Although Priocnemis susterai is primarily a nectar feeder, it preys exclusively on spiders in which to lay an egg. The spiders are paralysed with a venomous sting and then dragged into a crevice or other protective nest site in the soil. The egg hatches, and the emerging larva feeds on the paralysed prey. After the spider has been consumed the larva pupates in a silky cocoon and overwinters, emerging as adults in spring and summer months.
The long legs of the adult wasp enable it to crawl rapidly over the ground in search of its prey as well as avoiding the spiders’ own venomous fangs.
The species is widespread in open woodland and downland in southern and central England, and may be seen from April to August either in flight or feeding on nectar from wood spurge.
This is a focus-stacked image of a female specimen.
