INJURIOUS AND BENEFICIAL INSECTS OF CALIFORNIA. 179 



Nature of Work.— All stages feed upon the bark and in a few eases 

 have killed the trees. 



Distribution. — The distribution of this scale in California is not 

 well known. It does not seem to have made any considerable head- 

 way in the State. 



Food Plants.— Like many other members of the genus Aspidiotus, 

 this coccid is a general feeder attacking alder, apple, apricot, aspen, 

 birch, cherry, currant, date palm, hawthorn, heather, horse-chestnut, 

 linden, maple, oak, peach, pear, plum, prune and poplar. 



Control. — Control measures as recommended for the San Jose scale 

 may be used in combatting this pest also. 



Natural Enemies.— The two-stabbed (Chilocorus bivulnerus Muls.) 

 and other ladybird beetles feed upon all stages of the European fruit- 

 tree scale. 



THE PERNICIOUS OR SAN JOSE SCALE 



Aspidiotus pernicinsus Comstock 

 (Figs. 157, 158) 



Description. — The female scales are nearly circular, slightly con- 

 vex, quite dark when young, light gray when fully matured and from 

 1-25 to yV inch in diameter. The exuviae are central or nearly so and 

 form yellow or dark nipples. The bodies are oval and light yellow. 

 The male scales are much smaller than those of the female, twice as 

 long, as wide and very dark gray or black. The adult males are pink 

 and exceedingly small and delicate. 



Life History. — The winter is spent in a half -grown condition, when 

 the scales of the females are black. Maturity is reached in spring and 

 early summer, the young being born at this time. They settle upon 

 the leaves, fruit, limbs and trunks of the trees where they may be 

 massed in great numbers. There are from one to three uneven broods 

 a year. 



Nature of Work. — This species attacks the trunk, large and small 

 limbs, leaves and fruit, producing a very characteristic red or purple 

 stain which discolors the tissues. On the fruit and just beneath the 

 bark the discolorations are very noticeable (Fig. 158). Limbs and 

 entire trees are often killed by the attacks and fruit is rendered worth- 

 less for market because of the reddish blotches produced upon the 

 skin. 



Distribution.— The San Jose scale is a very common pest, occurring 

 throughout the entire State and country. 



Food Plants.— Acacia, Actinidia, Akebia, . alder, almond, flowering 

 almond, apple, crab apple, apricot, arborvitge, ash, American mountain 

 ash. European mountain ash, beech, birch, false bittersweet, blackberry, 

 buttonbush, buckthorn, catalpa, Ceanothus, cherry, sand cherry, chest- 

 nut, black chokeberry, chokecherry, Cercidiphyllwn japonicum, coton- 

 easter, currant, dogwood, elder, elm, eucalyptus, Euonymus. fig, goose- 

 berry, grape, hackberry, hawthorn, Hibiscus, honeysuckle, hop-tree, 



