136 AN INTRODUCTION TO ^GY. 



Dui 3, much attention h.is hern paid to devising 



method The insecticides which are now 



d are alkaline washes and k< mul>ion. (J 



Chapter \i\ 



>t usetul inse - ;1 ^t () this family. Several sp 



furnish dye-stutis. The best known <>f these is (\'>t't'HS <v/Y//, the 

 dried 1) I which are known as ( ' -chineal. The .stick l.u 



vom which shell-lac or shellac is prepared, is a resinous 

 sul>~- xcreted by one of the iirtcria ICu'ca, which 



lives on the young branches of several tro])ical 1 \nd the 



>f this insect, \\hich are obtained from the stick lac. furnish 

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

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

 of an insect known as IV-la, Kriccrus pc-la. In fact, many species of 

 this family excrete wax in considerable quantities. I have found 

 thn - 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 tl 

 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 uf a scale composed in part of moulted skins. 



15. Body of female usually remaining distinctly segmented. 

 'lM*f*r\ and retaining the power of motion till maturity: -me- 



time>. i : lee< mirs more or Ir-s globular and ; 



but in all cases the labium is eornpo- 

 nn-nts. and : no anal pl.ites. (Fig. IJI..//M The 



abdomen usually ends in a pair of lobes, each funi: 



with one or more bristles (Plate IV. Fig. i<-j. 



i. ( 



\\\\, 1 1< idy ( >f female (hanging much in form during devel >|>- 

 ment, becoming or IIX.K -'.obular. with 



the segmentation absent or indistinctly indicated. The 

 individuals usually In-con,. , the plant upon which 



pi'ates. Kcd ' they liv<-; sometimes they are enclosed in a coverin 



wax. In all < a-es the labium is composed of a single 



t tiiealii!. ial in the adult female ie 



gular pla 2 l.i 



* The characters given here for di " I.ccani: 



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



