Peacock (Early Stages)

Transcription

01 February 2014
© Vince Massimo
Citation: Massimo, V. (2014). Peacock (Early Stages) [Online]. Available from http://www.dispar.org/reference.php?id=27 [Accessed February 1, 2014].
Peacock (Early Stages)
Vince Massimo
Eggs and Larvae
The Peacock is an iconic butterfly and its larvae are quite easy to find, but not many people have seen a Peacock pupa or can distinguish
one from a Small Tortoiseshell.
Eggs are laid in batches of 300-500 on the undersides of Common Nettle leaves, but unless you actually observe them being laid, they are
quite difficult to find. The jade-green barrel-shaped eggs are laid in a compact mound, often piled 2 or 3 deep, which can take the female
over an hour.
Female Peacock egg laying
Coulsdon, Surrey 19-May-2013
Photo © Vince Massimo
Female Peacock egg laying
Peacock ova
Female Peacock (resting after egg
laying)
Peacock eggs (1 day before hatching)
Coulsdon, Surrey 14-June-2013
Peacock eggs hatching
1 of 9
Peacock eggs hatching
Peacock larvae emerging
Upon hatching the young larvae spin a dense web of silk over the leaf and when this is consumed do the same thing at the growing tip of
the plant, where they feed and rest communally. Safety in numbers is a defence strategy for this species, but living as a group also enables
them to raise their body temperature above ambient levels, which means that they can remain active even in cooler conditions. They also
need these higher temperatures in order to digest their food more efficiently.
Larval webs are easy to spot in June and early July and they seemed to be particularly abundant this year (2012) when I found 15 on
sunny, sheltered nettle beds at a local site.
Peacock (1st instar web)
Peacock (1st instar web)
Peacock larvae (2nd instars)
Peacock larvae (1st and 2nd instars)
Peacock larvae (2nd instar pre-moult
group)
Caterham,Surrey 4-July-2012
As the larvae grow and moult they move to different areas of the plant or fresh plants, leaving a trail of old webs, larval skins and
droppings, making them even easier to locate. By the time they are in their 3rd instar they have acquired their full silky-black colouration
with white spots, long dark spines and pale legs.
2 of 9
Peacock (3rd instar larval web)
Coulsdon, Surrey 15-July-2012
Peacock larva (3rd instar)
Caterham, Surrey 12-July-2012
Peacock larvae (3rd and 4th instars)
When ready to pupate a larva will usually leave the plant and spins a pad of silk on a stem or branch. Here it attaches itself, hanging
head-down in the characteristic pre-pupation "J" shape for a day or two.
Peacock larva (spinning a silk pad)
Peacock larva (awaiting pupation)
Just prior to pupation the larva straightens slightly and starts to pulsate its body. The skin also begins to look baggy, before suddenly
splitting behind the head and gradually being sloughed off. This process appears particularly dramatic in this species because of the
difference in colour between the old skin and the new pupa, which only serves to accentuate the variance in size between the two stages.
3 of 9
Peacock larva (preparing to pupate)
Caterham, Surrey 16-July 2012
Peacock larva (commencing pupation)
Peacock larva (pupating)
Peacock larva (completing pupation)
Peacock pupa (freshly emerged)
The Pupa
Peacock pupae come in two different colour forms depending on their environment. The blackish/grey form tends to be found in such places
as dark tree trunks and fences, while the yellow/gold variety is usually located beneath leaves. All of mine pupated on nettle stems and
twigs and were of the yellow variety.
4 of 9
Peacock pupa (freshly emerged)
Peacock pupa (30 minutes old)
Peacock pupa (7 hours old)
Peacock pupa (1 week old)
They are similar in appearance to those of the Small Tortoiseshell, which also have "Horns and Thorns", but with subtle differences.
Peacock pupa (showing Horns and
Thorns)
Peacock pupa (showing Horns and
Thorns)
5 of 9
There are colour changes in the wing area of there pupal case approximately 36 hours before hatching. These colours continue to darken
and spread, with the abdominal area being the last to be affected.
Peacock pupae (showing different
colour changes)
Peacock pupa (36 hours before
hatching)
hatching)
hatching)
A few hours before hatching takes place the pupa takes on a markedly paler appearance as the wings and body of the adult break contact
with the inner face of the pupal casing. The abdominal segments also distend as the butterfly draws in air through tubes linked to the
spiracle openings in the sides of the pupa and starts to pump up its body, putting pressure on the pupal case.
6 of 9
Peacock pupa (1 hour 30 minutes before hatching)
The Hatching Sequence
The increased pressure on the pupal case causes it to split on either side of the position of the head.
Peacock pupa (25 minutes before
hatching)
Caterham, Surrey 31-July 2012
Peacock pupa (commencing hatching)
Peacock hatching
Peacock hatching
Peacock hatching
Peacock hatching
7 of 9
Peacock hatching
Peacock (freshly hatched)
Peacock (expanding its wings)
Peacock (freshly emerged)
I collected two batches of larvae for the purposes of preparing this report. The first was a group of 7 second-instars and then 11 firstinstars 4 days later. There were three losses from the first group which were due to parasitism by Ichneumonid wasps (Phobocampe
confusa). The grubs emerged while the larvae were preparing to moult into their 4th instar and formed characteristic 5mm long egg-shaped
cocoons near the skins of their dead hosts. Interestingly, the adult wasps hatched at the same time as the butterflies from that batch. The
pupal stage lasted 10 days for the butterflies and 20 days for the wasps.
Phobocampe confusa cocoons
Phobocampe confusa (hatched cocoon)
8 of 9
Phobocampe confusa (adult parasitic
wasp)
All the adult butterflies were released close to their original sites while the wasps escaped while being photographed.
Reference Images of Adults
Peacock
Caterham, Surrey 1-Aug-2012
Peacock
9 of 9

Peacock (Early Stages)

Transcription

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