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brimstone   <>   gonepteryx  rhamni   <>   bug ruibheach

DHardiman 2003  

Habitat: This species is distributed locally where larval food plant is found, mainly in limestone areas of the midlands and west of Ireland.  
It has only one annual brood.
Flight Times:  The adult  may be found at almost any time except mid-summer. 
Larval food plants: 
Rhamnus catharticus
                             Alder Buckthorn  Frangula alnus
Hibernation:   Overwinters as an adult butterfly

The male Brimstone is often found quite a long distance from its food plant.

The Brimstone hibernates as an adult but often comes out of hibernation on mild, sunny winter days returning later to resume hibernation.


Life 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 weeks.

  Brimstone ovum
          DHardiman 2002

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.

Brimstone Pupa

     DHardiman 2002

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 hibernation site.

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 tint.  
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.

    Male Brimstone

Female Brimstone               DHardiman 2002




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