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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
Adult
: emergence, feeding
Emergence
Emergence of the
adult butterfly or moth from the pupa is triggered by
factors including humidity, temperature, light level and time of
day. Most butterflies emerge shortly after dawn.
The spiracles of the butterfly within the pupa are linked by short tubes to the spiracle
openings on the pupa shell. Just prior to emergence air is drawn in through these tubes,
enabling the butterfly to pump up it's body, which causes the shell
of the pupa to split, just behind the head.
The butterfly then
forces it's way out, using it's legs to pull itself clear of the
empty pupal shell. If the pupa was formed within a silken shelter
or cocoon, as is the case e.g. with most Hesperiidae species, the
butterfly first ejects solvents from the
proboscis. These soften the silk enough to allow it to push it's
way out.
Eueides lybia, newly emerged from
chrysalis, Rio Madre de Dios, Peru
Having emerged and settled into position, the
insect then
spends several minutes hanging virtually
motionless. During this time it pumps fluids into the wing veins,
causing the wings to expand to their full size.
After
drying the wings, and before taking their first flight, butterflies
and moths expel the metabolic waste product meconium from their
abdomens, in the form of a pinkish liquid. Male butterflies
usually fly off as soon as their wings are hardened, but females of
many species tend to stay within a few metres of the emergence site
until mated.
Sex ratios
It is often claimed
that more male butterflies emerge than females. The most quoted
example is of Rajah Brooke's Birdwing
Trogonoptera brookiana whose males are sometimes stated to
outnumber females by a ratio of as much as 10:1. These claims
however are caused by sampling inadequacies - females of most
species are more secretive in behaviour, better camouflaged, and
tend to spend most of their lives in habitats that are less
accessible to observers, e.g. in the forest canopy. Males on the
other hand tend to be more colourful and are considerably more
visible in their behaviour, e.g. males of
brookiana and many other species habitually aggregate in
large numbers to imbibe moisture from muddy ground. Captive breeding
experiments with brookiana and hundreds
of other species have proven that both sexes actually emerge in
similar numbers.
In most species males emerge at
least a day or two before females. The explanation usually given for this
is that females usually mate on the day they emerge, so it is
advantageous if there are already plenty of males available to them.
Another factor not usually
mentioned in literature is that males of some species are not capable
of mating until they are 2-3 days old. This is because they need to feed
in order to accumulate alkaloids that are vital to reproduction.
Well known examples of this include the
Purple Emperor
whose males feed at dung,
Swordtails and
Daggerwings
which feed at urine, and
Glasswings such as
Pteronymia sao
which feed on decomposing plant material. The latter derive
pyrrolizidine alkaloids from the plants, which are used in the
production of pheromones and defensive toxins, as well as for
reproductive purposes.
Feeding behaviour
Males of many
tropical species are regularly observed imbibing dissolved minerals from damp
mud, bird droppings, aphid secretions, sap runs, or even from
carrion. The minerals are later passed to the females during
copulation, and may contain vital nutrients necessary for the
production of fertile eggs.
In
temperate regions both sexes of most species feed primarily at
nectar, but males of several species, e.g.
Apatura iris,
Lysandra coridon,
Pyrgus alveus,
Thymelicus lineola
and
Mellicta athalia
commonly imbibe mineralised moisture, or visit dung.
Certain
members of the subfamily Heliconiinae are unusual in that their
females use nectar to dissolve pollen which they collect from
rainforest flowers. Studies by Gilbert of captive
Heliconius
ethilla in Trinidad have shown that females deprived of
pollen only lay about 15% of the number of eggs laid by females
that have access to pollen. The pollen provides nutrients that
cannot be sequestered from other sources, and contributes greatly
to the longevity of the butterflies. They have been recorded as
living for up to 8 months as adults - most other tropical species
live for only a few days.
Heliconius
erato phyllis, sequestering pollen from "hotlips" flowers
Psychotia poeppigiana
9 -
Mate location, courtship >>>
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