|
The butterfly
lifecycle
1 - Egg
- anatomy, oviposition
2 - Caterpillar
- anatomy
3 - Caterpillar
- hatching, feeding and development
4 - Caterpillar
- cannibals, carnivores and myrmecophiles
5
- Caterpillar
- survival mechanisms,
armature, camouflage / disguise
6 - Caterpillar
-
co-evolution with plants
7 - Chrysalis
- pupation, metamorphosis
8 - Adult
- emergence, feeding
9 - Adult
- mate location and courtship
10 - Adult
- daily routine, roosting, hibernation, lifespan
Larva
:
cannibals, carnivores & myrmecophiles
Cannibals
Larvae often find
themselves on plants with insufficient foliage to sustain them, so
at these times they naturally tend to wander in search of other
plants. Often it can take a considerable time for a larva to locate
another specimen of it's foodplant, and starvation sets in.
It is normal for a
starved larva to nibble intensely at any object it encounters. If
the object happens to be another larva it is likely that its skin
would be punctured, and the mouthparts of the attacker would come
into contact with its body fluids. The fluids have a similar chemical content and taste to the foodplants of the larva,
and hence cannibalism arose.
Cannibalism has two possible advantages for larvae - firstly by
eradicating competitors they ensure they have enough leaves for
themselves. Secondly, captive rearing has shown that cannibalistic
larvae grow faster than non-cannibals, probably because they save
themselves the time-consuming business of digesting and processing
the vegetation.
The larvae of many species including the
Orange tip
Anthocharis cardamines
and the Dun-bar moth
Cosmia trapezina are
cannibalistic. They normally feed on foliage but will attack and eat any
other caterpillar that they encounter. Most members of the Lycaenidae
also have very strong cannibalistic tendencies, and many are
carnivorous on aphids or ant grubs.
Carnivores
The larva of the Large Blue
Maculinea arion feeds in
its early instars on the flowers and leaves of
Thymus pulegioides,
but is aggressively cannibalistic towards other larvae.
Upon reaching the
4th instar it
loses all interest in
feeding, releases it's grip on the
foodplant and falls to the ground. It wanders about until
it is located by a Myrmica sabuleti
ant. The ant uses it's antennae to caress the larva, stimulating it
to secrete a honey-like fluid from
the
Newcomer's gland on it's back. After a while the larva taps its
posterior segments against the ground, sending a vibratory signal to
the ant. The ant then wanders
off but returns later with other ants to further "milk" the larva.
After several milking sessions the
larva becomes immobile and hunches it's back. This allows the
ant to seize it and carry it into the brood chamber of the ant nest.
Once settled in its new home the larva becomes carnivorous, feeding on tiny ant grubs.
Only the
largest ant nests produce the 1500 or so grubs that are
necessary for the Large Blue larva to complete its growth.
The larva is tolerated and protected by the adult ants in
exchange for providing them with a regular supply of "honey"
from it's dorsal gland. It also emits
pheromones and produces sounds that have been shown to appease the ants and assure its safety.
The
arion larvae spend several weeks in the
ant nest, feeding exclusively on ant grubs until they pupate.
In Africa the larvae of
Lepidochrysops have a similar
association with Camponotus ants.
Another Lycaenid species
Euliphyra
hewitsoni lives in the nests of
Oecophylla
tailor-ants, also feeding on a diet of ant grubs. Its cousin the
Woolly Leg butterfly
Lachnocnema
lays its eggs amidst colonies of psyllid
or
membracid bugs. The resulting larvae feed carnivorously throughout their
lives, attacking and devouring the tiny insects.
In Borneo,
Allotinus
apries
feeds on coccids when it is small. As it grows bigger the larva develops
protrusions on its body. These protrusions are used as grapples by an ant called
Myrmecaria lutea which carries the larva to it's nest.
Thereafter the larva lives within the nest, feeding on ant grubs.
