The butterfly lifecycle
1 - Egg
- anatomy, oviposition
2 - Caterpillar
- hatching, feeding and development
- cannibals, carnivores and myrmecophiles
- survival mechanisms,
armature, camouflage / disguise
co-evolution with plants
- pupation, metamorphosis
- emergence, feeding
- mate location and courtship
10 - Adult
- daily routine, roosting, hibernation, lifespan
: hatching, feeding & development
Most butterfly eggs undergo colour changes as the young larvae 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 larvae hatch.
The eggs of the Orange tip Anthocharis
cardamines are pure white when first laid, but turn orange
within 2-3 days, then become dull grey when hatching is imminent.
Anthocharis cardamines - the egg on the
right is freshly laid
© Adrian Hoskins
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
After hatching, some caterpillars such
as that of the White-letter Hairstreak
w-album rush immediately away and eat their way into a young
leaf bud or flower. Most larvae however stay long enough to partly
devour their eggshell, which contains vital nutrients. If deprived
of the opportunity to eat the eggshell caterpillars usually die.
For the remainder of the
larval stage most species feed on the leaves, stems, flowers or seeds
of particular plants. Some species are polyphagous, i.e. they are
adapted to feed on a wide variety of plants from different botanical
families. Most however are monophagous, i.e. limited to feeding on
just one or two closely related plant species, and unable to survive
on anything else. Many species in the family Lycaenidae are
carnivorous, feeding on ant grubs or aphids. This group is dealt with
in detail on the
cannibals, carnivores and myrmecophiles
instar Spilosoma luteum larva nibbling
tiny holes in the lower cuticle of leaf ©
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 the 2 stages
often co-exist at the same time of year, so the dichotomy between
larval and adult feeding behaviour enables them to avoid competing for
make up of plants changes seasonally. Plants often accumulate toxins
in their leaves as a means of defence against caterpillars. Older
leaves are more strongly toxic and have less protein than younger
leaves. Towards the end of the season leaves may be so toxic that they
can kill any caterpillar that eats them. Therefore the larval stage of
many species, particularly oak feeders, tends to be compressed into
the early part of the season.
which breed on less nutritional plants need to spend several months in
the larval stage, so towards the end of the season they need to search
out the freshest and least toxic leaves if they are to survive. Some
species even switch to alternative host plants which come into leaf
later in the year.
Caterpillars often feed on different parts of their foodplant at
different stages in their growth.
The balance of
proteins, carbohydrates, minerals, alkaloids and essential oils in
plant leaves varies considerably at different times of day.
Caterpillars therefore tend to be feed at specific times when the
foliage is most nutritional and least toxic. Some species therefore
feed at dawn, others in mid-afternoon, and others at night.
further reasons why many caterpillars only feed nocturnally. Firstly
they are less likely to be preyed upon by insectivorous birds, which
need daylight in order to locate their prey. Secondly, larvae of
Satyrinae and Hesperiinae which feed on grasses - and species which
feed on herbaceous plants - are prone to be accidentally consumed by
diurnal grazing animals such as rabbits, sheep or cattle. To avoid
this they evolved to become nocturnal feeders, and in the daytime hide
away deep down in grass tussocks where grazing animals can't reach
The duration of the
larval stage varies according to 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 up to 2 months. This is 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 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.
Depending on the species, caterpillars
increase their body weight between about 60-200x in the period between
hatching and pupating. Accordingly as
it feeds and grows, a caterpillar's elasticated skin periodically
becomes too tight and has to be moulted and replaced with a looser
baggy elastic second skin that forms under the outer skin.
Moulting is triggered by
nerve cells called scolopidia, which detect stretch in the skin
between the caterpillar's segments.
Two or three days before moulting caterpillars
anchor themselves either to a small button of silk which they have
spun on a leaf or twig; or to a silk web spun over the foodplant.
A day or two prior to
moulting the soft tissues within the caterpillar's head retract,
forming a new head capsule which is temporarily housed within the
first thoracic segment. When moulting takes place the old head shell
slides forward and drops off. The old skin then splits just behind the
head, allowing the caterpillar to walk forward out of its former
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. After a couple of hours the
larva's mandibles ( jaws ) have hardened, at which point a larva will
often eat it's old skin. Another 2 hours or so later the skin has
toughened sufficiently to allow the larva to walk about without
injuring itself, and to resume normal feeding.
