CHAPTER VI. 



INSECTS PBEYING UPON BABK-LICE. 



[Plate VI.] 



Numerous enemies prey upon Bark-lice in all their stages, and always 

 greatly reduce their numbers. Besides occasional enemies, such as the 

 sucking-bugs and other predatory insects, which are general feeders, 

 there are others which live almost or quite exclusively upon the Coccidse. 

 Some of these confine their attacks to particular kinds of Scale-insects. 

 Several very common beetles of the family Coccinellidce, the " Lady-birds," 

 are useful destroyers of Bark-lice. One of the smallest of this family, 

 Hyperaspidius coccidivorus, is found to colonize upon the trunks of orange 

 trees thickly infested with Chaff Scale, and entirely free them of the 

 pest. The young of a Lace-wing fly (Chrysopa) feeds upon the Bark-lice 

 in all stages, and frequently makes its case of scales torn from the bark 

 and often still containing living occupants. The Orange Basket- worm 

 (Platceceticns gloveri] has the same habit, and the caterpillars of at least 

 two moths are Bark-louse eaters. One of these (an unknown Tineid) 2 

 inhabits silken galleries, which it covers with half eaten fragments of 

 scales, and performs such efficient service that every scale in its path 

 is removed from the bark and suspended in the investing web. 



The most important external enemies of the Scale-insect are certain 

 mites, which are omnipresent upon trees infested with scale, and which 

 feed upon the eggs and young lice. They breed rapidly and lurk in 

 great numbers under old deserted scales, where their eggs are extremely 

 well protected from the action of insecticides. For this reason, when an 

 effective application has been made by spraying infested trees, the 

 trunks should not be scraped for some time after, but the dead scales 

 should be allowed to remain upon the bark for several weeks, in order 

 that the mites which they harbor may be given time to complete the 

 work of the remedy used. In this they may be confidently relied upon 

 as powerful auxiliaries. When large numbers of the scales have been 

 killed by spraying with oils, &c., the mites are often observed to in- 

 crease suddenly, as they are much less affected by the application than 

 the Scale-insects themselves. It seems probable that they feed upon 

 the dead and dying Coccids as well as upon the living, and the loosen- 

 ing of the scales and abundance of food at such times stimulates them 

 to rapid increase. They soon swarm in such numbers as completely to 

 exterminate the remnant of the Coccids left alive by the wash. 



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