Ii8 AN ECONOMIC ENTOMOLOGY. 



In our treatment of these insects we must either apply exceed- 

 ingly caustic winter washes, to corrode the scale and allow the 

 eggs to be washed out by rain or destroyed by other climatic 

 influences, or we must apply contact insecticides when the eggs 

 hatch or the larvae emerge from beneath the scales. 



Some of our destructive species belong to the genus Aspidiotus, 

 and these have the scale nearly circular in outline, with the rem- 

 nants of the cast larval skins showing through at or near the 

 middle and forming a sort of nipple-like prominence. The male 

 scales are decidedly smaller than those of the female, and some- 

 what more oval or oblong. The ' ' red scales' ' of the orange in 

 California and in Florida belong to this genus ; but perhaps the 

 most troublesome of all is the A. peryiiciosns , or San Jose scale. 

 As this species is now widely distributed and very injurious where 

 it occurs, its life history may be given in some detail. 



The insect winters on the infested trees in the larval state, and 

 usually about half grown, both sexes being found. Males mature 

 soon after spring opens, — in the latitude of Philadelphia, about 

 the middle of May, but depending somewhat upon the season. 

 Toward the end of that month the females become fully devel- 

 oped, and begin to bring forth living young. That is to say, the 

 species is viviparous, and produces no eggs. The larvae do not 

 differ essentially from those of other scales, and fix in from twelve 

 to thirty-six hours, depending somewhat upon circumstances. 

 At that time a thin white pellicle forms, which soon turns yellow, 

 and a little later becomes gray around the edges. The insect is 

 then a fixture, and continues its growth much as previously 

 described, but reaches the adult condition, and is ready to repro- 

 duce, in a little more than a month. This short period enables 

 it to mature several broods, and during the entire summer, and 

 until late fall, reproduction continues, — the broods becoming 

 mixed, and all stages being present continuously upon the plants 

 soon after summer opens. With such a life history the insect is 

 exceedingly difficult to control, and practically we are reduced to 

 winter work, as will be hereafter pointed out. The scale infests 

 all the usual deciduous fruit-trees, roses, currants, gooseberries, 

 — in fact the entire order Rosacecs, and occasionally occurs on 

 chestnut, walnut, and elm. It is probable that yet other plants 

 are subject to infestation, and this omnivorous habit and the 



