Wasp Spider Invaders

I stumbled across my first wasp spider (Argiope bruennichi) in the summer of 2008. We’d been mowing a road verge with the National Trust and whilst sweeping up the grass noticed this extraordinary looking creature:

Female wasp spider (Argiope bruennichi)

It’s not what you’d expect from a British spider – the distinctive black, white and yellow stripes give it a dramatic appearance, and at 2cm it’s fairly large – something you might imagine encountering in the tropics, shortly before it bit you and ruined your holiday!

Sure enough it’s a foreign invader, more commonly found in the Mediterranean and first recorded on UK shores in 1922. Since then it’s made the south coast its home and, as conditions have warmed, has spread steadily north in recent years.

The Isle of Purbeck is at the southern extreme of its range in this country so it must have been present for some while. The following summer the female spiders were present in large numbers in a meadow at Durlston Country Park outside Swanage and I photographed them a little hastily with my point-and-click at the time.

When I acquired a DSLR camera capable of HD video recording this year, and a decent macro lens, I decided the wasp spider invaders would make a good subject for a short video:

Canon 550D | Canon EF-S 60mm Macro | Adobe Premiere Pro CS4

I couldn’t find the spiders in the places I’d spotted them previously, but while clearing another fenceline with the National Trust we stumbled across this small colony living on the edge of Godlingston Heath on the Studland peninsula.

Over a couple of visits I shot some decent footage and stills at very close range with the 60mm macro lens. The conditions were a little breezy, which makes life difficult at very shallow macro depths of field but I’m pleased with the results.

Wasp spider

Wasp spider macro detail

Try as I might I could not track down the male wasp spider, which is smaller and quite dull in colour. I would also have liked to include some footage of the spiders’ large egg sacs, but the weather turned wet and stormy towards the end of the month and by the time I returned the colony was washed out. Only a couple of females remained and no egg sacs.

Burnet Bodysnatchers

Caterpillars get a raw deal.

It’s true that the lucky winners in life morph into fabulous winged creatures which transcend their earthy origins, but a great many of their brethren seem destined to become nothing more than a convenient snack for any number of passing creatures.

Walking along the Purbeck coastal downland in mid summer I discovered a particularly unpleasant variation on this theme.

I was hoping to photograph some Adonis blue butterflies – a local speciality – but became mesmerised by a collection of tiny cocoons fastened to a grass stem. The more I looked, the more cocoons I found, but all appeared to have been vacated.

I couldn’t think what they might be, until additional exploration eventually uncovered their unfortunate victim nearby: a burnet moth caterpillar, seemingly tied to the stake:

Burnet caterpillar with cocoons

Burnet moth caterpillar parasitised by wasp larvae

This time the larvae were all too evident, as they appeared to be burrowing out of the caterpillar’s skin!

Further research reveals a fascinating tale of nature’s indifferent ingenuity:

The perpetrators in this instance are a species of Braconidae wasp which lay their eggs inside caterpillars.

When they hatch the larvae consume the caterpillar from the inside, but are careful to spare vital organs in order to keep their victim alive. Eventually the larvae cut their way out using specially adapted sharp mouthparts. When they emerge they immediately spin cocoons attached to the caterpillar.

Recent studies suggest that the larvae influence the caterpillar’s behaviour to remain in place and guard the cocoons. Thus brainwashed, the creature may even spin it’s own silk around the cocoons to further protect them. The wasps later hatch and the zombified caterpillar dies of hunger. Ain’t life great!

The Braconidae wasps don’t get it all their way however, as another variety of Ichneumon wasp parasitises the Braconidae pupae inside their own cocoons.

I found an example of this behaviour a bit further along the same stretch of coastal downland. The cocoons had been deserted by their caterpillar protector for some reason, which left them exposed.

Parasitic wasp

Ichneumon wasp parasitising Braconidae wasp pupae