Cycle of the Brimstone
The bottle shaped eggs are laid singly on the underside of leaves or
shoots. They can be laid up to a
height of 4 metres or more, between mid-April and the beginning of
July, but peaking in May and early June.
They are c.1.3mm in height and initially nearly white in colour but
after a few days become a deep yellow turning
grey before hatching. The egg stage lasts c.2
The mature larva is between 32-34 mm in length with a green body
which changes to a blue-green on the
lateral surfaces above the white supra-spiracular line. The body is
finely speckled with black bristles as is the green head.
Larvae can be found in June
and July. The early instar rests on the upper side
of the leaf along the midrid with it claspers at the base and feeds by
eating down through the
layers leaving the characteristic holes, the later instar rests on
the leaf edge or along a petiole
and eats the entire leaf. The larval stage lasts for c. 30 days.
When fully fed the larva leaves the food plant to pupate at a
suitable site - generally the underside of a leaf or stem
in low vegetation. The pupa is attached to the plant by the cresmater
and supported by a loose silken girdle.
Pupation takes place in July and lasts c. 2 weeks.
After emerging in early July the Brimstone butterfly is active untill
the end of September but does not mate and lay eggs until the following spring. Instead it feeds
extensively in order to fortify itself for hibernation.
It has a preference for purple and mauve flowers such as thistle,
purple loosestrife, buddleia and teasle.
Towards the end of September it goes in search of a suitable
The upperside of the male Brimstone wings are a clear lemon yellow but
the hindwings have a slightly greener hue. There is an orange spot in the centre of each forewing near
the upper margin and in the centre of both hindwings, and a series of small brown spots along the wing margins
at the termination of each vein.
The female Brimstone has much paler upper wings with a green
Both male and female have sharply angled wings and prominent veins and
when at rest the colour and shape of their closed wings closely resemble pale yellow leaves. This gives
perfect camouflage while
overwintering among the
holly, ivy or bramble leaves between September and May.
© DHardiman 2002