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 ) 
Ovum  NEXT >> ( caterpillars )
anatomy | fertilisation | oviposition | incubation
The shape, size, colour and texture of butterfly eggs varies enormously from one species to another. Those of Satyrines and Heliconiines are typically domed or barrel-shaped, adorned with between 8-30 vertical ribs, between which can be seen dozens of lateral ridges. Other butterflies, including most Hesperiidae, Papilionidae and Riodinidae, produce smooth globular eggs. Those of the Polyommatinae ( Blues ) have a finely reticulated surface, and are shaped like flattened do-nuts. Pierines ( Whites and Sulphurs ) produce eggs which are tall and skittle-shaped, with fine vertical ribbing.
All butterfly and moth eggs have a depression at the top, in the centre of which is a hole known as a micropyle, through which sperm enters during fertilisation. The egg shell is peppered with thousands of microscopic pores, through which air enters to sustain the developing larva within.
Thecla betulae egg details


In the case of Nymphalidae ( and probably other butterflies ) the eggs are already formed within the body of females when they emerge. They grow in size over a period of 2 or 3 days, as they mature within the female's abdomen. Egg-laying is triggered when they reach a certain size, at which time they pass from the ovariole to the egg chamber. They are fertilised just prior to egg-laying, the male's sperm having been stored until this time within a receptacle in the female abdomen.


Butterflies lay their eggs either singly or in batches, on or near the foodplants that will be used by the caterpillars.


Some species, e.g. the Marbled White Melanargia galathea, drop their eggs randomly as they fly amongst tall grasses, but most species have very precise requirements. Pearl-bordered Fritillaries Clossiana euphrosyne for example lays their eggs singly on dead bracken or dry grass stems that are within a metre of their caterpillar's foodplant, dog violet. The White-letter Hairstreak Satyrium w-album is even fussier, always laying it's eggs on elm twigs, at the precise point where the new year's growth and old growth meet.


Silver-washed Fritillaries Argynnis paphia lay their eggs in chinks on the bark of oak trees, but the larvae don't eat oak - they begin by eating their own egg-shells, and then go into hibernation until the following spring, when they descend the tree trunks to feed on the leaves of nearby violets.

Orange tip caterpillars Anthocharis cardamines normally feed on cuckoo flower or garlic mustard leaves, but if they encounter another caterpillar they become cannibalistic. It would therefore be wasteful if the butterflies laid more than one egg on each plant, so nature has endowed the females with the ability to detect eggs that have already been laid, and thus avoid laying more than one egg per plant.


In the tropics, eggs are often glued underneath the leaves of trees and bushes, where they are protected from rain, and from the desiccating effects of hot sunshine. In the Amazonian rainforests Heliconiine butterflies often lay their eggs on Passiflora tendrils, presumably to place them as far out of the reach of marauding ants as possible.

Foodplant selection

The caterpillars of most species will only eat the leaves of one or two species of plant, and will die if they find themselves on the wrong type of tree, bush or herb.


Butterflies therefore spend a great deal of time "tasting" foliage, using olfactory sensors on their feet, abdomens and antennae to determine whether the plant is of the right species for egg-laying. All female butterflies have spines on the underside of their forelegs. When they land on a leaf these spines puncture the surface, releasing aromas that are detected by the olfactory sensors.
In Peru I watched a female Methona confusa which spent half an hour flitting around a particular nightshade plant ( Solanaceae ). She momentarily settled and tasted at least 20 individual leaves, several of which were revisited many times, before finally settling to lay a single egg.

From this it can be seen that it is not just enough to locate the correct species of plant. The eggs usually have to be laid on tender young leaves or buds, as the older leaves often contain toxins that can kill them. They also have to be laid on plants that are growing in very precise conditions - just the right degree of shade, just the right conditions of temperature and humidity, and at a height on the plants where they will not get eaten by browsing herbivores. Eggs are often laid on the tips of buds, usually quite high up on the tree or bush. This way they are less likely to be found by ants.

Laying in batches

egg batch under leaf, species unknown, Peru

The caterpillars of most butterflies live solitarily, but some, particularly amongst the Melitaeini, Morphini and Pierini, live gregariously for the majority of their lives. The females of these species lay their eggs in batches, sometimes as many as 500 at a time. The Marsh Fritillary Euphydryas aurinia is a typical example - it lays about 300 eggs in a single batch, on the underside of a leaf of devil's bit scabious, always within a few metres of the spot where the female emerged from it's pupa. Having laid most of it's eggs the female then disperses and sometimes lays another much smaller batch of eggs slightly further afield.

egg batch of Marsh Fritillary Euphydryas aurinia, Wiltshire, England


The incubation period varies greatly from species to species. Eggs of tropical butterflies usually hatch within a week, but in temperate areas 10-14 days is more typical. There are however many species, such as Purple Hairstreak Quercusia quercus, Chalkhill Blue Lysandra coridon and High Brown Fritillary Argynnis adippe, in which the eggs hibernate over winter, and in these cases the incubation period can last for several months.

Natural enemies

The eggs of butterflies and moths are valuable sources of protein, and prone to predation by snails, slugs, and various bugs and beetles. They are also eaten accidentally by mammalian herbivores.
It may seem surprising that something as small as a butterfly egg has its own parasitoids, but these cause high losses. The main parasitoids are wasps in the families Scelionidae and Trichogrammidae - as many as 60 of these microscopic wasps can emerge from a single butterfly egg !
NEXT >> ( caterpillars )


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