Saturday, 25 November 2017

Life Cycle of the White Admiral

Now that autumn is moving towards winter, much of my time will be spent working in the wood. Rhododendron and bracken control is always on the agenda but coppicing, ride widening and wood thinning are essential in order to maximise potential breeding habitat for butterflies and moths.
Historically, most of our (now rare) woodland fritillary species would have been common in our wood. However, species such as the Pearl-bordered (Boloria euphrosyne), Small Pearl-bordered (Boloria selene) and Heath (Melitaea athalia) Fritillaries are highly unlikely to return naturally. I therefore focus my efforts on keeping the habitat right for species like the White Admiral (Limenitis camilla), which breeds in the wood in small numbers and also to encourage the Silver-washed Fritillary (Argynnis paphia) to increase its tiny population.
Life Cycle of the White Admiral (Limenitis camilla)
During the winter months, the White Admiral (L.camilla) hibernates as a tiny larva. It emerges from its hibernaculum in early spring and is fully grown by the end of May or early June. The pupa stage lasts for 2-3 weeks and the adult butterflies are usually on the wing from mid-June until the end of August. The ova are laid on honeysuckle leaves and the next generation of young larvae will start to build a new hibernaculum for the coming winter. 
A third instar larva remains close to its hibernaculum and a recently shed skin can be seen just above and behind the larva. (20th April 2015)

A fourth instar larva on honeysuckle. (28th April 2017)

A fifth instar larva on a honeysuckle stem. (21st May 2017)

The same larva is suspended from a stem node of honeysuckle about 15 feet from the ground and in 90% shade. (27th May 2017)

Two hours later and the larva has shed its final skin. The pupal membrane is yet to harden.
 (27th May 2017)

The same pupa (dark form).  (29th May 2017)

The same pupa (dark form). The pupa in this species has evolved to look like a crumpled honeysuckle leaf. The shadowy markings and reflective mirrors are clearly designed to break up its outline and make it less visible to predators. (4th June 2017)

Another final instar larva prepares to pupate beneath a honeysuckle leaf about 7 feet from the ground.
(31st May 2017)

The next day, the same larva has pupated. (1st June 2017)

The same pupa has adopted the more usual colour form. (2nd June 2017)

The same pupa. (4th June 2017)

The same pupa. (9th June 2017)

Sadly, the same pupa has been predated upon by a bird. Only the cremaster remains attached to the underside of the leaf. (11th June 2017)
The following three photographs are of a male White Admiral, freshly emerged from the dark form pupa. The left antenna is missing its tip and its left foreleg appears to be paralysed. After it had hardened its wings, I watched it fly up into the woodland canopy. (14th June 2017) 

The recovered pupa case shows that the pupa has sustained an injury or damage during its development. This has clearly interfered with the formation of the left antenna and is probably the cause of the paralysis in the left foreleg. (15th June 2017) 
My camera is not ideal for taking photographs of a pin-head sized ovum in subdued light but this image shows that the ovum is typically laid on the upper edge of a honeysuckle leaf.
(8th August 2017) 
The following photographs are of a second instar larva constructing its hibernaculum in preparation for the coming winter. The larva was about 6mm in length. (8th August 2017)

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