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Mutillidae are a of wasps whose wingless females resemble ants. Their common name velvet ant refers to their dense hair which may be red, black, white, silver, or gold. They are known for their extremely painful sting, facetiously said to be strong enough to kill a cow, hence the common name cow killer or cow ant is applied to some species.

The earliest-known velvet ants are specimens from the Dominican Republic preserved in amber some 25 to 40 million years ago.

Description

D asymutilla sp.

They invade the nests of wasps and bees so their integument is very tough and roughly textured to protect against stings. Like related families in the Vespoidea, males have wings but females are wingless. They exhibit extreme sexual dimorphism; the males and females are so different that it is almost impossible to associate the two sexes of a species unless they are captured while mating. In a few species the male is so much larger than the female that he carries her aloft while mating, which is also seen in the related family Tiphiidae.

In all Hymenoptera only the females sting because the stinger is a modified ovipositor. Like all wasps they can sting multiple times. A structure called a stridulitrum on the metasoma is used to produce a squeaking, chirping, or humming warning sound when handled.

Mutillidae have the only wingless female wasps bearing hair-lined grooves on the side of the metasoma called felt lines. The segments of the mesosoma are fused dorsally, a feature also unique to this group. Only one other vespoid family (Bradynobaenidae) has felt lines, but the females have a distinct pronotum and an elongated ant-like petiole.

Behavior

Mature mutillidae feed on nectar. Although most species are strictly nocturnal, females of T. thisbe^[ambiguous] are sometimes active up to two hours before sunset. Guido Nonveiller (1963) hypothesized that Mutillidae are generally stenothermic and thermophilic; they may not avoid light but rather are active during temperatures which usually occur only after sunset but on cool overcast days could occur earlier.

Life Cycle

A female velvet ant.

The male locates a female on the wing and mates. The female then enters an insect nest, typically a ground-nesting bee or wasp nest, and deposits eggs near the larvae or pupae. Her young develops as an idiobiont ectoparasitoid, eventually killing and eating its immobile host. A few European species have been known to invade and raid^[ambiguous] bee or wasp nests.

Range

Mutillidae occur worldwide, with some 5000 species, mainly in the tropics. They are especially common in desert and sandy areas, with most of the over 400 North American species found in the Southwestern United States and adjacent parts of Mexico, with others found in generally sandy regions throughout the United States and Canada; the same habitat where their hosts are most diverse. Many species are nocturnal.

The Family Mutillidae is a member of the Superfamily Vespoidea. Here is the complete "parentage" of Mutillidae:

• Domain: Eukaryota Whittaker & Margulis,1978 - eukaryotes
  • Kingdom: Animalia Linnaeus, 1758 - animals
    • Subkingdom: Bilateria (Hatschek, 1888) Cavalier-Smith, 1983 - bilaterians
      • Branch: Protostomia Grobben, 1908 - protostomes
        • Infrakingdom: Ecdysozoa Aguinaldo Et Al., 1997 Ex Cavalier-Smith, 1998 - ecdysozoans
          • Superphylum: Panarthropoda Cuvier
            • Phylum: Arthropoda Latreille, 1829 - Arthropods
              • Subphylum: Mandibulata Snodgrass, 1938
                • Infraphylum: Atelocerata Heymons, 1901
                  • Superclass: Panhexapoda
                    • Class: Insecta C. Linnaeus, 1758 - Insects
                      • Subclass: Dicondylia
                        • Infraclass: Pterygota - Winged Insects
                          • Superorder: Hymenopterida
                            • Order: Hymenoptera C. Linnaeus, 1758 - Ants, Bees, and Wasps
                              • Suborder: Apocrita - Ants, Bees
                                • Superfamily: Vespoidea
                                  • Family: Mutillidae - Velvet Ants