Darwin wasps

  Ichneumon wasps in the garden, menacing with their twitchy antennae and jerky movements, taking a break from parasitising insect larvae to satisfy their own energy needs.

Black Darwin wasp Ichneumon delicatorius

Yellow-striped Darwin wasp Ichneumon xanthorius feeding on nectar from lovage flowers. Its larvae develop parasitically inside the caterpillars of moths and butterflies.

 They are known as Darwin wasps because their gruesome life cycles played a role in undermining the great naturalist’s belief in a benevolent creator. “I cannot persuade myself,” he wrote, “that a beneficent and omnipotent God would have designedly created the Ichneumonidae with the express intention of their [larval stages] feeding within the living bodies of caterpillars.”

Assassin

Watching this little hymenopteran (can anyone help with the identification?), only about a centimetre long, working its way through the florets of the grasses around my garden pond, provided a chilling insight into this deadly parasite’s hunting technique. Equipped with a long egg-laying tube (ovipositor), it parasitized insect grubs inside the grass florets without ever seeing its prey. The pictures give a clue to how it manages this. It moved from floret to floret, pressing its antennae against each in turn (bottom picture). How did it find them? Was it scent picked up by its antennae tips, or did they detect vibrations from a wriggling, hidden victim? I have no idea, but what is certain is that as soon as it located a hidden host the parasite slid that stiletto-like ovipositor into a floret (top picture), presumably laying an egg in an unfortunate victim whose destiny was to be eaten alive by the hymenopteran's hatching larva.