I'm pretty sure that's some sort of Ichneuman fly (actually a wasp)They sting caterpillars that live in your lawn or plants, and lay their egg inside them. This then hatches and the larval wasp eats the caterpillar alive from the inside out! AAAARGH!
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Shazzoir Old enough to know better young enough not to care,
Sat 1 Nov 2008, 9:15,
archived)