PARASITIC WASPS PART TWO

Copidosoma sosares - a polyembryonic Chalcid wasp that feeds in Parsnip Moth larvae

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 some Hogweed stems that I had supplied them with to pupate in. 

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 its skin?

I dissected one of the larva and was taken aback by the sight of many dozens of parasitic wasp grubs inside! 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 with their antennae tucked back over their backs apart from the odd one just coming around as the temperature rose.

At 2.5mm they are not one of the more colourful of parasitic wasps and they were tricky to photograph as they quickly become active as the light improved.

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 less patience than I normally would have, resulting in a damaged pupal case.

Enytus crataegellae - an Ichneumon wasp that feeds on Hawthorn Moth (Scythropia crataegella) larvae

Enytus crataegellae pupal cocoons, June 9th 2017. Each year the garden Cotoneaster has a small number of webs created by Hawthorn Moths (Scythropia crataegella). In among the small numbers of larvae and pupae I noticed similar numbers of these pied cocoons suspended by the webbing. I took a couple indoors to rear through and six days later the adult wasps began to emerge (below).

Gambrus bipunctatus - an Ichneumon wasp that feeds on Drinker moth larvae

A Drinker moth cocoon found near Boothwood reservoir during a trip with the Halifax Scientific Society on July 3rd 2022. It was taken back in the hope that I might see my first female Drinker moth but instead wasp after wasp began to emerge, seven in all. The first exit hole is arrowed.

The first to emerge was this male, obviously without an ovipositer.

I was curious to see what was going on inside so I opened the cocoon up. As well the dead moth larva the wasp larvae had spun cocoons of their own on to that of the Drinker's.

Of the seven wasps to emerge four were females including this one complete with ovipositer. She specialises in laying eggs in large, hairy caterpillars in wet grasslands such as Reed Dagger, Rush Wainscot and Drinker.

Thanks to Malcolm Storey for the information and for the identification of this wasp.