Life and death on the Lesser burdock

The thistles have run out of steam so the pollinators have migrated to the other side of the park to a patch of Lesser burdock. This plant has wandered. Two years ago there was just one small plant and now there are four mighty specimens standing two metres tall. It has some fancy names: burweed, louse-bur, common burdock, button-bur, cuckoo-button and wild rhubarb.

The purple flowers are in bloom and provide nectar and pollen for bees, flies and butterflies, and the large leaves serve as platforms for grasshoppers and earwigs to sun themselves. The bumblebees are loving it and skit between the flower heads. Ants and Picture-wing flies run up and down the stalks. These are interesting little creatures – Richard Jones has written an informative article about them: Picture-wing flies.

 Braconid wasp and mummy cases

Braconid wasp and mummy cases

Yesterday I was wondering about some strange little aphid shells with holes that were attached to one of the stems. Further research identified them as ‘mummy cases’, caused by Braconid wasps. These tiny wasps are beneficial parasitic wasps, as one of their hosts is the aphid. After a female wasp injects her egg into an aphid, the larva slowly devours it. An aphid parasitised in this way is called a mummy. By the time the aphid dies, the fully grown larva has cemented it to the leaf surface and the aphid shell becomes parchment-like or black. The larva pupates inside the mummy, and when fully developed, the adult wasp cuts a hole in the casing and emerges. The empty mummy case, with its hole, remains on the leaf. There are lots of Braconid wasps flying around our Lesser burdock, and understandably not many aphids!