BLATTIDiE. 
57 
quarter of an inch in length to larger robust forms which measure nearly 
two inches. They are coloured in sombre sheds of brown and black, 
only a few species with conspicuous bands or spots of yellow or orange 
which may constitute a degree of warning coloration and are usually 
found in the diurnal species living to some extent exposed. The an¬ 
tennae are long and filiform, functioning as delicate sense organs ; the 
mouth-parts are of the non-predaceous biting type, the mandibles short 
and massive, the labial and maxillary palpi well developed. The body 
is generally soft, the chitinous plates of the integument not firmly united 
and the chitin usually less thick than in other insects. The flattened 
body and slippery surface 
enable the insect to hide 
in crevices and render it 
more difficult to capture. 
The abdomen terminates 
in a pair of short jointed 
cerci, whose precise func¬ 
tion is not known. The 
legs are long, thickly 
spined and formed for 
quick running ; the first 
pair are reduced in some 
species. (Fig. 8.) Males 
and females are generally 
similar in appearance, the 
former in some instances 
with a pair of slender 
stvles at the genital open- 
Fig. 8 —POLYPHAGA jEGYPTIACA. . 
From below. ing. In several species the 
wings and tegnima are absent or only imperfectly developed, this being 
correlated with the general disuse of the wings throughout the family. 
It is difficult to distinguish the wingless adult from a nymph of a winged 
form ; the presence of lobes at the hind angles of the mesonotum and 
metanotum shows the insect to be a nymph of a winged species, in most 
cases. 
The life-history of all known species agrees in the general features. 
