Ctenichneumon Thomson, 1984

Ctenichneumon is a moderately diverse genus of medium-sized wasps mostly ranging from iridescent blue to plain black in color. However, one aberrant species present in at least Utah and California is entirely light brownish-red. There are 14 described species and an unknown but significant number of undescribed species in the West.

Ctenichneumon belongs to a group of genera, including Ichneumon that all share a longitudinally striate postpetiole. More specifically, Ctenichneumon is a member of the Amblyteles genus-group which includes Diphyus, Eutanyacra, Limerodops, and Spilichneumon, among others. It is easily differentiated from these related genera based on the typical color pattern described above, but more importantly, by the large, deeply-impressed gastrocoeli and completely absent thyridia. This combination of traits does not occur in any other Nearctic ichneumonine genus.

Due to the similarity in color, Ctenichneumon may be confused with Coelichneumon and other genera with iridescent blue species such as Platylabus or Patrocloides.

Biology

Palearctic Ctenichneumon spp. have been recorded as parasites of noctuids. There are no recorded rearings of Nearctic species.

Diagnosis

• color usually black or iridescent blue
• postpetiole of first metasomal segment longitudinally striate
• gastrocoeli well developed and deep impressed but thyridia absent
• male flagellum with well-developed bristle ridges
• female metasomal apex amblypygous