RAVAGES OF THE ARMORED SCALES. 45 



sufficient to sustain the wei^bt of the little aeronaut, or until in its sweep 

 it becomes entangled in tlie branches of a distant tree or shrub, and 

 forms a brid*;e upon which the si)i(ler readily crosses. 



The warm ascendinj>- currents of spring, the southeast trade-winds 

 in Florida, excite multitudes of spiders to set out ui)un their travels, 

 speeding them on their way and directing their course. At this season 

 of the year, when the migrations of insects are at their height, and all 

 nature is in restless activity, Scale-iusccts also ure most abundantly i)ro- 

 diu'tive, and the leaves and branches of infested trees swarm with their 

 young. Thus it is that in spring esi)ecially the Vi)iders, aided by the 

 winds, carry the Bark-lice in nuuibers and to great <H.stance-. 



GondUions furor able to their Increase. — There is good reason to believe 

 that Bark-lice, like many other destructive insects, <l<) not, as a rule, 

 originate the disorders which follow their attacks. An enfeebled con- 

 dition of the plant, from whatsoever cause it arises, is generally neces- 

 sary to provoke an invasion. Thoroughly healthy trees, even when in- 

 fected, may remain uninjured for years. The Scale iusects upon them 

 thrive ouly upon the lower or inside branches, and are held in check by 

 their natural enemies and i)arasites. An unfavorable atmospheric con- 

 dition, such as long-continued drought, the imj)Overishment of the soil, 

 neglect of cultivation, and the many obscure or utterly unknown causes 

 which produce " tliebaclc," yellow and streaked foliage, or other indi- 

 cations of vegetable indigestion, if such it, may be called, all tend to 

 foster Scale-insects and favor their ra[)id increase. 



In explanation of these facts, it may be conjectured, although it is 

 not, perhaps, susceptible of proof, that peculiar conditions of the sap 

 are especially favorable to the development of Scale-iusects, and att'ect 

 the reproductive functions, stimulating the females to greater produc- 

 tiveness. Observations show that the number of eggs (U'[)osited varies 

 considerably, and that the maximum number is i)roduced, not by soli- 

 tary iemales upon vigorous i)'auts, but by individuals of the advancing 

 1 rood taken from portions of the plant plainly affected by their attacks. 



Usual course of ,the Pent. — If it be true that outbursts of Scale-insects 

 commonly owe their origin to some disturbance in the coiulitiou of the 

 l)lant, it is no less a liict that their lavages not only aggiavate the 

 original trouble, but entail others, it may be, far more serio.is in their 

 consequences. The countless throng of Dark-lice not only weaken the 

 ])lant by sapping and diverting its \ ital juices and depriving it of uour- 

 isliii;ent, but tliey also strangle the parts which they infest by coaling 

 the surface and clogging its pores with their myriad bodies. Their 

 long, hair-like sucking beaks i)enetrate and thread the cellular tissues 

 of the growing bark, breaking through and altering its structure so 

 that the tender baric of the twigs and younger shoots is destroyed, 

 while the thicker bark of the tiunk and larger limbs hardens and be- 

 comes, as it is po|)ulai-ly termed, ''hide-bound." 



In this condition healthy growth is impossible. If neglected and al 

 lowed to be overrun by the pest, the growth of the tree is checked; 



