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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 subfamilies Lipteninae, Poritiinae and Lycaeninae have larvae
which exclusively on plants. Larvae of Curetinae 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 ).
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