From the linked Hackaday article:

> If you don’t want to kill flies, wasps, bees, or other useful pollinators while eradicating the tiny little bloodsuckers that are the drone’s target, you need to be able to not only locate bugs, but discriminate mosquitoes from the others.

> For this, he uses the micro-doppler signatures that the different wing beats of the various insects put out. Wasps have a very wide-band doppler echo – their relatively long and thin wings are moving slower at the roots than at the tips. Flies, on the other hand, have stubbier wings, and emit a tighter echo signal. The mosquito signal is even tighter.

Fascinating engineering! Doesn't seem like it would be possible but it apparently is. There's also more visuals at about 17 minutes in the video embedded in that article, the signatures seem fairly distinct.

Imagine the sound a mosquito makes when it flies near your ear; it's quite distinct. I'm sure it's possible to distinguish mosquitos based on that (which is a factor related to the doppler signature mentioned).