THE INSECT WORLD. 



265 



americana^ and certain varieties of grapes are occasionally in- 

 jured by its larva. Feeding in colonies, as it does, the insect is 

 easily checked by local applications of the arsenites. 



Fig. 286. 



Grape-leaf on which larvae of Harrisma mnericana are feeding. 



We now enter into a series of species the caterpillars of which 

 are known as " woolly bears," from the fact that they are all 

 clothed with long hair. In some cases this hair is so dense that 

 the body of the caterpillar itself cannot be seen at all, and all 

 these are of the Arctiid series. They spin a small quantity of 

 silk only, and use the hair with which they are clothed in con- 

 junction with it to form the cocoon. Under the microscope it 

 may be seen that it is furnished with small spurs or branches, by 

 means of which the insect is able to produce a felt-like material, 

 needing only a small quantity of silk to hold it together in a 

 tissue sufficiently firm for its purpose. Perhaps the majority of 

 the caterpillars of this series feed upon low plants, and frequently 

 it does not matter much what. Plantain seems to be a common 

 food for many species, but they eat grasses as well, and, indeed, 

 almost anything. They are often found in gardens attacking 

 lettuce and cabbage, and on cabbages they are sometimes trouble- 

 some in the field. Some are almost white or yellowish, and vary 



