286 OBSERVATIONS ON INSECTS. 



colour, and about two lines in length. There were 

 also some small brown coccoons among the roots, 

 here and there, likewise about two lines in length, 

 which I kept, in the hope of their turning to the 

 perfect state, but without success. Probably these 

 were the larva and pupa respectively of some dip- 

 terous insect, which keeps the root aphis in check. 

 When once, however, the nuisance occasioned by 

 this last parasite shews itself in a garden, the only 

 effectual way of getting entirely rid of it is imme- 

 diately to pull up all the diseased plants and burn 

 them. 



LICE.* 



ALMOST every animal, as well as bird (it is well 

 known), has its peculiar louse. It is, however, 

 singular, and contrary to what one might have ex- 

 pected, that the size of the parasite is by no means, 

 in all cases, proportioned to the size of the animal it 

 infests. The louse of the swine f is as large as the 



wise a species of Eriosoma, but differed from the E. lactuca in 

 having the abdomen shorter and broader, (or more approaching to 

 round than oblong,) and in being more sluggish in habit, hardly 

 attempting to move when taken from the plant : it also kept more 

 on the surface of the ground, at the bottom of the leaves and 

 stems, than under ground ; though many might be noticed at the 

 roots themselves. 



Reaumur has given a list of plants, at the roots of which he 

 had found Aphides, but the lettuce is not included. Hist, des Ins. 

 (12mo. ed. Amst. 1738,) torn. iii. 2nd part, p. 80. 



* Anoplura of Leach. 



t Hamatopinus suis, Denny; Anopl. Brit. pi. xxv. f. 2, 



