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| Within
a week after the female lays her eggs they begin to hatch. The newly
hatched larvae are very small and difficult to see. The first thing
we noticed were little holes in the Fast Plant leaves where the larvae had
been munching. Upon closer inspection we could see the tiny
caterpillars. |
Newly
Hatched Larvae
magnified
10 X
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After
hatching, the larvae grow very quickly. As soon as they grow too big
for their skin they molt (shed) their old skin for new new skin underneath
that fits them better. These larval growth stages are called instars.
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Pieris
rapae goes through 5 instars before
transforming into a chrysalis.
Photo: M. Keller, Adelaide University |
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| The
Brassica Barn, a simple yet very efficient feeding system, consists of an
ordinary film can filled with sand. Four toothpicks are inserted
into the sides of the film can supporting halved Brussels sprouts on which
the larvae feed. The little specks you see on the bottom of the
Brassica Barn are larval excrement called frass. |
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Brassica
Barn |
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| It
is easy to tell the male larvae from the female larvae once they are
mature. The males have two small dark parallel lines on their backs
as seen in this photo, and the female larvae do not. |
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Mature Brassica Butterfly Larvae
digital photo close-up |
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If
left to feed on the Wisconsin Fast Plants from hatching to pupating, these
"hungry, hungry, caterpillars" will eat every leaf they
find. They are not a bit shy about munching on seed pods and plant
stalks if they can't find any leaves. It is very easy for us to see
why farmers consider this butterfly a pest.
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Larvae-Damaged
Wisconsin Fast Plants
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