Our insect of the week for October 6, 2025 is the wasp mantidfly, Climaciella brunnea [NEUROPTERA: Mantispidae], described by the American entomologist Thomas Say in 1824. Note the raptorial forelegs (similar to what we see in mantids). Nice example of convergent evolution as these insects are also predators.

It is called the wasp mantidfly as it mimics members of the wasp genus Polistes (paper wasps).

This species is native to central Illinois, and ranges from southern Canada to Nicaragua.

First instar larvae are campodeiform (with legs, antenna, and a flattened body). They also have a caudal sucker. They use phoresy to find their prey. The first step is to find a spider (typically a wolf spider – Lycosidae). They attach to the spider by waving their body back and forth. They remain on the carapace of the spider until it mates. They typically subsist on the spider’s haemolymph until the spider mates. If they are on a male spider, they transfer to the female; otherwise, they remain on the female until it begins to lay eggs. The larva moves into the sticky fluid the spider uses to construct her egg sac and become trapped within the sac. The larva then feeds on the spider eggs in the sac.

I couldn’t make this up if I wanted to. Imagine the necessary steps for this behavior to evolve.

The specimen in this photograph was collected by Mark DuBois in Peoria County, Illinois in 2019. The photo is the result of stacking the focused part of 269 separate images.