Butterflies of the World - Lifecycle, Ecology, Taxonomy, Conservation, Photography, Butterfly Holidays, Photo Galleries, Book Reviews and more.........
Text and photographs protected by Copyright © Adrian Hoskins 2007, and must not be published in part or in whole elsewhere without prior written permission from the author.
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  NEXT >> ( more fascinating caterpillars )
 
hatching | feeding | carnivores | cannibals | anatomy | moulting | armature
 
Caterpillar of Privet Hawkmoth Sphinx ligustri ( Sphingidae ), Hampshire, England.
 
Caterpillar of Purple Hairstreak Quercusia quercus ( Lycaenidae ) feeding on oak.

Hatching

Most butterfly eggs undergo colour changes as the young caterpillars develop within them. The eggs of the Marsh Fritillary Euphydryas aurinia for example are pale yellow when first laid, but after a day or two turn pinkish-brown, then deep crimson, and finally dark grey just before the caterpillars hatch.

When a caterpillar is ready to hatch, it bites a tiny hole out of the top of the egg, and over a period of an hour or so, nibbles away until the hole is large enough to allow it to crawl out. Some species use a different technique, nibbling a circle around the perimeter of the egg to create a "lid" which is pushed upwards to allow the caterpillar to make it's exit.
After hatching, some caterpillars such as that of the White-letter Hairstreak Satyrium
w-album rush immediately away and eat their way into a young leaf bud or flower. Most caterpillars however stay long enough to devour most of their eggshell, which contains vital nutrients, and will die if prevented from doing so.
 
Larva of Lackey moth Malacosoma neustria, ( Lasiocampidae ) Oxfordshire, England.

Feeding

For the remainder of the larval stage they feed on the leaves, stems, flowers or seeds of particular plants. Some species are adapted to feed on a variety of different plants, but most are limited to just one or two plant species, and will refuse to eat alternatives.

Very young larvae such as this 1st instar Buff Ermine Spilosoma luteum feed by nibbling tiny holes in the lower cuticle of leaves. At this stage the larva is about 3mm in length and feeding on privet.
 
By the time the Buff Ermine larva is fully grown it has changed colour, grown a thick coat of hair, and changed to a different foodplant. This individual is in it's 5th instar, feeding on bramble.

Larvae and adult butterflies of any given species generally use different sources of food. Marsh Fritillary caterpillars for example eat the leaves of devil's bit scabious, but the adult butterflies feed on the nectar of buttercups, milkworts and thistles. In temperate areas the larvae and adults live at different seasons, but in the tropics, where the 2 stages often co-exist at the same time of year, the dichotomy between larval and adult feeding behaviour enables them to avoid competing for food.
Caterpillars often feed on different parts of their foodplant at different stages in their growth. The young larvae of the Purple Hairstreak Quercusia quercus hatch before the leaves appear on oak trees, so at first they burrow into the leaf buds to feed. Later, they feed on the foliage. They make a "nest" by spinning a thin web of silk around a clump of leaves, resting within it by day, and emerging at night to feed.
 
 
Leaf-miners
The newly hatched caterpillars of some moths, known as "leaf-miners" burrow into leaves and spend their entire lives living and feeding between the upper and lower membranes.  Each species leaves it's own characteristic trail as it weaves it's way about between the membranes. When the caterpillar is fully grown it emerges and pupates on the surface of the leaf.
Leaf-mines produced by caterpillars of the moth Stigmella aurella
 
 
 
Not all caterpillars feed on living flowers or leaves.  Some, including the Groundstreaks Calycopis ( Lycaenidae ) and Detritus Metalmarks Detritivora ( Riodinidae ) feed on dead vegetation on the forest floor. Others, such as those of the Goat moth Cossus cossus
( Cossidae ) live within tunnels in the trunks of dying trees, chewing their way through solid wood !
 
The duration of the larval stage varies according to the the nutritional value of the food. Species which eat foods with high nutritional value ( flowers, fruits ) grow quickly, going from egg to pupa in less than a month. Species which feed on leaves take longer, up to 2 months, because leaves are harder to digest, and often contain toxins which need to be processed.
 
Slower still are the species which feed on grasses, bamboos, palms or plant roots, all of which are low in nutrients and particularly difficult to digest. In these species the larval stage usually lasts at least 3 months. In the case of species from temperate regions growth is often so slow that the larvae are unable to complete their development during the summer, and have to hibernate and resume feeding the following spring.
 
Cannibals and carnivores
 
Not all caterpillars feed on exclusively on vegetation. Some species such as the Orange tip butterfly Anthocharis cardamines ( Pieridae ) and the Dun-bar moth Cosmia trapezina ( Noctuidae ) have strong cannibalistic tendencies. Both normally eat living vegetation but will attack and eat any other larva that they encounter.
 
Cannibalism has two possible advantages for larvae - firstly by eradicating competitors they ensure they have enough leaves for themselves. Secondly, they grow faster because they save themselves the time-consuming business of digesting and processing the vegetation. There is also unpublished evidence ( Hoskins ) that Orange tip larvae which are deprived of the opportunity of cannibalism produce smaller and weaker adult butterflies. It is perhaps surprising that cannibalism is not more prevalent.
 
Caterpillars of the Large Blue Maculinea arion, feed in their early instars on flowers or leaves. When older they produce and disseminate pheromones similar to those of the ant Myrmica sabuleti. The ants, which under other circumstances would probably kill and eat the caterpillars, are appeased by the pheromones, and fooled into carrying them back to their underground nests, where they feed on the ant grubs.
 
