[citation needed] The females of some subfamilies (Diamminae, Methochinae, and most Thynninae) are wingless and hunt ground-dwelling (fossorial) beetle larvae, or (in one species) mole crickets.

[4] The prey is paralysed with the female's sting, and an egg is laid on it so the wasp larva has a ready supply of food.

In species where both sexes are winged, males are similar in size to the females, but are much more slender.

[5] As some of the ground-dwelling scarab species attacked by thynnids are pests, some of these wasps are considered beneficial as biological control agents.

[citation needed] The family has five extant subfamilies, which were previously placed in Tiphiidae before it was found to be non-monophyletic.