These “weird house flies” are ensign wasps and they help to manage cockroach populations. ... The wasp pupates within the cockroach egg case and the adult emerges out when ready. These wasps are not known to sting humans.

Does ensign wasp sting or bite?

The ensign wasp is one of the odder insects found occasionally in homes. A small insect, only 5-7 mm long, it does not sting or bite. In fact, it does no harm; but it is a beneficial parasite of at least three household cockroaches, the American cockroach being the most common.

Should I kill ensign wasp?

Adult female Ensign Wasps often come into houses searching for oothecae. Unfortunately, many people kill them, thinking they are harmful pests when the truth is just the opposite. So if you see one, don't destroy it. Either leave it alone or put it outside.