INJURIOUS AND BENEFICIAL INSECTS OF CALIFORNIA. 



191 



Life History.— Little is known relative to the life history of the 

 thread scale, but it is probably similar to that of the oyster-shell 

 scale or the purple scale. 



Nature of Work.— The species usually feeds upon the foliage, where 

 it often collects in large numbers. 



Distribution. — The insect occurs in the San Francisco Bay region 

 and in greenhouses throughout the State. 



Food Plants. — Coffee, jasmine, magnolia, Monstera, palmetto, fan 

 palm, palms and screw pine are common 

 hosts. 



Control.— Resin wash, miscible oils and 

 oil emulsions may be used to control this 

 scale. Young infested plants should be 

 dipped if possible. 



THE DATE PALM SCALE 



Parlatoria blanchardii (Targ. ) 10S 

 (Coccus blanchardii Targ.) 



(Fig. 167) 



Description.— The female scales are very 

 small, somewhat elongated in shape and 

 dark gray or almost black with white edges. 

 The length is about 1-18 inch. The body 

 beneath the scale is rose-colored. The male 

 scales are white and considerably smaller 

 than the females. 



Life History. — Like other scales, this 

 species collects in great colonies, and often 

 works much damage to the host plant. The 

 colonies are most destructive during the 

 summer months, as the females are more or 

 less dormant during the winter. Egg- 

 laying begins early in the spring and con- 

 tinues through the early summer at least. 

 Only a few eggs are laid by each female, 

 but there are so many of the latter that the 

 progeny is always tremendous. The eggs 

 are protected under the posterior portion of 

 the scale and as they hatch the young crawl 

 forth to seek suitable feeding places. The 

 males develop much quicker than do the females, and copulate imme- 

 diately before dying. There are probably several uneven generations 

 a year. 



Nature of Work.— The scale collects in great numbers upon the 

 stems and leaves of the date palms and their attacks are often so 

 severe as to kill the trees. The young offshoots become infested almost 

 as soon as they appear and are a ready means of distributing the pest. 



Fig. 167. — The date palm 

 scale. Parlatoria blanchardii 

 (Targ.), on palm leaf. En- 

 larged twice. ( Author's illus- 

 tration, Mo. Bui. Cal. Hort. 

 Com.) 



10S In Dr. G. Leonardi's work this name is spelled Parlatoria blanchardi (Targ.). 



