136 AN INTRODUCTION TO ENTOMOLOGY. 



During recent years, much attention has been paid to devising 

 methods of destroying these pests. The insecticides which are now 

 most widely used are alkaline washes and kerosene emulsion. (See 

 Chapter XIV.) 



A number of useful insects belong to this family. Several species 

 furnish dye-stuffs. The best known of these is Coccus cacti, the 

 dried bodies of which are known as Cochineal. The stick lac of 

 commerce, from which shell-lac or shellac is prepared, is a resinous 

 substance excreted by one of the Coccinae, Carteria lacca, which 

 lives on the young branches of several tropical trees. And the 

 bodies of this insect, which are obtained from the stick lac, furnish 

 the coloring agent known as lac dye. China wax is another sub- 

 stance for which we are indebted to this family. It is the excretion 

 of an insect known as Pe-la, Ericerus pe-la. In fact, many species of 

 this family excrete wax in considerable quantities. I have found 

 three species in this country which, if they can be easily cultivated, 

 produce wax in sufficient quantities to be of economic importance. 



The family comprises four sub-families. One of these includes 

 species that live in galls, and is confined to Australia. The three 

 sub-families which are represented in our fauna can be separated by 

 the following table : * 



A. Body either naked or clothed with a secretion ; the clothing, however, not 

 in the form of a scale composed in part of moulted skins. 



B. Body of female usually remaining distinctly segmented, 

 and retaining the power of motion till maturity; some- 

 times, however, it becomes more or less globular and fixed, 

 but in all cases the labium is composed of several seg- 

 ments, and there are no anal plates. (Fig. 121, ap^) The 

 abdomen usually ends in a pair of lobes, each furnished 

 with one or more bristles (Plate IV. Fig. le). 



i. COGGING. 



BB. Body of female changing much in form during develop- 

 ment, becoming scale-like or more or less globular, with 

 the segmentation absent or indistinctly indicated. The 

 FIG. m.Ltca- individuals usually become fixed to the plant upon which 

 "A anal pUtes rRed ' they live ; sometimes they are enclosed in a covering of 

 wax. In all cases the labium is composed of a single seg- 

 ment ; the caudal opening of the alimentary canal in the adult female is covered 

 by a pair of subtriangular plates (Fig. 121, ap), 2 LECANINJE. 



^ * The characters given here for distinguishing the Lecanince and Coccinae are 

 merely provisional, as these groups are not yet well known. 



