PARASITIC WASPS PART TWO

Copidosoma sosares - a polyembryonic, Chalcid wasp

The larva of a Parsnip Moth feeding on wild Parsnip at Walton Street, Sowerby Bridge on July 28th 2014. I collected six larvae over the space of a week to rear through. After a few days they stopped feeding and quickly burrowed into or down some Hogweed stems I supplied them with in order to pupate. 

One of the larva on August 10th. Often micro moth larvae take just two or three days to pupate after feeding is finished, so when they still appeared larval after five days I became concerned. What were those rows of objects visible under it's skin?

I dissected one of the larva and was taken aback at not the usual one parasitic grub inside but many dozens! After contacting Chalcid wasp expert Dick Askew he told me that these grubs were of the genus Copidosoma, a polyembryonic wasp where a single egg is laid in to the host and through the division of that egg a brood of very many, same sex individuals arise. 

The grubs soon pupated and the appearance of the caterpillar had darkened considerably. Nine days later on August 24th the adult wasps began to emerge en masse.

It was a very successful emergence with every single pupa giving rise to a fully formed wasp - all 102 of them from a single caterpillar! All that remained of the caterpillar was a desiccated head and body.

As if things couldn't get any more bizarre a couple of days later a second brood emerged from another larva producing no less than 193 wasps - yes I counted every last one. Overnight they preferred to roost under the neck of the jam jar like a scene from Aliens. Antennae tucked back over their backs apart from the odd one just coming around as the temperature rises.

Not one of the more colourful wasps, at 2.5 mm they can be tricky to photograph well in good light as they quickly become active.

672 Parsnip Moth, Aug.22nd 2014. As if to add insult to injury the only moth I managed to rear emerged with a crippled wing. This probably happened because when I was convinced all the larvae were parasitized I extracted them from the Hogweed stems with a little less patience than I normally would have, resulting in a damaged pupal case.

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