In Africa, caterpillars of Euliphyra hewitsoni ( Miletinae ), live in the nests of Oecophylla tailor-ants, feeding on ant grubs. Their cousins, the Woolly Leg butterflies Lachnocnena, and Harvester butterflies Megalopalpus lay their eggs amidst colonies of aphids, coccids, psyllids or membracids ( Homoptera ), and their caterpillars feed throughout their lives by attacking and consuming the living insects.
 
In Borneo, another member of the Miletinae, Allotinus apries, feeds on coccids when it is tiny, but during the 2nd instar the larva develops protrusions which act as grapples used by a particular species of ant Myrmecaria lutea, to carry it to it's nest - where the larva proceeds to devour the ant grubs.
 
More odd feeding habits
 
Another fascinating species* is the moth Ceratophaga vicinella, which lays it's eggs on the empty shells of dead Florida Gopher Tortoises Gopherus polyphemus. The resulting caterpillars feed gregariously on the keratin shells, constructing a mass of silk tubes which act as anchors, connecting the outer shell to the sandy substrate. In Africa, the caterpillars of other Ceratophaga species feed in tunnels within the hooves and horns of antelopes and cattle.
 
* Source : "Of Moths and Tortoises" by Don Stillwaugh, Newsletter of the Gopher Tortoise Council, Vol 26.
 
Ceratophaga species are members of the Tineidae - the family to which clothes moths belong. The caterpillars of the Case-bearing Clothes moth Tinea pellionella are well known 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 caterpillars of the related Tapestry moth Trichophaga tapetzella feed on coarser fibres, particularly horse hair, and are also common in owl pellets ( regurgitated fur and bone ).
 
Many moths have caterpillars that feed on dung. These include two species Acrolophus pholetus and Idia gopheri, which both ( as you may have guessed from the scientific name of the latter ) spend their lives feeding on dung within the burrows of our friend the Florida Gopher Tortoise !

Anatomy
larva of Broad-bordered Yellow Underwing moth Noctua fimbriata ( Noctuidae )

A caterpillar has only 2 functions during it's life - to eat, and to survive.

It is basically just an eating machine, with large powerful jaws ( mandibles ), a huge gut, legs to enable it to move around it's foodplant, small eyes, and a segmented and highly elastic skin which stretches to accommodate the huge amount of food consumed.

All butterfly caterpillars have six true legs located on the first 3 ( thoracic ) segments, which are used primarily for holding and manipulating the leaves on which they feed. On the abdominal segments they have 4 pairs of false legs called "prolegs" - effectively suckers that enable them to cling to stems or leaves, and to walk. There are also a pair of gripping "anal claspers" at the tail end of the body, which are used to secure the caterpillar while the prolegs are doing the walking.

The caterpillars of many butterflies and moths spin a sticky silken trail as they walk, which enables them to grip the stems and leaves more securely. If they lose their grip, most larvae fall to the ground and are unable to find their way back again, but the larvae of some moths spin a silk "bungee cord" from which they dangle if jolted from their foodplant, and are able to use it to pull themselves back up.

Moulting

As the larva feeds and grows, it's elasticated skin eventually becomes too tight, and has to be moulted. Moulting is triggered by nerve cells called scolopidia, which detect stretch in the elastic skin between the caterpillar's segments.

Each of the stages between moults is known as an instar. Caterpillars of the Lycaenidae have 4 instars, but those of the Hesperiidae, Nymphalidae, Papilionidae and Pieridae have 5 instars. The Riodinidae have between 6 - 8 larval instars according to species.

Prior to moulting, caterpillars anchor themselves either to a small pad of silk that they have spun on a leaf or twig; or to a silk web spun over the foodplant. Many species live communally in such webs, and usually moult in synchrony with their fellows.

A few days before a larva is due to moult, a loose baggy elastic second skin forms under the outer skin. At the same time, the soft tissues within the head retract, forming a new head which is temporarily housed within the first thoracic segment. The old head shell slides forward until it eventually drops off, and the "old" skin splits just behind the head, allowing the caterpillar to walk forward out of its former costume.

At first the new skin is loose and soft, leaving the larva highly vulnerable to attack by parasitoid wasps and flies. The larva slowly inflates it's body by drawing in air through the spiracles, and then waits for the skin to harden. After a couple of hours it has usually hardened enough to allow the larva to walk about without injuring itself, and feeding recommences.

The caterpillars of Peacock, Small Tortoiseshell and Marsh Fritillary butterflies, and those of many moths, spend most of their lives feeding communally within substantial silk webs where they are protected from predators, parasitoids and severe weather. These species tend to moult synchronously, after which they move as a group to another clump of foliage where they spin another web.
 
The communal web of the Small Eggar caterpillar ( Lasiocampidae )

With each successive moult, the larva 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 older larvae become darker, or browner, to match the colour of older 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.

 
Related subjects :
 
Anatomy - the structure and biology of adult butterflies.
Parasitoids and Predators - of eggs, larvae, pupae and adult butterflies.
 
Courtship rituals and many other aspects of adult behaviour are discussed in detail in the individual species accounts, which can be accessed from the Species Index, or by clicking on thumbnail images of butterflies in the Photo Galleries.
 
 
Text and photographs protected by Copyright © Adrian Hoskins 2007-2008, and must not be reproduced or published in part or in whole elsewhere in any form without written permission from Adrian Hoskins. Breach of copyright will be pursued by litigation.
 
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