#ichneumonidae

Another likely undescribed species of Mesoleptidea!

Much like the one a shared a couple days ago, this specimen keys out to the common M cingulata when using existing literature. The dorsally black hind coxae and generally more strongly sculptured body distinguishes is. Preliminary genetic studies also show great divergence from all other Northern European species!

This alien-looking thing, Hybrizon buccatus, is in my opinion one of the strangest ichneumonids in Europe.

Members of the genus Hybrizon are parasitoids of ants. This is already unusual, but it gets stranger. They specifically target ant larvae, and their only opportunity to do so is when worker ants carry them outside the nest. Females swoop in, inject a egg, before quickly escaping the angry workers. This feels almost too specific to be real to me, but nature apparently found a way.

H. buccatus is tiny, with a fore wing only around 2-3 mm long. In Northern Europe it is the most common Hybrizon species, I’ve personally seen it hovering above ant-trails on several occasions.

You might think Sweden, essentially the birthplace of modern taxonomy, would be one of the last places to find undescribed species, but nope! Many Ichneumonids remain unknown to science, and this might be one of them. It belongs to the genus Mesoleptidea, a genus of sawfly parasitoids. Females can be distinguished from the similar M. cingulata, a very common species in Sweden, by the two white spots above the eyes and the distinct dark markings on the sternites.

Males are much harder to distingush. The basally darkened pterostigma is the only consistent character I've identified.

This is one of the rarest specimens in my collection. But rare doesn’t always mean hard to recognize, thankfully.

Lathiponus semiluctuosus (sometimes called Lathiponus bicolor) is one of the most distinctive European Ichneumonids in the subfamily Ctenopelmatinae. The back of the head is impressed in both sexes (not visible here sadly) and the ovipositor is strangely upcurved in females. Now that I type it out I realize it doesn’t actually sound like that much, but to a Ichneumonid enthusiast it’s a nice break from the nightmare that Ctenopelmatinae identification usually is.

[ID: Three photos of a black-colored ichneumonid wasp with orange, white, and black striped legs. End ID.]

If you keep an eye on dead spruce wood while walking through a northern European forest, there’s a good chance you’ll spot this species, Odontocolon dentipes, searching for hosts.

Like all other Odontocolon species, O. dentipes has a conspicuous ventral tooth on the hind femur, a character not found in any similar genus. Distinguishing it from other Odontocolon species is, however, much harder. Perhaps its most unique trait is that it appears to be more tolerant of humanity’s effect on nature than many of its relatives. The dominant forestry method in Sweden and neighboring countries is clear-cutting, a practice in which entire forests are cut down at once and then replanted. This creates perpetually young, managed, and homogeneous forests, lacking the structural variation many insect species need, especially those dependent on dead wood. Many ichneumonids that parasitize beetles in dead wood are therefore threatened, but O. dentipes seems to do quite well despite the odds. Let’s just hope it won’t be the only one left in 100 years.