LIBRARY

DERMAPTERA 186
ing and killing prey, and to a lesser extent in the folding and unfolding of the
wings. The females are oviparous, laying large numbers of smooth, oval eggs,
which in some species are white, in the damp soil, manure, refuse, or anywhere
that the insects occur in nature. In the temperate regions the eggs are often
laid in late winter or early spring and hatch soon after deposition. Maternal
care of the eggs and young by the females has been observed for many years.
Multiplication is often very rapid, and earwigs may become a serious nuisance
indoors and a pest in the garden. There are from four to six molts from the firstborn
to the adult. In cooler regions there is but one generation a year, while in
the tropics reproduction and development go on unabated.
The abdomen is well developed and is composed of nine distinct and two
indistinct segments in the male and seven distinct and two indistinct segments
in the female. In the former the first tergum is fused with the metathorax and
the 11th is represented by a small pygidium. In the latter the eighth and ninth
segments in front of the terminal segment are hidden by the seventh. These
terminal segments in certain forms are designated as opisthomeres. They comprise
a small horny plate projecting downwards from the 10th segment above
the anus, representing the supra-anal plate or pygidium, the metapygidium,
and the telson, which are much used in classification. The forceps are modified
cerci or uropods, as evidenced by the fact that in several species the immature
stages bear many-segmented cerci much longer than the body. These cerci are
reduced to a single pair of typical forceps with the last molt (Fig. 53). The
forceps occur in a wide variety of shapes and sizes and are conspicuous in all
species. They may be simple or armed with teeth and protuberances on the
inner surfaces which have some taxonomic value. If the 10th sternite is carefully
removed, it will be found to have on the anterior margin a manubrium, a
small membrane supported by a hardened band, which is of unknown use.
There is also exposed the male genital organ or penis which may be easily removed
and mounted for study, it being of great value in classification. The hidden
sternites, the paraprocts, and the opisthomeres are likewise exposed to
view and the latter may be removed and mounted on points or microscopic
slides for study. There are two pairs of spiracles on the thorax and seven pairs
on the abdomen (Westwood, 1839).
Earwigs and arixenids comprise a very small order of about 1,050 described
species and reach their maximum development in the tropics with gradually
decreasing numbers towards the cooler limits of the temperate regions.
KEY TO SUBORDERS
1. Compound eyes much reduced; inner margin of the mandibles densely
bristled; forceps feeble and hairy; body hairy; on bats or in bat
caves AR.IXENINA p. 137
blood was drawn, and Commander J. J. Walker had the same experience in New South Wales,
from the largest known earwig, Anisolabis (Titanolabis) clossea" (Burr, 1910).
P. Rau, in Tlte Jungle Bees and Wasps, 1933, has this to say about the Panama species,
Psalis americana Beauv.: "This earwig has a pair of forceps on the rear of the body which are
used with such astonishing efficiency that the creature is likely to gain its freedom whenever it
uses them."