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178 COLLEGE ENTOMOLOGY
laboratory at different times for closer observations, no males of this species
have been observed or collected. Ross has recently discovered that they reproduce
parthenogenetically.
If the silken webbing is tom asunder, the insects appear to be little disturbed
although they may feign death. But if personally molested, they react with
lightning rapidity and dart forwards or backwards with equal agility. They
offer no hostile resistance and avoid rather than court danger. Like termites,
they shun light and apparently leave the tunnels and coverways only at night,
yet they are active enough during the day if the sky is overcast and the temperature
mild or if their abodes are molested. Those who have observed certain
embiids state that the relatively large, somewhat cylindrical eggs, which
have a prominent operculum at one pole, are laid in the tunnels in small
groups uncovered or in a matrix of excrement and saliva and are covered with
one or more layers of silk web. The eggs are more or less cared for by the
parents, as in the case of termites and earwigs, but they are not transported
about. Little is known of the life histories, including particularly the numbers
of ecdyses and the life span. Spinning is acquired early and all forms including
the first instar diligently ply the art of lining the extensive runways. It appears
that both forelegs! are used and many threads are drawn simultaneously from
the numerous spinning hairs on each of the enlarged tarsal segments so that
the web is laid down with considerable rapidity.2 Most species are very dark
colored in the adult stage, some being almost black, and a few have a metallic
luster. Others are often pale in color, and the members of our local apterous
California species are pale tan or pinkish. Their food is thought to be wholly
vegetable, and that chiefly dead and decayed. Perhaps fungi play an important
part in the diet. Specimens have been confined in the laboratory for
months with nothing but dead vegetable debris for food. At times they feed
readily upon bits of fresh lettuce which they first enclose within their webs as
they consume it.
The mouth parts are similar to those of the ORTHOPTERA, with all
members well developed. The thorax is narrower than the head anteriorly and
gradually widens posteriorly. In the apterous forms the segments are longer
than wide but in the winged males they are wider. The legs are short and
stout to enable them to travel freely in the small tunnels. The first segment of
the fore tarsus is noticeably enlarged and bears the spinning organs. The
middle pair of legs is somewhat reduced. The femora of the hind legs are
greatly enlarged to accommodate the highly developed depressor muscles of the
tibire which probably motivate movement in reverse. The tarsi are threesegmented,
but the middle segment is very small in the forelegs. Two or
three sole bladders on the tarsal segments of the hind legs appear in some
species and are of value in classification. Wings occur only in the males of
1 The only other insects that use their fore tarsi for spinning silk are flies belonging to the
family EMPIDIDtE. See p. 776.
2 There has been some controversy in past years regarding the exact location of the spinning
organs since certain entomologists believed that the gloss