PAEASITA. 



181 



they run with great swiftness. Many species of these 

 insects lurk in the chinks of window-sashes that are 

 seldom opened, or they hide under wet planks and in 

 cellars. 



The Spring-tails (Podura) have their tail terminated 

 by two stiff spines, which are usually bent under the body. 

 By suddenly extending this apjjaratus, which acts as a 

 sjjring, the insect leaps into the air like a skip-jack, and 

 falls upon its back. The Podui'^e are foimd imder the 

 bark of trees, or sometimes on the surface of stagnant 

 water, or even of snow. They are generally congregated 

 together in considerable numbers, and have very much 

 the appearance of grains of gunpowder. 



Okdek Paeasita. 



The Parasita are wingless insects that do not 

 undergo metamorphoses, 

 and whose abdomen is 

 without any terminal ap- 

 pendage (Fig. 142). Their 

 mouth is adapted for suc- 

 tion, their body is flat- 

 tened, and, as their name 

 indicates, they live upon 

 other animals. They, 

 however, are only met 

 with in mammals and 

 birds. They are gene- 

 rally known bv the name 

 of ^ 



Lice (Pediciihs) and Ticks 

 [Bicinus). The latter, with 

 the exception of the Dog- 

 tick, only infest birds. 

 These insects by means of 

 tv\'o opposite claws, "^-ith 

 which their feet are armed, 

 cling to the hairs of quadrupeds and the feathers of 

 birds, in which situation they pass their lives, and some- 

 times multiply very rapidly. They fasten their eggs, 



Fig. 142. — louse. 



