urbpan | 280 days of Urbpandemonium #6 (Reply)

280 days of Urbpandemonium #6: On our urban nature walk we tried to identify a shrub: it looked like a blueberry bush but was very tall. This gall confirmed our suspicions. This was the nursery for a bunch of tiny blueberry stem gall wasps,Hemadas nubilipennis. The tiny gravid wasp lays her eggs in the stem of the blueberry, which causes this woody growth to envelop and protect them.

The many little holes on the outside of the gall are the exit holes of the young, who grew to adulthood inside, and chewed their way out as grown wasps to repeat the cycle. Or perhaps the holes were made by a parasitoid wasp: at least four different species of other wasp are known to lay their eggs in the cells of the blueberry stem gall wasp, where their larvae feed on the larvae of the gall-maker, and benefit from the gall’s protection.