SCALE INSECTS. 



243 



covered with a quantity of mealy powder and wool. During 

 winter most of our outdoor scales are in the egg state ; the 

 ova are minute dust-like bodies found amongst a woolly mass 

 under the scale. In warmer and tropical climates scales hreed 

 all the year roimd, and so they do in hothouses in this country. 

 The young scale insects are active six-legged larvse (iv), which 

 wander about for a time and then settle down and form a small 

 scale, gradually increasing in size. If this larva is going to be- 



FlG. 124. — Male San Jos^ and Mussel scale. 



i, Male San Jose scale ; ii, larva of same ; ill, female scale ; iv, Larva of mussel scale ; 

 V, female mussel scale ; vi, male mussel scale, (i, ii, iii after Marlatt and Howard.) 



come a female, as it moults it loses its legs, antennse,, &c., and 

 degenerates into a sedentary apodal creature. But if the larva 

 is going to become a male, it enters a propupal and ])upal stage, 

 a new set of legs, &c., being formed, and wings appear as 

 bud-like outgrowths. They are very numerous and destructive 

 in warm climates, where fruit-trees are encrusted with them. 

 At least 1000 species have been catalogued by Mr Cockerell in 

 his recent check-list. Perhaps the most destructive is the San 

 Jos6 scale (^Aspidiotus perniciosus) (fig. 1 24, i, ii, iii), which 