The stages between moults are known as
instars. Caterpillars of the family Lycaenidae usually have 4 instars.
Those of the Hesperiidae, Nymphalidae, Papilionidae and Pieridae
usually have 5 instars. The Riodinidae have between 6-8 larval instars
according to species.
The newly hatched larvae 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 larva 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. Calycopis
for example feed on dead vegetation on the forest floor, while some
moths such as
live within tunnels
in the trunks of dying trees, chewing their way through solid wood.
Larval webs and
The caterpillars of many
butterflies including Peacock, Small Tortoiseshell and Marsh
Fritillary live gregariously. They spend most of their lives within
substantial silk webs. They emerge periodically to feed, but then
retire to the silken shelter 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.
web of the Small Eggar caterpillar ( Lasiocampidae ) ©
Many other species live solitarily and construct individual shelters
or tents in which they hide while resting. These include skipper
butterflies ( Hesperiidae ), Pyralid moths ( Pyralidae ) and
Charaxine butterflies in the genera Memphis
and Consul. The latter hide in rolled
leaves and plug the entrance with their head capsule. This is
sclerotised and too hard to be pierced by the ovipositor of
parasitoid wasps. Other parasitoids such as Tachinid flies cannot
gain access to lay eggs on the larva's body, and the secrecy
provided by hiding in the shelter also undoubtedly confers a degree
of protection from birds and other foraging predators.
Case-bearing larva of bagworm moth
Psyche casta ( Psychidae ) Berkshire, UK ©
Some of the most primitive and
interesting larvae are those of the case-bearers ( Coleophoridae )
and bagworm moths ( Psychidae ). These species provide part of the
evidence that links butterflies and moths ( Lepidoptera ) to the
insects from which they evolved, i.e. caddisflies ( Trichoptera ).
In common with caddis larvae, the
caterpillars of Coleophoridae and Psychidae construct shelters or
bags made from silk and natural materials such as dead leaves, bits
of wood, lichens or grains of sand. The cases have a tubular exit
hole at the front end, and a small hole at the rear from where
excrement is ejected. The larvae never leave their cases, so as they
grow they have to continually add more material to the front of the
case to accommodate their increasing size.
When moving from place to place the
larvae anchor themselves to the inside of the case with their anal
claspers, and extend the front of their bodies out of the case, just
far enough to allow them to grab hold of the substrate with their 3
pairs of true legs to haul themselves along.
The larvae within the cases are all
very plain creatures, so it is usually easier to identify a bagworm
or case-bearer from the design of the case, which is different for
every species. The cases measure from about 1cm in the smaller
temperate species, up to 15cms in some tropical species.
When the caterpillar is fully grown
it secures the case to a twig or branch, and pupation takes place
within the case. Male moths are winged, but females of most species
are wingless and usually don't possess antennae, eyes or legs.
Females never leave their larval case. When copulating the male
reaches into the case with his abdomen to make sexual contact. The
female lays her eggs inside the case and then dies.
The female of one species, the
Evergreen bagworm Thyridopteryx
ephemeraeformis dies without laying eggs. Its tiny
caterpillars emerge direct from the female body inside the case.
Some species are parthenogenetic, i.e. their eggs develop without
Larva of unidentified bagworm moth,
Bobiri, Ghana ©
As larvae grow and mature they begin to develop sexual organs
internally, but it is not possible to determine the sex of a larva
from its external appearance. There are however some species of
Lepidoptera in which
that will ultimately become males have 4 instars, while those that
will become females have 5 instars.
An example is the Vapourer moth Orgyia antiqua
in which the female larvae grow to a much larger size than the
males. The male moth looks much like any other moth, but the female
is wingless and has an enormous abdomen swollen with hundreds of
In tropical regions larvae can
develop very rapidly, and in some species the entire larval period
may be as short as 2 weeks. In temperate regions the larval stage
usually lasts about 6 weeks, but is often much longer. Many species
particularly amongst the Satyrinae overwinter as larvae, taking
several months to mature. There are even a few sub-Arctic species in
which the larval stage can last for 2 years.