THE BARK-LICE. 



79 



species are hoppers, the hind legs being enlarged, while 

 many (except the plant and bark lice) have an ovipositor, 

 for inserting eggs in the twigs of plants. Many species 

 secrete, in numerous glands in the skin, a white waxy 

 powder which covers the body. 



We have always regarded, and still regard, the typical 

 Homoptera, such as Cicada, as a more highly specialized 

 insect than any of the Heteropterous Hemiptera; but in 

 treating of them in the pages of a book, and in deference 

 to the views of Hemipterists, we interpolate the sub-order 

 between the Pediculina and Heteroptera. 



Family Coccidae. The bark-lice or scale insects are so called from 

 the habits and shape of the females, which are wingless, with bodies 

 resembling scales. They insert their long slender beak into the bark 

 of trees or stems and leaves of plants, drawing in the sap, and when 



FIG. 64. Cochineal insect, 

 male; female, natural size 

 and enlarged. 



FIG. 65. Orange-scale insect, a, male; b, 

 female; d, its scale; c, another species. 



very numerous do much harm to the plant or tree. On the other 

 hand, the males have two wings and a pair of balancers, but no beak, 

 and take no food. The females lay their eggs beneath the end of 

 their bodies. While the eggs are generally fertilized, in species of 

 Lecanium and Aspidiotus, they develop without fertilization by the 

 males. Unlike the females, the males undergo a metamorphosis, the 

 larva? spinning a cocoon; the pupae remaining therein without moving 

 or taking food. While most of the species are injurious to vegetation, 

 the cochineal Coccus (Fig. 64) produces a carmine dye, and the manna 

 and lac insects by their punctures cause a flow of vegetable juices, 

 which, when dry, are a valuable article of merchandise. 



With us the most injurious species is the Apple bark-louse, Mytilas- 

 pis pomorum Douche, whose scales sometimes so abound on the bark 

 as to kill young trees; oranges are injured by M. gloverii (Pack., 

 Fig. 65), and the purple orange-scale, M. citricola (Pack.). Plants in 

 hot-houses are often injured by the " mealy bug." Coccus (Dactylopiiis 

 adonidum Linn.), which also occurs in gardens, as does Lecanium 

 hesperidum, which especially affects the orange. Pulvinaria in- 

 numerabilis (Rath von) injures the linden and soft maple. 



