242 HEMIPTERA-HOMOPTERA. 



room for air, and clean, will prevent any serious damage from 

 this pest All rough bark should be cleared off, mosses and 

 lichen destroyed by the washes mentioned in the Appendix, 

 and the tree trunks painted annually with some of the numerous 

 preparations of lime, soft-soap, and paraffin. 



Numerous other plant-lice attack crops and fruit, among 

 which we may mention the Corn Aphis {Siphonophora granarid) ; 

 the Cabbage Louse {Aphis hrassicce), which crinkles up the 

 cabbage leaves, forming a mealy mass of lice ; the Plum Louse 

 (A. 2yruni) (fig. 122), curling up the leaves of the plum; the 

 Cherry Louse (Myzus c&rasi) (fig. 121), which collect on the 

 shoots of cherries, forming black groups and discolouring the 

 fruit with their excrement ; the Currant Aphides {Ehopalod- 

 pJium ribis), &c. All can be destroyed by the same washes, 

 and need no further comment here. {Vide Appendix IL) 



Scale Insects (CoooiDiB). 



These Hemiptera are peculiar in many respects. The females 



are always apterous degenerate creatures, devoid of legs and 



antennas, and generally lie hidden under 



y'^r^^ ■■'^sr\ ^ scale-like mass, formed by the excre- 



i/^-M. ^^^^\ tioiis of the insect and the cast skins 



li'*'-~^iv''t'^^ \ °^ ^^^ larva (exuvise). They have a 



vfeV^^^^^" ^ J ^^•'"y ^°^S thread-like beak, which is 



IP^^^^^^ft^^ thrust into the bark, leaf, or fruit of 



//// iBi^lJ^^ I the plant, these insects being fixed 



^W^ during the whole of their life, after the 



*■■ larval stage is passed, in the female 



'aoALEi^CAte Howrrd.r sex. The males (fig. 124, i) are winged, 



generally having one pair only, the 



second pair being hook-like processes. The male scale (vi) is 



quite different from the female scale (v) in form. Some 



Coccids, such as the Mealy bugs, form no scale, but are then 



