LIBRARY

THYSANURA 67
complete segments, and the 11th segment is often modified into the median
caudal filament. There is a pair of styli and one or two pairs of eversible sacs
on a variable number of abdominal sternites. The cerci, often consisting of 50
or more similar segments, arise from the 10th segment.
Internal anatomy. - The digestive tract consists of a large or small gizzard
and a tube, either straight or with a single convolution in the hind intestine. Enteric
creca and salivary glands are present. Malpighian tubules are well developed
and consist of four to eight in the lepismids and 12 to 20 in the machilids.
There are normally two pairs of thoracic and seven or eight pairs of
abdominal spiracles and three thoracic and eight abdominal ganglia.
The habitat of these insects is quite variable. Perhaps the majority of the
species prefer damp places under leaves, debris, bark; in rotten wood, mosses,
lichens; on stones and trunks and limbs of trees; and in the nests of ants and
termites. A great many species, however, are found in comparatively dry, hot
places on the surface of sun-baked soil; among dry leaves and grasses; on warm
exposed rocks, in dry hollow logs, caves, stumps, and other natural shelters;
and in buildings, particularly in the basements, kitchens, and around stoves,
ovens, furnaces, and fireplaces. They are both diurnal and nocturnal; and are
somewhat omnivorous in their feeding habits. Most of them are vegetarians
that eat dry or decaying vegetation, fungi, lichens, mosses, and similar plant
materials. House-inhabiting forms feed on cereals, pastes, glues, and paper, as
well as starched clothing and sized silks and rayons. They may rarely eat woollen
goods and other animal products.
Little is known about their biology, They are apparently largely oviparous.
depositing their eggs in cracks and crevices out of sight. There are six or more
instars, and under favorable conditions of the tropics maturity is reached in less
than a year while in the temperate regions two or more years are required to
complete a generation.
KEY TO FAMILIES
1. Compound eyes large contiguous or approximate; two ocelli present;
styli usually present on the middle and hind coxre; abdominal styli
on sternites 2-9; tarsi three-segmented. MACHILIDlE
2. Compound eyes small and widely separated, or absent; ocelli absent;
1tyli absent. on coxre; abdominal styli on sternites 7-9 or 8-9; tarsi
chree- or four-segmented LEPISMIDlE p. 69
Family MACHILID}E Grassi 1888 (Ma-chil'i-dre, derivation obscure), Machi·
lids.
The members of this family are among the largest in the order, averaging
from 10-12 mm. in length, and are characterized by their somewhat cylindrical
scaly bodies which are widest through the thoracic region, the long antennre,
and the long caudal cerci and :Lilaments; the latter are often longer than the
oody. The compound eyes, which are well developed in this family, are large,