Species Diplazon laetatorius - Common Hover Fly Parasitoid Wasp

Hover fly parasite (note: this isn't actually a parasitic wasp but rather parasitoid)

Diplazon laetatorius (Fabricius, 1781)

The tricolor hind tibia readily distinguishes this species from other Diplazontinae.

Larvae feed on a wide variety of dipterous hosts, especially aphidophagous syrphid flies; it also attacks some Coleoptera and Lepidoptera.

Adults have been observed to feed on syrphid eggs.

"I feel certain that reports of this species parasitizing Coleoptera and Lepidoptera are erroneous. Taxacom, for example, reports whatever has been listed in literature, without regard to the scientific accuracy of the source, the rearing methods use, and so on. Of course, if the syrphid fly host instead of Diplazon laetatorius had appeared in the rearing cages (or whatever), it wouldn't have been reported as a predator or parasitoid of Coleoptera or Lepidoptera." — Bob Carlson

It is thelytokous throughout most of its range and males are extremely rare.

This species likely has the greatest geographic range of any ichneumonid (and perhaps any hymenopteran) having been recorded from the Canadian Arctic to Argentina, from Norway to South Africa and Japan to New Zealand including many remote oceanic Islands. As with the subfamily, the vast majority of host records of D. laetatorius are from Syrphidae (20 genera). Its wide range is likely a result of human agriculture that has spread it along with aphids and aphidophagous syrphids. Because it parasitizes aphidophagous syrphids it can be considered a pest.

It has been reported to parasitize as many as 75% of syrphid larvae.

Townes, H. (1971). The Genera of Ichneumonidae, Part 4 (Vol. 17). Memoirs of the American Entomological Institute.(1)

GBIF