290 



INSECTS DESTRUCTIVE TO PLANTS. 



ALTHOUGH it be impossible to particularise every 

 species of insect which breed and prey on plants, a 

 few of the more common and noxious may be men- 

 tioned, in order to show how the health of plants is 

 injured, and their members distorted or destroyed by 

 their depredations. 



Coccus. This tribe of insects, of which the highly- 

 prized cochineal of commerce is the type, are found 

 infesting plants in hot- houses, as well as several of 

 our most useful fruit-trees cultivated in the open air. 

 The migratory white one, frequently seen on pine- 

 apple plants, is highly injurious by withdrawing the 

 juices and disfiguring the leaves, and still more when 

 they fix themselves on the bottom of the stem among 

 the roots. Both sexes are very minute when young ; 

 but the females, after impregnation, grow to nearly 

 a line in length, are then very sluggish, and probably 

 die soon after they have produced their young. 



The next species is the well-known brown scale, 

 so frequently seen on orange myrtle, and other plants, 

 whose leaves are of a firm texture. In early life they 

 are wanderers and invisible to the naked eye ; but 

 like the preceding, the females, after impregnation, 



