CH. XX.] HISTORY OF THE FLEA. 279 



of their bodies, which were exposed in certain sit- 

 uations where the thorax had been injured ; they 

 would not, however, attack uninjured flies. 



On the 9th of September some of these larvae 

 (which burst forth on the 28th of the preceding 

 month, from eggs deposited on the 23d) commenced 

 weaving their cocoons. Before taking this step, 

 however, they entirely voided the remains of their 

 undigested food, as is the practice with the majority 

 of larvae, after which they appeared quite white and 

 transparent. 



Rosel, however, observed, that while some of the 

 larvae incased themselves in a cocoon, others under- 

 went their transformations naked and without cov- 

 ering. The cocoon which they weave is of a silky 

 texture, and of an ellipsoid form, of a white colour 

 within and grayish externally, and often covered 

 with powder ; they are generally affixed to the sur- 

 rounding objects. The pupa bears great resem-! 

 blance to the perfect insects, with the diff"erence only 

 of the legs being folded closely upon the belly, and 

 the insect itself being covered with a thin pellicle, 

 the eggs being enclosed in distinct cases. Of course, 

 at this period, the insect is quite inactive. The col- 

 our of the pupa is at first a dirty white, but it after- 

 ward assumes the teint of the perfect insect. 



According to some authors, however, those larvae 

 which are not hatched from the eggs until the end 

 of the summer, pass the winter in that form. The 

 period of the duration of the pupa state varies from 

 eleven to sixteen days, at the expiration of which 

 the insect sheds the thin pellicle which had pre- 

 viously enclosed it, and appears in its perfect and 

 active form. 



And now commence those annoying attacks upon 

 our persons, from which none are exempt, and against 

 which various remedies have been proposed; on 

 which subject the following pleasant piece of satire, 

 by Poor Humphrey, will be read with a smile. 



