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Strange but true !
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Weirdest caterpillar on Earth ?
Caterpillars come in some strange
shapes, but there can be few creatures more weird-looking than this moth
caterpillar ( family Limacodidae ) from French Guiana. Note that this photo does
not depict a group of caterpillars - it is a single caterpillar which has
enormous hairy limb-like lateral extensions to each segment !
Limacodid larva, French Guyana
( image © Stéphane Brûlé )
Plants that trick
butterflies !
Caterpillars of Cattle
Heart butterflies (
Parides
) from South America feed on
Aristolochia
vines, but some vines can defend themselves by only "permitting" the butterflies
to lay a small number of eggs. If extra eggs are laid, the leaf around the egg
dies, and the dead tissue drops to the ground, carrying the egg with it !
A
similar trick is played by
Passiflora vines,
which produce stipules ( small false leaves ) at the base of leaf stems, that induce egg laying
by some species of Heliconiine
butterflies. A day or two later the stipules drop off, carrying the eggs with
them. Some other Passiflora
vines produce tiny tubercles on the stipules that mimic Heliconiine
eggs. Any butterfly visiting the plant sees the false eggs and is misled into
thinking that the plant is already overladen with eggs, so is
inhibited from adding more.
Heliconius erato, Rio Madre de Dios, Peru
Wings
with ears !
Some butterflies
can detect sound, using "ears" on the underside of their wings.
These microscopic funnel-shaped ears are covered with a very thin
membrane that vibrates in response to high frequency sound. The
ear is only present in certain butterfly families.
Some scientists
believe that all early butterflies were nocturnal, and that
the ears evolved to enable them to detect and avoid predatory bats.
Other butterfly families which do not possess ears are thought to
have evolved daytime flight as an alternative anti-bat strategy.
In
Morpho helenor the eardrum is located
at the base of the wing.
( image
© Kathleen
Lucas )
Caterpillar cannibals !
Caterpillars of the Scarce
Swallowtail Iphiclides
podalirius are
territorial. The silk trails which they lay as they walk along twigs have a
slight odour. This enables each larva to recognise it's own silk trail, and use it as a route map to
find it's way back to particularly succulent leaves. If two larvae meet, the
larger one spins a silk web around the smaller one to kill it, or bites it to
death.
Epiphile
caterpillars in South America are equipped with long sharp poisonous "antlers"
which they use to defend themselves against other insects. If disturbed they
swish their heads violently, using the antlers to puncture the skin of attacking insects. The
lepidopterist A. Muyshondt observed
Epiphile
caterpillars attacking each other, locking antlers until death.
Headless butterflies can
still fly !
In June 2010, when in the Peruvian Andes I
chanced upon a group of Diaethria butterflies
settled on the ground. Most were busily imbibing mineralised moisture from the
damp sand. One particular butterfly however was walking about, slowly fanning
its wings. I crept closer in order to photograph it, and peering through the
camera viewfinder I suddenly realised that the butterfly had no head! Despite
having been decapitated ( following an attack by a bird or a wasp? ) it was
perfectly able to walk, fan its wings and even to fly short distances!
The explanation is that insects have a nervous
system in which certain functions are not centralised on the brain. Hence
reproduction, locomotion and respiration are not dependent upon retaining a
head. This not only explains why a headless Diaethria
can walk and fly, it also explains how a male praying mantis can complete a
sequence of mating processes with a female while she is eating his head ! This
incidentally is normal behaviour
for mantises - males passively submit to cannibalism, a practice that may have
evolved because copulation duration and fertilisation success are almost doubled
when the male is cannibalised.
Diaethria clymena - walking and
fanning its wings after decapitation, Shima, Peru
Run and jump in Ghana !
In 2001, at Boabeng-Fiema
rainforest in Ghana, I observed the strange antics of a leaping caterpillar.
Crawling towards the tip of a leaf, it came to a "dead end", whereupon it
rapidly shuffled backwards a couple of inches, before taking a run and jump to
leap across to another leaf about 9 inches away. Fascinated by this
extraordinary behaviour I continued to watch as the larva repeated the process
several times to migrate across the bush.
Intelligent butterflies !
The
seemingly complex courtship rituals of many butterflies implies
that they have some degree of intelligence, but careful analysis
shows that the rituals are merely a series of instinctive
responses to specific stimuli. A female for example might react
in a particular way if approached by a male and showered with
pheromones, but the male then also has to respond in a
particular way which signals the female to initiate the next
stage in the ritual, and so on.
There is some evidence however
that certain butterflies do demonstrate intelligence and reasoning.
Experiments have proven that
Heliconius butterflies can learn home ranges within
which they can memorise the locations of nectar and pollen sources, host plants
and communal roosting sites. They are able to plan the most efficient route by
which to visit all nectar / pollen sources in the vicinity by using simple
calculations akin to what mathematicians call the "travelling salesman
algorithm".
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