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. Desoria glacialis (greatly enlarged). 



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 antennae 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-fish (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 011 

 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. 



C. J. GAHAN. 



