(The word of the day is taken from the Torre Bueno Glossary of Entomology)

Mystax, hair on upper lip; in certain adult Diptera (e.g., Asilidae), a patch of stiff setae above the mouth, on the lower part of the median facial plate, above the vibrissae.

I chose this word because our class saw a lot of robber flies (Asilidae) yesterday. The first thing I thought of, in terms of a distinguishing feature, was their “mustache”. Now I know there is a technical term!

This is the only photo I have taken of an asilid, you can sort of see that the front of its face is fuzzy.

Check out this link for a great side shot of robber fly mystax.