INSECTS. PODURID^E. 323 



of the cricket offer many curious points for microscopic examination. 

 The cricket has two wings, which are covered with wing-cases of a 

 leathery consistency, near the base 

 of which is a horny ridge having 

 transverse furrows, exactly re- 

 sembling a rasp or file ; this the 

 cricket rubs against its body with fi ^ 154 ' The Cricket ' 



a very brisk motion, whereby it produces its sound. It has been 

 remarked that the chirp becomes louder in proportion as the heat 

 increases ; and it is extremely difficult to silence the cricket in any way 

 but by putting out the fire near which the little animal is chirping. 



In the order Thysanoura there is a remarkable diversity of struc- 

 ture. They undergo no metamorphosis, and have no wings. The 

 order contains two families, the Podu- 

 ridce, or /Spring-tails, and the Lepismidce. 

 In the former, the caudal appendage 

 has the form of a forked tail {Podura, 

 fig. 155), which is bent under the animal 



when not in use, and by its sudden ex- % 155 PoduraplumJ)ea . 

 tension causes the animal to spring, often The small circle encloses the insect 

 to a great distance in comparison with of life size. 



its size. The body is covered with numerous minute scales, often of .a 

 beautiful silvery or pearly lustre, and curiously striated. Some species 

 may be found jumping about on the surface of the water, whilst others 

 are met with in profusion upon snow and ice. 



The Lepismidce have a spindle-shaped body, usually covered with 

 silvery scales, and furnished along the sides of the abdomen with a 

 series of appendages or false feet, besides several long-jointed, bristle- 

 like organs at its extremity. The head is concealed under the pro- 

 thorax the eyes are usually compound, and frequently occupy the 

 whole of the head. The antennae are very long, and composed of 

 numerous joints ; and the maxillary palpi, which consist of from five 

 to seven joints, are very conspicuous. These insects generally inhabit 

 moist places. The most common species, Lepisma saccliarina, is fre- 

 quently found about houses, especially in sash-frames, or old sugar- 

 casks, from which it derives its name. The scales from these little 

 insects have always been favourite objects with microscopists, and are 

 generally used to test the power of penetration and definition of the 

 instrument itself. 



Podura plumbea, or Lead-colour Springtail, are usually found in 

 wine-cellars, amongst the sawdust, leaping about like fleas, and are 



