HOMOPTERA 



441 



or shellac is prepared, is a resinous substance excreted by this species, 

 which lives on the young branches of many tropical trees, most of 

 which belong to the genus Ficus, the figs. 



In the past, several coccids have been important as coloring agents. 

 The bodies of the lac-insects, which are obtained from stick-lac in the 

 manufacture of shellac, are the source of lac-dye. Another coccid, 

 Kermes Uicis, which lives on a species of oak in southern Europe, 

 has been used as a dye from very early times. And the well-known 



Pig. 512. — Chionaspis furfura: 7, scales on pear, natural size; /o, scale of male, 

 lb, adult male, ic, scale of female, enlarged. 



cochineal is composed of the dried bodies of a coccid, Coccus cacti, 

 which lives on various species of cactus. Recently these dyes have 

 been largely supplanted by those obtained from coal-tar. 



China-wax is also produced by a coccid. It is the excretion of an 

 insect known as pe-la, Ericerus pe-la, and was formerly much used in 

 China in themaniifacture of candles, before the introduction of parafiin. 



In the adult state, the two sexes of coccids differ greatly in form. 

 The males are usually winged (Fig. 512); in a few species they 



