Black-veined White - a life story

[Chris Jackson]

Hi Folks,
I've cobbled together a life story following many hours spent idly whiling away my time in the scrub in the south of France with my camera - enjoy:
A courting pair

Mating

Egg laying

A clutch of eggs - here on hawthorn, 24th June

After hatching, the 1st stage caterpillars form a silk nest, 7th July. They grow little until the following spring.

The cats have over-wintered and are 4 mm long when Spring arrives, 30th March the following year

Here others are 7 mm long on Wild Pear, waiting for the Spring growth, 30th March

Here the cats are 21 mm long on Wild Pear, end of April

Here, other cats are 28 mm long on Hawthorn, end of April

Many cats are parasited by Hymenoptera or Diptera - here in May. The parasites lay their eggs inside the bodies of their host caterpillars. The larva grow inside the bodies of the cats while eating them inside out. The larva of the parasites break out of the bodies of their hosts and form cocoons, the cocoons themselves sometimes being parasited in turn.
The cats seem to feel a duty of protection toward their parasitic 'offspring' that finally kill them.

This cat is dying after having accomplished its protective role with respect to its parasites.

This cat is ready for pupation on thym, but is upside down !!

The same cat has pupated on 8th June whereas the flight period is already underway since 26th May at this altitude

Seriously worried about the non-emergence of the butterfly after 3 weeks pupation, I recovered the pupa. The following day the story became clear. The arrow shows the assassin:

Parasite exit hole from the pupa

Here is the parasite (5mm long) after having devoured the developing butterfly and exited the pupa

The culprit's ID will be published when it is known.
Other Black-veined Whites do manage to complete their life cycle fortunately.
Ainsi va la vie.
The Black-veined White was killed off in the UK through the use of pesticides in the 1920s - it seems to me that their lives are difficult enough without pesticides?
Chris

Edit: The parasite is Brachymeria tibialis

[David M]

Fascinating commentary, Chris, and yes, butterflies in general have difficult enough lives without we humans peppering our crops with poison.

[NickMorgan]

Really interesting Chris, and great photos. It amazes me sometimes that we have any butterflies left at all when you think of all of the perils they face through all their stages of life.

[essexbuzzard]

Really enjoyable sequence, Chris. Thanks for sharing. Considering how common hawthorn is in GB, including in hedges, gardens and roadside verges, where it is not sprayed, I’m not convinced this is the only reason BVW died out, though it may have been the final nail in the coffin. Perhaps it was in trouble already?

Whatever the cause, it’s a great shame it has gone. Black-veined Whites are one of the pleasures of butterflies in Europe.

[Sylvie_h]

Hi Chris,

What a sad story and beautiful observations. It is surprising how much parasites there are on one species of butterflies.
I wonder how much chance the caterpillars have against wasps and wonder why they have not found a way of defending themselves yet....
The wasp which had exited from the pupa is some kind of Chalcis I believe. There are different species of Chelcis in France but not sure which one it is. Nevertheless, I find the relationship between parasites and hosts fascinating ….
Very interesting post and thanks for sharing.
If I find any information on the Chalcis, I will let you know.
Sylvie