Tachina

Hogweed umbels attract all manner of insect visitors, including this very striking fly Tachina fera, which has a gruesome life history. It has two flight periods, from May to early June and from July to September.

This tachinid fly lays large numbers of small eggs on vegetation and when they hatch the grubs, alerted by vibrations from an approaching potential host noctuid moth caterpillar, attach themselves to it  and bore into its body, where they develop as internal parasites. There are numerous tachinid fly species, illustrated at the Tachinid Recording Scheme web site.