Cycle of the Wall
The almost spherical shaped eggs, measuring c.0.8
mm in height, are a translucent green soon turning to white.
They are laid singly or in small clusters, on blades of grass or exposed
roots, in sheltered warm sites during
May and June and again in August. Hatching occurs in c.10 days.
In very warm summers
there may be a third brood.
The mature larva measures up to 25 mm in length. The body is
a bright bluish-green colour and has a
darker green mediodorsal line and faint white lateral lines. Below
them is a distinct pale spiracular line.
The head is green and the short anal points white.
On emergence the young larva usually eats it eggshell and thereafter
feeds on its foodplant by night although
the later instars feed also by day. There are four instars.
larvae resume feeding and growth in early spring, usually pupating from
mid to late
April, producing the first generation adults in May and June.
First generation larvae, occuring in mid-June to early August, go
on to pupate producing adults from August
to September. This larval stage lasts for c. 31 days.
Second generation larvae Overwinter
in this larval state becoming active the following spring, usually
April. This overwintering larval stage lasts c.9 months.
In mild warm summers there may be a third generation.
It has been suggested that in dry warm weather some of the summer
generation larvae may develop
rapidly enough to enter pupation and overwinter in the pupal state.
Pupation takes place on the stem of the host plant, usually
inconspicuously under overhanging leaves.
The short cremaster is attached to a silk pad by its short curved
This stage lasts c.3 weeks. But those individuals
that pupate in early winter may overwinter in this
stage for up to 7 months.
The adults emerge from pupation and are on the wing during May and June
and again in August to
September and in mild weather there may be a small third generation in
September to October.