Thursday, 13 February 2014

Ichneumon

...is not a type of Pokemon, but actually a tiny parasitic wasp.

An ichneumonid or braconid wasp. Difficult to photograph through the microscope lense, 
my old camera was better for this!

I got excited when I first saw this under the microscope; I remember lectures on them at uni and how interesting they were. However, as they are very numerous in the malaise trap samples, the novelty has quickly worn off! Still, they are very beautiful and diverse.


Relatively big parasitic wasp (1cm in length) vs. small parasitic wasp

Parasitic wasps are an incredibly diverse group of insects with thousands of species in Britain alone. Like all other wasps, they have the three body segments, but the abdomen, antennae and stinger (ovipositor) are usually very long. The ovipositor is adapted for injecting eggs into other invertebrate eggs or larvae.

The ovipositor is maneuverable; here it is tucked under the abdomen. 
The sheaths or 'guides' normally enclose the ovipositor and help to guide and support it.

The wasp larva hatches out and feeds either within or on the body of the host; some sci-fi movies were almost certainly inspired by these little guys. Even poor ol' Darwin was quite darked-out by them, questioning why a benevolent god would ever create something with such a cruel lifestyle.


Their taxonomy (classification) is very difficult and instead of attempting to identify them, I'll be storing them indefinitely, saving them up for my retirement (which for my generation might be never). As well as ichneumon wasps, related groups such as braconids, chalcids, and eurytomids are likely present in our malaise trap samples, all of which make up a huge group with the general name 'Parasitica'. Some of these are used on a commercial level as biological control agents, keeping down your agricultural and greenhouse pests. Here is a selection of parasitic wasps I've come across so far:





This last one is possibly a gall wasp (Cynipidae). They are actually herbivorous and lay their eggs in host plants, often causing swollen growths called galls on leaves and stems.

Looking at stuff under the microscope is addictive and I've been putting in quite a bit of my free time sorting these trap samples. My make-shift portable invertebrate lab is coming along in leaps and bounds - I have most recently acquired a great big cardboard box!