LIBRARY

132 COLLEGE ENTOMOLOGY
ANATOMICAL CHARACTERS-Continued
External
[ horax-continued
Legs - short and stout; cox;:e widely
separated; tarsi three-segmented, each
with a pair of claws and with or with·
out empodium or arolium.
Abdomen -ll-segmented (see text);
odorous glands on basal tergites of many
species.
Forceps - modified cerci; segmented in
young of some species; normally un·
segmented and simple or pincer-like;
variable in size and form, largest in
male.
Genitalia - see text.
Spiracles - two pairs on thorax and
eight pairs on abdomen.
Internal
Reproductive System.
Female - variable. Ovarioles in three
rows the length of oviduct, in a single
series, or five, eight, or 10-12; very
short or elongate.
Male - variable. Testes composed of a
pair of elongated follicles, a pair of
filiform coiled follicles, or a pair of
globular bodies, each with 16 short
follicles.
Vas deferens -_ slender. Ejaculatory
duct with one or two openings.
Some of the early ideas concerning the earwigs are: that they occasionally
enter the cars of sleeping human beings and even penetrate the brain; that the
forceps resemble to a remarkable degree the pincers used to puncture human
ears for the insertion of earrings; that the expanded wings of the earwigs resemble
somewhat the shape of the human ear. In view of the nocturnal crawling
habits of these creatures, which are always seeking small passages for concealment,
it seems likely that they might enter the human ear, especially where
they are abundant. and the natives not too particular about their habitations.
They are among the more ancient of insects, and fossil remains have been
found in the Lower Lias, the oldest division of the European Jurassic, at Aargau,
Switzerland; the Jurassic of eastern Siberia; the Tertiary, Oligocene, and Miocene
in general; and the Lower Miocene of Florissant, Colo. In the Tertiary,
where they are found most frequently, the greatest numbers belong to the single
genus Labiduromma Scudder, and differ little from present living forms.
As a natural group these insects are quite homogenous and are without striking
variations in either structure or habits.l The color is for the most Part
various shades of black and brown, although certain tropical species are brilliant.
Earwigs are nocturnal, terrestrial animals which seek refuge in moist, shady
places under stones, boards, bark of trees, and in piles of refuse or manure, as
well as in hollow stems of plants, cracks in the soil, and, in fact, anywhere secluded
from the light. They are generally omnivorous feeders. In the cooler
regions they appear to be mainly herbivorous, living for the most part on dead
or decaying vegetable matter but frequently eating all or parts of Jiving plants.
But in the tropics they are often carnivorous, and cannibalistic to a consider-
1 The ARIXENINA are quite different from the true earwigs and might appropriately be
placed in a separate order.