The
extraordinary caterpillar of
Liphyra brassolis lives inside the nests of weaver ants
Oecophylla smaragdina, devouring hundreds of ant grubs.
A single nest can house as many as 5 or 6 Liphyra
larvae. Any other larva
that found it's way into an ant nest would
be killed, but the tortoise-like Liphyra
larva has a built-in survival kit in the form of a tough chitinous carapace that is impervious to ant bites. The ants
repeatedly attempt to flip it over to reach the soft under-belly, but the
larva uses it's powerful sucker-like feet to
pull the carapace down and seal it limpet-fashion against the substrate,
defeating all attempts by the ants to gain entry. Periodically the larva lifts the carapace slightly and pops
it's head out to snatch an ant grub with its mandibles. In an instant
the grub is pulled under the carapace. The larva then pierces the
skin of the grub, and sucks out the juices. The grub's empty skin is then ejected, and the killer larva moves on to find its next
victim.
The pupa of Liphyra brassolis is
formed within the ant nest.
The ants don't attack the pupa as it is able to
mollify them by using chemical deterrents, and by stridulating. Research on
Lycaenids has
demonstrated that the larvae and pupae of at least 150 species
worldwide are able to generate a "melody" of audible
chirps that appease ants.
Liphyra brassolis larva, Siem
Reap, Cambodia
© Dani Jump
By associating with
ants, Lycaenid larvae gain protection from other small predatory
insects which avoid ants in case they are attacked. For the same
reason larvae are less likely to be attacked by parasitoids - one
study found for example that ant-attended larvae of
Glaucopsyche suffer much lower levels
of parasitism by Braconid wasps and Tachinid flies compared with
unattended larvae.
All documented
Lycaenid larvae have one or more adaptations specialised for
association with ants. They include the dorsal Newcomers organ which
lies between the 7th/8th abdominal segments; and a pair of eversible
tentacles either side of it. These secrete a substance similar to
aphid honeydew, which acts as an ant-attractant. The substance
contains glucose, sucrose, fructose and amino acids including
serine, histidine, glutamic acid, lysine and arganine. The variable
proportions of the amino acids gives the secretion of each species a
distinctive "signature" which ensures that it attracts the correct
species of ant.
Another adaptation
of Lycaenid larvae is the presence of epidermal glands ( pore
cupolas ) which exude substances that appease the normally
aggressive ants. In combination these adaptations allow the larvae
to manipulate the behaviour of ants for their own benefit.
Species that have
dependent, mutually beneficial or
symbiotic relationships with ants are known as myrmecophiles. The
act of feeding on ants is called
myrmecophagy. The
act of feeding on aphids or other homopteran bugs is called
aphytophagy.
The evolution of
myrmecophagy and aphytophagy
Myrmecophagy and
aphytophagy probably have their origins in long-term exposure to ant-attended homopterans.
The following hypothetical example might illustrate how such
behaviours evolved:
The larva of the Purple Hairstreak Quercusia
quercus feeds on oak leaves. Ants forage on oaks to obtain
honeydew, which they milk from aphids and from
Quercusia larvae. It is feasible that ants might at some stage
in the future acquire the habit of carrying submissive
quercusia larvae to their nests. There
the larva might feed on substances regurgitated by ants, which are
chemically similar to the oak sap that aphids convert into honeydew.
Ants feed their grubs on these regurgitations, so the flesh of the
grubs probably has a taste similar to oak leaves. A hungry
Quercusia larva, which like most other
Lycaenidae has cannibalistic tendencies, would soon start nibbling
at objects in the ant nest, and it would not be long before it
started to eat ant grubs.
In order for larvae
to be able to co-exist with ants they had to evolve ways to protect
themselves from attack. Lycaenid larvae for example have
skin that is about 5 times thicker than that of those in other
families of Lepidoptera, and is thus more resistant to ant bites.
Another adaptation is the evolution of tough fleshy lappets
along the lower edge of the caterpillar's abdomen. These enable it
to seal its body against the substrate, making it harder for an ant
to flip it over to reach the soft underbelly.
