COLOUR- PRODUCING INSECTS. 55 



a little wax, colouring matter, and grease, and that 

 it exudes from the branches of Zizyphus jujuba and 

 other trees, after they have been pricked by the Coccus 

 lacca. It is collected from various trees and shrubs 

 in India, where it is very abundant, and has the 

 appearance of a concrete juice adhering to and 

 encircling the branches. Chevreul discovered that 

 its red colour was owed to carminium the principle 

 of the cochineal, and therefore its colour is certainly 

 produced by the insect Coccus. 



There are several varieties of this substance, 

 known in commerce as stick-lac, seed-lac, and shell- 

 lac. Stick-lac, when it is in its natural 

 state, adhering to the branches (Fig. 4) ; 

 seed-lac when separated, pulverized, and 

 the greater portion of colouring matter 

 extracted by water ; lump-lac, when 

 melted and made into cakes ; shell-lac, 

 when strained and formed into trans- 

 parent plates. 



Two other products are also brought 

 from India. They are chemical prepara- 

 tions for dyeing, called lac-lake and lac- 

 dye. 



In the latter country lac is used to 



FIG. 4. , J 



stick-lac, manufacture beads, rings, and other 

 ornaments. Mixed with sand, it is used to construct 

 grindstones. In this country it is used principally 



