INSECT ENEMIES OF CITRUS FRUITS. 



11 



generally so destructive as to require extended efforts for their 

 control are the purple scale (Lepidosaphes hechii Newm.), the red 

 scale {GhrysompTialus aurantii Mask.), and the black scale {Saissetia 

 olex Bern.). The yellow scale { ChrysompJialus citrinus Coq.), con- 

 sidered a variety of the red scale, is much less destructive generall}^, 

 though sufficiently troublesome in some localities to be considered a 

 pest of primary importance. Other scale-insects attacking citrus 

 trees, which are so perfectly held in control by their natural enemies 

 and other causes as seldom to become very destructive, are the soft 

 brown scale ( Coccus hesperidum L.), the hemispherical scale (Saissetia 

 hemisphserica. Targ.), the oleander scale (Aspidiotus Jiederse Val.), 



Fig. 2.— Leaves and branch of orange infested with purple scale {Lepidosaphes beckii). (Original.) 



and the cottony cushion scale {Icerya purcTiasi Mask.). Mealy bugs 

 (Pseudococcus spp.) are quite generally prevalent. 



The most important pests other than scale-insects are to be found 

 among the mites, of which the rust mite of the orange or silver mite 

 of the lemon (Phyllocoptes oleivorus Ashm.) and the citrus red spider 

 ( Tetranychus mytilaspidis Riley) are highly injurious. The orange 

 aphis (Aphis gossypii Glov.) becomes very numerous during some 

 seasons but is soon attacked by its natural enemies and held in con- 

 trol. A species of thrips worked quite extensively in some localities 

 on ripe oranges during the first months of 1908, removing the coloring 

 matter from beneath the epidermis, thus giving to the fmit a spotted 

 appearance which lowered its market grade. 



The purple scale (figs. 2 and 3) appears to prefer the more moist 

 regions in the vicinity of the ocean. It is found in Santa Barbara 



