BARK-LICE. ^55 



being broad at the hinder extremity, but tapering towards the 

 other, which is surmounted by a little oval brownish scale. 

 The small ones, which are not much more than half the 

 length of the others, are of a very long oval shape, or 

 almost four-sided, with the ends rounded ; and one extrem- 

 ity is covered by a minute oval dark-colored scale. These 

 little shell-like bodies are clustered together in great num- 

 bers, are of a white color and membranous texture, and 

 serve as cocoons to shelter the insects while they are under- 

 going their transformations. The large ones are the pupa- 

 cases or cocoons of the female, beneath which the ego's are 

 laid; and the small ones are the cases of the males, and difPer 

 from those of the females not only in size and shape, but 

 also in being of a purer white color, and in having an 

 elevated ridge passing down the middle. The minute oval 

 dark-colored scales on one of the ends of these white cases 

 are the skins of the lice while they were in the young or 

 larva state, and the white shells are probably formed in the 

 same way as the down which exudes from the bodies of other 

 bark-lice, but which in these assumes a regular shape, vary- 

 ing according to the sex, and becoming membranous after 

 it is formed. Not having seen these insects in a living state, 

 I have not been able to trace their progress, and must there- 

 fore refer to Caiman's memoir above mentioned, for such 

 particulars as tend to illustrate the remaining history of this 

 species. 



The body of the female insect, which is covered and con- 

 cealed by the outer case above described, is minute, of an 

 oval form, wrinkled at the sides, flattened above, and of a 

 reddish color. By means of her beak, which is constantly 

 thrust into the bark, she imbibes the sap, by which she is 

 nourished ; she undergoes no change, and never emerges 

 from her habitation. The male becomes a chrysalis or pupa, 

 and about the middle of July completes its transformations, 

 makes its escape from its case, which it leaves at the hinder 

 extremity, and the wings with which it is provided are re- 

 versed over its head during the operation, and are the last 



