THYSANOPTERA. 
203 
abdomen has at most but six segments and very often only three. The forked tail, 
which is attached to one of the hinder segments, is usually turned forwards and held 
in position under the body; when released, it springs back, striking the surface of 
support, and causes the insect to bound up into the air. These little insects are to 
be found commonly enough under flower-pots, leaves, and stones, or under the 
bark of trees and in other such situations. They may sometimes be seen collected 
together in great numbers, and spread over the surface of the ground like a layer 
of powder. Some species, such as Podura aquatica, may frequently be seen floating 
in patches on pools of water, and by striking 
their tails against the surface of the water, they can 
spring up into the air just as readily as others do 
from the ground. Desoria glacialis is an inter¬ 
esting species, found in Alpine regions, where it is 
often to be met with on the surface of the ice. 
The bristle-tails (Thysanura proper) form but a 
small number of genera, some of which are very remarkable in having a series of 
small rudimentary legs on each side of the abdomen in addition to the ordinary six 
legs borne by the thorax. In all the genera the antennas are formed of a large 
number of joints; and the abdomen shows ten distinct segments, and, except in the 
genus Japyx, carries at the end two or three long jointed tails. Japyx has instead 
a pair of short pincers like an earwig. The little silver-fisli ( Lepisma saccharina ) 
is one of the best known insects belonging to this suborder. Found very often in 
damp corners in houses, among old books or papers, it may be recognised by the 
silvery scales covering its body, and by its three bristle-like tails, of which the 
middle one is the longest. It feeds on the paste in the binding of books, and on 
sugary and starchy substances generally, though it is credited also with eating 
paper and linen. Thermophila furnorum is a species which lives in bakehouses, 
where, as its name implies, it is often found in the ovens. 
Machilis is one of the genera in which the abdomen is provided with rudi¬ 
mentary legs in the form of small cylindrical appendages, each of which is 
accompanied by two small protrusible sac-like organs. An appendage similar 
to those on the abdomen is attached to each of the coxae of the two hinder pairs 
of legs. The body, covered over with scales, is arched up in the middle, as in 
Lepisma, and carries three tails. The eyes are large and faceted ; and the palpi 
are long, those of the maxillae looking like a second pair of antennae. Two species 
of this genus are found in Great Britain; one being common about rocks at the 
seaside, while the other is to be met with under stones in different parts of the 
country. Campodea staphylinus, the last insect we have to mention, is a pale, 
soft-bodied little creature, which is common almost everywhere under stones and 
in loose garden soil. It runs actively, and has two very long tails which it sticks 
up in the air or turns forward over its body. It has no eyes; the antennae are 
shorter than the tails and of equal thickness throughout; and the abdomen has 
seven pairs of rudimentary appendages. 
Desoria glacialis (greatly enlarged). 
C. J. GAHAN. 
