RATA0ES OF THE ARMORED SCALES. 41 



The Long Scale is the most destructive, while it is the most readily de- 

 stroyed. Few if any localities in the State are free from its presence. 



The Purple Scale, being stouter and thicker than the Long Scale, is 

 more difficult to kill. It is not'less injurious to the trees which it infests, 

 but is less widely distributed. 



The Chaff Scale is hardly less common than the Long Scale, and is very 

 frequently associated with it. Of the three it is decidedly the most 

 difficult to exterminate, owing, in part at least, to its habit of piling or 

 lapping one over the other. Except upon very young trees it seldom 

 does permanent injury, and is much less to be feared than the other 

 two species. Its thinner scale renders it liable to the attacks of enemies 

 to a greater extent than the Mytilaspis scales, and they sometimes cause 

 its complete disappearance from a tree. 



A fourth scale of this group, Aspidiotus, ficus Ashtn. has been ^men- 

 tioned as recently introduced, and there are still others awaiting im- 

 portation from California and elsewhere. 



Afjencibs ivliick assist their Distribution. During the migratory age the 

 restless habit of the young Bark-lice impels them to crawl actively 

 about, turning aside for no obstacles, but mounting every object met 

 with in their path. The instinct of self-protection being entirely want- 

 ing in these degraded creatures, they make no distinction between dead 

 and living objects, and crawl without hesitation upon the bodies of 

 other and larger insects. The latter, impelled by the annoying presence 

 of the intruders, fly away, bearing with them the scale Iarva3, and thus 

 assist in distributing them upon surrounding plants. 



Some insects, however, do not notice, or at least do not resent, the 

 liberties taken by the crawling lice. 



Thus the Lady-bird beetles (Coccinellidre) are frequently seen quietly 

 feeding while several young Bark-lice, evidently attracted by their 

 shining backs, are coursing in all directions over their bodies. It can- 

 not be doubted that even these enemies of the Scale-insect bear with 

 them in their flights this seed of the destroyer and scatter the pest from 

 tree to tree. Doubtless very many flying insects, and also birds, with 

 their sweeping tail-feathers, aid in disseminating Scale-insects. 



But spiders, more than any other animals, must be considered effi- 

 cient instruments in this inischiavous work. Not only do they trans- 

 port the lice and it is an observed fact that the movements of the latter 

 upon their hairy backs do not incommode the spiders but they also 

 harbor them under their webs in folded leaves, etc., where, safe from 

 the attacks of parasites and enemies, they increase and multiply inor- 

 dinately. 



The nest web of a spider will most frequently be found the starting 

 point from which the lice swarm forth as from a hive and cover the 

 surrounding parts. Other webs, at a distance from the infected one, 

 will be occupied in time, but only as the tide of scales reaches their 

 vicinity, for it is not the habit of the migrating Bark lieo to wander far 



