Strange, but true !
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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...
examination revealed that the "dead leaf" was in fact
the wings of a moth, and the "spider" was it's body and legs.
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
a member of the Thyrididae. My specimen was the first ever
recorded in Trinidad.
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 ?
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".
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
appear to be mimics of orange / black banded Ithomiines, while others including aliphera
are very similar to Dryas iulia
in appearance. Yet others, such as
closely resemble Actinote
falls into yet another group that strongly resemble
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.
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" !
confusa, an unpalatable member of the Nymphalidae
( subfamily Ithomiinae ). The butterfly contains toxins that are derived
from it's caterpillar's foodplants ( nightshades ), and
adult food sources such as decomposing
Heliotropium and Eupatorium
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.
Hiding from humans !
Butterflies do some strange things
to elude attention. The Zebra Hairstreak
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 !
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 !
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
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.
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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