Swallowtails and Sulphurs prefer to drink from urine-soaked ground, and many Hesperiine skippers are noted for feeding at bird droppings. Dead fish are a popular food source for Agrias in South America, and I've seen Ithomiine Glasswings feeding on the corpses of flies.

In Malaysia, I've observed an Allotinus species feeding directly from the honey glands of aphids. In Ecuador I've watched the beautiful Junea doraete gorging itself on the corpse of a snake, and found the stunning metalmark Necyria bellona feeding on the corpse of a toad.

Blue Doctor Rhetus periander

Venezuela produced something even more interesting - the gorgeous long-tailed metalmark known as the Blue Doctor Rhetus periander, which was seen feeding on the corpse of a giant tarantula.
One of the strangest habits however is that of the brilliant orange Julia Dryas iulia, which is quite content to feed at nectar in Costa Rica, or to imbibe dissolved minerals from mud in Ecuador, but in parts of Brazil groups of these butterflies are regularly seen sipping the liquid in the corner of the eye of the yellow-throated caiman !

 
 
 
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