LIBRARY

692 COLLEGE ENTOMOLOGY
without closed cells or anal lobe; cubital cell not originating beyond transverse
median vein. Abdomen with or without a short. simple petiole and a deep constriction
between segments I and II and II and III; apex of male with one or
more spines; female with or without visible sexual organs. Sexual dimorphism
is exhibited not only in the absence of wings in the females but also by a difference
in colors and in size, the females being usually larger. Females make a
squeaking noise by stridulating.
These insects occur in hot semiarid and desert regions. and many species
are active during the hottest part of the day while others may appear at nightfall
and a few are nocturnal. The females may be found running over the
ground. Australian species also occur on the trunks of irees. The males of
FIG. 245. Mutillid wasps or velvet ants. A. Dasymutilla
$ackenii (Cresson); B, D. gloriosa (Saussure). (From Insects
of Western North America.)
certain species visit flowers. They are almost entirely parasitic in the nests of
ground-inhabiting bees and wasps, their larvre preying directly upon the larvre
of the host but not sharing its food. The host list is undoubtedly large, but
those most generally observed to be attacked are wasps of the genus Chalybion
Dahlbom and the bees of the genera Bombus Latr. and Nomia Latr. Some
species are known to parasitize ants, and African species are also reported as
preying upon the pupre of the tsetse flies, Glossina Wiedeman.
This large family, numbering more than 3,000 species, occurs mostly in
tropical and subtropical regions in Africa, Asia. Australia, North America, and
South America.
The most important genera are: Mutilla Linn., a large cosmopolitan group;
Dasymutilla Ashmead, Photopsis Blake, and Sphrerophthalma Blake are American;
Myrmosa Latr. and Dasylabris Radoszkowski are European; Traumatamutilla
Andre is South American; and Ephautomorpha Andre, with its 197
species, is Australian.