Unknowns Regarding the Biology of North American Ichneumoninae
Despite being large, colorful, and commonly observed, our understanding of the biology of North American ichneumonines is severely limited. The following is a list of some of the most jarring examples, which include some of the most common ichneumonines. This is by no means a comprehensive list since the majority of NA ichneumonine species do not have host records, but are just the most egregious cases. There are many opportunities for interested individuals (both professional scientists and amateurs) to get involved and make significant discoveries.
Background
With the exception of Colpognathus, which emerges from the mummified larval remains, all ichneumonines emerge from the host pupa. But caterpillars, prepupae, or pupae can all be attacked by different species. Often, we only know that a particular species emerged from a certain host but not which stage was attacked.
In some cases, however, we can tell which stage is attacked purely based on the morphology of the female metasomal apex. Specifically, all amblypygous species attack the larval stage of their hosts, and all oxypygous species with a scopa/hind coxal tooth attack the pupal stage. For oxypygous species with an unmodified hind coxa, the host stage that is attacked cannot be confidently determined based on female morphology alone.
Beyond which species of host is attacked at which stage, many other aspects of ichneumonine biology are unknown. For example, a small but not insignificant number of genera have a unidentate, sickle-shaped mandible which is presumably an adaptation for either the females accessing their hosts or when emerging from the host pupa.
Ichneumonini
Amblyjoppa magnus. Our only species of Amblyjoppa. The genus is known to attack sphingids but what species does A. magnus attack?
Catadelphops. Genus attacks sphingids but no records for our two NA species.
Coelichneumonops. Present in northern/high elevation boreal areas. No host or other biological information.
Limonethe. Only reliable host record is from Nymphalis antiopa but is the larva or pupa attacked? The semi-amblypygous female metasomal apex and presumed difficulty of accessing a hanging chrysalis would suggest the former.
Lobaegis. Somewhat rare but biology completely unknown. What is the host? How is it using the sickle-shaped mandible and the third inner tooth?
Neamblymorpha milva. Monotypic genus present in the Northeast. This species is fairly large and commonly observed but there are no host records. It is amblypygous so attacks larvae. Heinrich (1961) noted that it is commonly seen in shady, moist spots near ferns.
Narthecura. A primarily Neotropical genus that gets into Arizona. No host records or other biological information.
Neodiphyus. Present in Florida. Amblypygous so attacks larvae but no host records or other biological information.
Plagiotrypes. Somewhat uncommon and present in eastern US. No host records or other biological information but of particular interest due to the odd metasomal apex of the female. It has an upwards-curved ovipositor and the anterior of the apical tergites is unsclerotized, somewhat similar to the ctenopelmatine genus Notopygus which attacks leaf-rolling sawflies. Does Plagiotrypes do something similar? How exactly is it using that ovipositor?
Setanta. One of the most common and observed species in the East and Southeast. It is amblypygous so attacks larvae but there are no published host records.
Phaeogenini
Eparces. Seems to be commonly found around marshy areas. Is the host feeding within reeds? Why is Eparces so elongated (presumably to access hosts)?
Jethsura. Common and widespread in the East. No host records, however, in the latest revision I hypothesized that Jethsura species attack the larval stage of their hosts.
Platylabini
Ambloplisus. Fairly common and recognizable. Undoubtedly attacks the larval stage of its host which is likely a geometrid.
Tropicolabus. Known only from two specimens. No host records or biological information.