BARK-LICE. 251 



threads, which are fastened, in a radiated manner, around 

 their bodies, to the bark, and serve to confine them securely 

 in their places. After becoming thus fixed they remain 

 apparently inanimate ; but under these hfeless scales the 

 transformation of the insect is conducted ; with this remark- 

 able difference, that in a few days the large ones contrive 

 to break up and throw off, in four or five flakes, their outer 

 scaly coats, and reappear in a very similar form to that 

 which they before had ; the smaller ones, on the contrary, 

 continue under their outer skins, which serve instead of co- 

 coons, and fi-om which they seem to shrink and detach them- 

 selves, and then become perfect pupte, the rudiments of 

 wings, antennae, feet, &c. being discoverable on raising the 

 shells. 



If we follow the progress of these small lice, which are 

 to produce the males, we shall see, in process of time, a pair 

 of threads and the tips of the wings protruding beneath the 

 shell at its lower elevated part, and through this little fissure 

 the perfect insect at length backs out. After the larger lice 

 have become fixed, and have thrown off their outer coats, 

 they enter upon the pupa or chrysalis state, which continues 

 for a longer or shorter period, according to the species. But 

 when they have become mature, they do not leave the skins 

 or shells covering their bodies, which continue flexible for 

 a time. These larger insects are the females, and are des-, 

 tined to remain immovable, and never change their place 

 after they have once become stationary. The male is ex- 

 ceedingly small in comparison to the female, and is provided 

 with only two wings, which are usually very large, and lie 

 flatly on the top of the body. 



After the insects have paired, the body of the female 

 increases in size, or becomes quite convex, for a time, and 

 ever afterwards remains without alteration ; but serves to 

 shelter the eggs which are to give birth to her fiiture off- 

 spring. These eggs, when matured, pass under the body 

 of the mother, and the latter by degrees shrinks more and 



