Tachinids are fairly easy to identify: they have very long spines all over their body. Their flying habit is also easily recognisable, once identified: they fly low and slow over vegetation, looking for their hosts, and dart under leaves very suddenly, just like Ichneumonids. Tachinids are ectoparasites: they lay their (multiple) eggs on the outside of the host larvae. The Tachinid larvae then hatch out and eat the host while it is still alive. This can result in a very messy corpse indeed.
Moving on from parasites, we come to predators. Everyone knows about mimicry, where a harmless insect, such as a hoverfly, can have black and yellow bands just like a wasp. This similarity affords the hoverfly protection from predators such as birds, which avoid eating insects that might be unpleasant or harmful. In the following case, however, we have the reverse situation. This is an Ectemnius sp. wasp:
A few points are worth noting:
1) the body is black and yellow, as you might expect from a wasp, but the yellow bands are very rounded.
2) the head is very large, giving the impression of large eyes.
3) the antennae are bi-coloured, hinge in the middle, and can be pulled up into notches in the 'face', leaving a yellow area in the middle of the face.
Has this rung any bells yet?
Going back to the points above:
1) the yellow bands on hoverflies can be rounded.
2) hoverflies have large eyes
3) hoverflies have short antennae that sprout from the top of the head, and often have a yellow face.
So the inescapable conclusion is that this is a wasp which is trying very hard to look like a hoverfly.
Why?.....because it is predatory only on hoverflies, which it catches and then feeds to its young. It resembles a hoverfly so that it can sneak up on them and catch them unawares.
So here we have a wasp that is pretending to look like a hoverfly that is pretending to look like a wasp. Talk about a wolf in sheep's clothing...
2 comments:
Stunning pics, especially that close-up of the head - but why didn't you ask it to pull in its antennae? :-)
I occasionally see these wasps, but have yet to see one successfully sneak up on and take a hoverfly.
Incidentally what is the technical difference between a parasite and a predator? You could argue that those tachinid larvae are predators on their host/prey, they just eat their dinner very, very slowly....
The more one looks at nature the more complicated and remarkable it becomes - and it is crystal clear that to preserve/conserve it one *must* preserve the entire ecosystem, creepy-crawlies and all.
>Incidentally what is the technical difference between a parasite and a predator?
Well, to be absolutely accurate, Ichneumonids and Tachinids should be called parasitoids, because 'proper' parasites don't actually kill their hosts. So we have:
Parasite: feeds off a host without killing it
Parasitoid: feeds off the host, eventually killing it
Predator: this feeds off the prey, usually after it has killed it (but it might not bother to wait that long).
>The more one looks at nature the more complicated and remarkable it becomes
That's what keeps me going, and I find something new every day.
>to preserve/conserve it one *must* preserve the entire ecosystem, creepy-crawlies and all.
Amen
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