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Mutillidae or velvet ants, also known as cow killers, are not actually ants but a type of wasp. They get their name from their hair, which ranges from red and black to completely white, or may be silvery or golden. Their integument is very tough and roughly textured, providing protection against the stings of the wasps and bees whose nests they invade. As in other related families in the Vespoidea, the males have wings, but females are completely wingless. They exhibit extreme sexual dimorphism- the males and females are so different in appearance that it is, in fact, almost impossible to associate the two sexes of any given species, unless they are actually captured in the act of mating. In a few species, the male is so much larger than the female that he carries her aloft while mating (also seen in the related family Tiphiidae).
They are known for their extremely painful sting, the venom of which was jokingly stated to be powerful enough to kill a cow, hence the nickname "cow killers." As with all Hymenoptera, only the females sting, and like all other wasps and bee (except honeybees), they can sting multiple times. If handled, they also have a structure called a stridulitrum on the metasoma which they use to produce a squeaking, chirping sound to warn would-be predators.
The family can be recognized best in the female; they are the only wingless female wasps that have hair-lined grooves on the side of the metasoma (called "felt lines") and in which the segments of the mesosoma are all fused dorsally. Only one other vespoid family (Bradynobaenidae) has felt lines, but the females have a distinct pronotum and an elongated ant-like petiole. The earliest-known velvet ants are believed to be specimens from the Dominican Republic preserved in amber for some 25 to 40 million years.
Reproduction and life cycle
The male wasp flies around, searching for females. After mating, the female seeks out an insect's (typically bee's or wasp's) nest. Upon finding a suitable host, she lays her eggs near the larvae or pupae. The mutillid larva develops as an idiobiont ectoparasitoid, eventually killing and eating its immobile host. A few European species have been known to invade and raid beehives.
Diet
Mature mutillids feed upon flower nectar.
Range
Mutillids occur worldwide, with a total of some 5000 species, mostly in the tropics. They are especially common in desert and sandy areas, with most of the over 400 North American species found in Texas, New Mexico, Arizona, California, and adjacent parts of Mexico; the same regions where their hosts, ground-nesting bees and wasps are most diverse. Many species are nocturnal, avoiding the searing heat of their desert environment.
References
- Lorus J. Milne, National Audubon Society Field Guide to North American Insects and Spiders (Audubon Society Field Guide) (Turtleback)(1980) Knopf. ISBN 0394507630.
"Mutillidae"