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The butterfly
lifecycle
The Lepidoptera
( butterflies, skippers and moths ), belong to a group of insects
called Endopterygotes, all of which go through 4 distinct phases in
their lifecycles :
Section 1 - EGG
( ovum / ova )
Section 2 - CATERPILLAR
( larva / larvae )
Section 3 - CHRYSALIS
( pupa / pupae )
Section 4 - ADULT
( imago )
Larva
( continued )
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With
each successive moult, the caterpillar changes it's appearance, both
physically, and in colour and pattern. In some species, such as
Satyrine butterflies, the changes are minimal - often just a slight
change in colour so that the younger caterpillars match the shade of
the fresh young leaves on which they feed, while the fully grown larvae
become darker, matching the colour of old leaves.
In
other species, particularly amongst the Sphingidae ( hawkmoths )
Saturniidae ( wild silkmoths ), and the Nymphalidae, the changes are
more dramatic and often involve major colour changes and the
development of armature.
Armature
In some species the
caterpillar's body is naked, but other species may have thick coats of
hair-like "setae".
These make it more difficult for an avian or reptilian predator
to swallow a larva, and have the added bonus of cushioning the
caterpillar in the event of a fall.
Hair also functions to trap
pockets of air around the body, allowing the caterpillar to survive
if it has the misfortune to fall into a puddle. Experiments have
shown for example that caterpillars of the Garden Tiger moth
Arctia caja
can survive periods of several days submerged in water.
larva of
Drinker moth Euthrix potatoria (
Lasiocampidae ), England
The hairs often have
irritating properties. In the case of the Drinker moth
Euthrix potatoria
they do little more than cause a mild itch, but the hairs shed by
the larva of the Brown-tail
moth
Euproctis chrysorrhoea
are rather more troublesome and
can cause a severe rash on human skin. With these and a few other
exceptions, larvae from temperate regions of the world are fairly
safe to handle, but in the tropics there are many species which can
inflict painful stings.
Caterpillar
of an unidentified species of Flannel moth ( Megalopygidae ),
Peru. The caterpillar looks a bit like a hairy seed or nut, but
hidden beneath the soft hairs are a series of sharp spines. If the
caterpillar is handled the spines break, releasing a chemical
which causes excruciating pain.
Unidentified
moth caterpillar, Peruvian Andes.
Many
larvae, such as the unidentified species illustrated above, use
bright patterns and colours to warn enemies that they are
distasteful or poisonous. Others, including those of the Nymphalinae, Heliconiinae, Limacodidae and Saturniidae (
wild silkmoths ) are armed with rows of extraordinary multi-branched spikes
and horns which are enough to deter many birds from attacking, and
no doubt also offer a degree of protection against wasps, ants and
other insect predators.
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Pandita sinope
( Nymphalidae ) Singapore
( photo
courtesy Horace Tan
©
2008 ) |
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Lexias pardalis
( Nymphalidae ) West Malaysia
( photo
courtesy Gan
Cheong Weei
©
2008 ) |
Brenthis daphne ( Nymphalidae
) Hungary
( image
© Peter Bruce-Jones )
Spikes, hairs and other armature are
most pronounced in young larvae which feed communally, so it seems
likely that one of their functions may be to protect the individual (
and the species) against cannibalism. This theory would also
explain why the armature of these species reduces as they grow
larger, as they tend to feed solitarily in the later instars.
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In
most species the spines are harmless or cause only mild
irritation in humans, but in at least one Saturniid species the
spines produce a potentially lethal sting : The well camouflaged spiked
caterpillars of Lonomia obliqua are
often found clustered in groups of
up to 100 on the trunks of trees in Amazonia. There have been
many incidents where people have
unwittingly touched
or rubbed
their arm against groups of these caterpillars. The effects
can be
very severe, including massive intercranial
haemorrhaging and
kidney failure.
Lonomia caterpillars are a frequent
cause of death in southern Brazil - 354 people died between 1989
and 2005.
The fatality rate is about 1.7% - roughly equivalent to that of
rattlesnake bites. |
The
caterpillar of the Bullseye silkmoth Automeris
( Saturniidae ) Peru, can inflict a painful sting.
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unidentified sp,
( probably Limacodidae )
West Malaysia
( photo
courtesy Gan
Cheong Weei
©
2008 ) |
Sphinx ligustri (
Sphingidae ). Contrary to popular myth the horn of a hawkmoth
caterpillar cannot "sting"
although it's function is not known. The caterpillar is
harmless, and edible to birds.
Osmaterium
The larvae of Swallowtails and Cattlehearts ( Papilionidae ) are
armed with a defence organ behind the head. This
orange-coloured "osmaterium" normally remains hidden, but if the
larva is alarmed the organ is exposed, and malodorous butyric acid
compounds are exuded that deter
attacks from parasitoid or predatory wasps ( Hymenoptera ) and flies ( Diptera ).
Larva of Peruvian Cattleheart Parides
anchises with osmaterium extended to deter attack.
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