198 INSECTS INJURIOUS TO VEGETATION. 



much groping about, in consequence of the provident care of the 

 parent flies, which leave their eggs in the very midst of the slug- 

 gish lice. Mr. Kirby says, that, on examining his currant-bushes, 

 which but a week before were infested by myriads of aphides, not 

 one was to be found ; but beneath each leaf were three or four 

 full-fed maggots, surrounded by heaps of the slain, the trophies of 

 their successful warfare. He also says that he has found it very , 

 easy to clear a plant or small tree of lice, by placing upon it sev- 

 eral larvae of Coccinella or Syrphi. 



3. Bark-lice. Coccida. 



The celebrated scarlet in grain, which has been employed in 

 Asia and the South of Europe, from the earliest ages, as a color- 

 ing material, was known to the Romans by the name of Coccus, 

 derived from a similar Greek word, and was, for a long time, sup- 

 posed to be a vegetable production, or grain, as indeed its name 

 implies. At length it was ascertained that this valuable dye was 

 an insect, and others agreeing with it in habits, and some also in 

 properties, having been discovered, Linnaeus retained them all un- 

 der the same name. Hence in the genus Coccus are included not 

 only the Thola of the Phoenicians and Jews, the Kermes of the 

 Arabians, or the Coccus of the Greeks and Romans, but the 

 scarlet grain of Poland, and the still more valuable Cochenille of 

 Mexico, together with various kinds of bark-lice, agreeing with 

 the former in habits and structure. These insects vary very 

 much in form ; some of them are oval and slightly convex scales, 

 and others have the shape of a muscle ; some are quite convex, 

 and either formed like a boat turned bottom upwards, or are kid- 

 ney shaped, or globular. They live mostly on the bark of the 

 stems of plants, some however, are habitually found upon leaves, 

 and some on roots. In the early state, the head is completely 

 withdrawn beneath the shell of the body and concealed, the beak 

 or sucker seems to issue from the breast, and the legs are very 

 short and not visible from above. The females undergo only a 

 partial transformation, or rather scarcely any other change than 

 that of an increase in size, which, in some species indeed, is enor- 

 mous, compared with the previous condition of the insect ; but 

 the males pass through a complete transformation before arriving 



