Social Distancing Week 17. Ichneumon sarcitorius
Paul writes: I am always finding ichneumon wasps in and around my garden. Often they are running through the undergrowth, all the time twitching their long antennae. Then they’ll stop on a leaf or a flower to have a search round. They take a nice photograph but unfortunately most of them can’t be identified, they need a much more detailed examination. They all have a similar body shape, long and narrow with a wasp waist, and long antennae. Sizes vary from 2mm to 40mm. However last week I struck lucky and found this one. It’s about 14mm long and the shape and colour of the markings mean it can be identified as a male Ichneumon sarcitorius. I also found a female at the same site. They have different colours and markings from the male but are also identifiable.
There are about 2500 British species of Ichneumonids, the majority are parasitoids of other invertebrates. They lay their eggs in or on a host, which the larvae feed on and eventually kill. Very little is known about their life cycle or host selection. Ichneumon sarcitorius is known to use the pupae of moths.
For reasons mentioned above the distribution of Ichneumonids is difficult to establish but I know they are found in most habitats throughout the country. The Natural History Museum has recently published a guide to identifying a few of them from photographs (see here) so with this as a guide I’m hoping to be able to add a few more to my site list and help fill in the distribution maps.