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BLATTARIA 111
come forth to scurry across the floors, walls, and ceilings with amazing speed.
Under present sanitary conditions cockroaches are not so common as they once
were, but they are far from being divorced from man. Native species are to be
found out of doors under stones, logs, wet leaves, and debris of all kinds. Certain
species live in ants' nests, others are common on vegetation, and a few,
like Rhicnoda natalrix Shelford, of the tropical East Indies, live near water and
readily dive to the bottom where they remain for some time.
As a group they are long-lived im;ects. Although the life history of some of
the domesticated species occupies but a few months, many species require from
1 to 5 years to complete a generation. There are from five to seven ecdyses, and
the nymphs greatly resemble the adults. All have the habit of cleaning the
antennre and feet with the mouth. They are mostly gregarious, and certain
species of Paneslhia live in family communities in burrows in the soil. Still
others are solitary. A few are attracted to lights.
Cockroaches occur throughout the world with the exception of the polar
regions, and even these are penetrated in ships. They are, however, chiefly
tropical and attain their greatest development in the hot, moist jungles. There
are approximately 250 genera, 2,250 species, three families, and 23 sllbfamilies.
According to Schroder (1925) the species are distributed as follows: Neotropical
660, Ethiopian 610, Indo-Malaysian-Papuan 500, Auslralian 250, Palcearctic
160, and Nearctic 70.
KEY TO IMPORTANT FAMILIES
L Hind wings, when present, with anal area large and with many folds 2
Hind wings, when present, with anal area small and with but aile or two
folds . CORYDIIDlE
2. Females with valves on the seventh sternite .
Females without valves on the seventh sternite
BLATTIDJE
PHYLLODROMIIDlE
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Family CORYDIIDJE Brunner 1865 (Co-ry-di'i-dre, from the Greek KOPVS, a
helmet).
Large- and small-winged, brachypterous, and apterous species forming a
heterogeneous group. Some forms are large, broad, convex, beetle-like, showy
roaches, while the myrmecophilous species are very small and somber in color.
The Pacific roach, Euthyrrhapha pacifica Coquerel, is probablY the most important
species of this family because of its wide tropical distribution. It is a
small brown'species with an orange spot on each tegmen and with rather long
legs, It is both diurnal and nocturnal and runs in an erratic manner. In the
semiarid southwestern part of the United States there are several interesting
species belonging to the genus Arenivaga, the commonest of which is the erratic
roach, A. erratica (Rehn), a small to medium-sized reddish-brown species
10-20 mm. long. The females are wingless and the males winged. They ordinarily
occur under stones.