Ants have acute eyesight and tend to run towards moving objects, so
Lycaenid larvae make themselves less obvious by adopting a slow
gliding form of locomotion.
Lycaenid larval
feeding
The
table below lists the larval feeding behaviour of several genera of
Lycaenidae. The genera are highlighted in colour to indicate the
subfamilies Liphyrinae,
Miletinae,
Theclinae & Polyommatinae.
Larvae of Lipteninae,
Poritiinae and Lycaeninae feed exclusively on plants. The Curetinae
require further investigation - their larvae are plant-feeders
and are attended by ants although there is no evidence yet of
ants milking them. The Riodinidae, which some workers consider to be a
subfamily of Lycaenidae, includes many species that are suspected of
being
carnivorous or aphytophagous.
|
Genus |
larval behaviour |
|
Euliphyra |
larvae solicit and receive
regurgitations from ants |
|
Liphyra |
young larvae feed on ant
regurgitations, older larvae eat ant grubs |
|
Aslauga |
older larvae predatory on
membracids, coccids and psyllids |
|
Miletus |
live in ant-attended homopteran
colonies, predatory on aphids and coccids |
|
Allotinus |
predatory on aphids |
|
Megalopalpus |
eggs laid on membracid nymphs |
|
Taraka |
imbibe honeydew, and predatory
on aphids |
|
Spalgis |
predatory on coccids |
|
Feniseca |
predatory on woolly aphids |
|
Lachnocnema |
predatory on jassids,
membracids and psyllids |
|
Thestor |
larvae scavenge on secretions
and excrement of coccids |
|
Acrodipsas |
early instars feed on ant
regurgitations, older instars devour ant grubs |
|
Shirozua |
early instars imbibe honeydew,
older instars devour aphids |
|
Zesius |
cannibalistic on own species |
|
Spindasis |
early instars feed on leaves,
older instars on Crematogaster ant regurgitations |
|
Jalmenus |
live in ant nests, suspected of
feeding on ant grubs |
|
Oxychaeta |
live in ant nests, suspected of
feeding on ant grubs |
|
Trimenia |
suspected to feed on honeydew
and/or aphids |
|
Argyroplaga |
suspected to feed on honeydew and/or aphids |
|
Triclema |
predatory on coccids |
|
Lysandra |
all instars on foliage, older
larvae milked by ants, pupae ant-attended |
|
Niphanda |
early instars on aphid
excretions, older larvae on ant regurgitations |
|
Maculinea |
early instars on flowers,
aggressively cannibalistic, older larvae on ant grubs |
|
Lepidochrysops |
early instars on flowers, aggressively cannibalistic, older
larvae on ant grubs |
|
Plebejus |
early instars on flowers and
leaves, older larvae milked by ants |
More odd feeding habits
The moth
Ceratophaga vicinella
lays it's eggs on the empty shells of dead Florida Gopher
Tortoises Gopherus polyphemus.
The resulting larvae feed gregariously on the keratin shells,
constructing a mass of silk tubes which act as anchors, connecting
the outer shell to the sandy substrate.
Many moths have larvae that feed on
dung. These include Acrolophus pholetus
and Idia gopheri,
which both spend their lives feeding on dung within the burrows of
the Florida Gopher Tortoise.
In Africa, the caterpillars
of other Ceratophaga
species feed in tunnels within the hooves and horns of antelopes and
cattle. Ceratophaga
species are members of the Tineidae - the family to which clothes
moths belong. The larvae of the Case-bearing Clothes moth
Tinea pellionella
are notorious for their habit of eating holes in woollen fabrics
but in the wild state live within bird's nests, feeding on the
keratin in hairs and feathers. The larvae of the related Tapestry moth
Trichophaga tapetzella
feed on coarser fibres, and are also common
in owl pellets ( regurgitated fur and bone ).
5 -
Larval survival mechanisms, armature, camouflage, disguise >>>
|
