About a month ago I found a small spherical mantis ootheca on a dry grass stem, sort of worn out, though partially viable I thought. A few weeks later I woke up to a test tube filled with more than a hundred chalcid wasps — red eyes, stumpy antennae, blue metallic bodies with some iridescent flashes on the wings, enlarged raptorial-like hindlimbs and protruding ovipositor — all in cute little bodies under three millimeters in length. Evidently, this egg case had been subject to parasitism by these tiny fiends, with even more wasps dispersing out of the bottom two exit holes they carved out from the interior. If you look closely you can see the ovipositor of one wasp through the translucent ootheca and the forelegs of another. These wasps belong to the family Torymidae, the only clade known to be parasitoids of mantids (… someone correct me if I am wrong, it would be interesting to know if this association has evolved more than once).
I’ve been really fortunate to witness chalcid parasitoid behavior multiple times. My first experience with them was in the field in Costa Rica. As I closed in on a bark mantis ootheca (genus Liturgusa), two males were running around on the outside of the ooth erratically, impatient for what was about to come. A female then erupted out of the egg case’s spout, and the two males simultaneously jumped on her, striving to connect and successfully reproduce. It was amazing to witness this event in situ, the male who came out victorious and the other who became sessile and perhaps lost hope in his paramount goal in life. In torymid wasps it is common for the males to emerge prior to the females, increasing their chance of reproducing at the opportune moment — just before the female’s dispersal and search for an ootheca to drill in to. Like most insect ovipositors, those in chalcids are flexible and serrated, easily slipping into the mantis’ foam package with the direction of the wasp’s elongated hindlimbs.
Back to the current story. A few days later I examined the vial again, and by sheer force of will, a sole mantis had managed to survive the tissue draining onslaught of the parasitoids. How confusing it must be to enter the world surrounded by hundreds of your greatest nemeses, all in an enclosed space. The mantid likely belongs to the subfamily Hoplocoryphinae of the family Thespidae. I’ve seen nymphs around, though I haven’t been able to find descriptions of their oothecae, which would confirm the identification. Instead of rearing this one, I placed it outside, where it will have many more rounds of almost negligible prospects of reaching adulthood. As is the exceedingly challenging life of almost any insect.
Photographed under controlled conditions with manipulation to get the wasp and mantid in the same focal plane [6]