46 INSECTS AFFECTING THE ORANGE 



the infested twigs and branches diej often the entire top is lost. The 

 roots and trnnk, however, survive, and the tree endeavors to repair 

 the injury by tlirowing out shoots from below. 



When the tree reaches this impoverished condition matters usually 

 begin to mend. The Bark-lice upon the dead or dying branches perish 

 by starvation, the parasites reassert their sway, and slowly the tree re- 

 gains its health and vigor, but seldom its pristine beauty. 



The opinion is often expressed that the tree will •' throw oft' the scales," 

 or that they will "disappear in time at the ends of the branches." The 

 facts upon which this belief is founded are simply that tlie young lice, 

 when the branches become crowded, wander off an<l on to new growth ; 

 their course is, therefore, naturallj' upward and outward. When the 

 advancing army reaches the ultimate branches, the insects crowd upon 

 the smaller twigs and leaves, killing them rapidly and involving them- 

 selves in the common destruction. The tide of scales is then checked, 

 while the enemies thrive and multiply, feeding upon the dead and starv- 

 ing Coccids. There then occurs one of those sudden oscillations of the 

 balance which are familiar enough to entomologists ; the unseen ene- 

 mies increase and the scales visibly diminish. The tree meantime has 

 rest and may under favorable circumstances recover its vigor, in which 

 case the trouble for the time being is over, and the lost branches are 

 quickly replaced. 



More frequently, however, the new growth, which always pushes out 

 rapidly in such cases, will, as soon as it hardens, be overrun by the 

 crawling scale-larvse, newly hatched from eggs which were not involved 

 in the destruction of the mother insects, and after an interval a new 

 brood will be found again in possession. This process may be repeated 

 many times in the tops of full-grown trees, and the orange-grower at 

 each ebb in the tide will perhaps flatter himself with the delusion that 

 the scales have in some mysterious manner disappeared at the ends of 

 the destroyed branches. Well-grown trees may submit again and again 

 to these vicissitudes. They maj- even permanently recover without the 

 aid of ai)plied remedies, but very young ca^mge trees do not possess 

 the powers of resistance of adult trees; their to})s being small and 

 their branches short, they are usually entirely overrun in a single sea- 

 son, and, if not attended to, sustain irreparable-injury, resulting, in the 

 case of budded trees, in the destruction ot^the budded portion. 



Infiuence of Climate. — The retarding a -tion of cold weather upon thi' 

 development of Scale insects, and the acceleration i)rodu('ed by tlie 

 higher temperature of the summer months, has already been mentioned. 

 The inlluence of a warm climate is shown in the increased number of 

 annual generati(»ns. The si)ecies of Diasi)ina' found in the Korthern 

 States have all, or nearly all of them, a single generation, occui)ying the 

 summer months. The same species have in the warmer portions of the 

 (Jnited States at least two broods, and in the extreme South those 

 species with which orange-growers have to contend produce not less 

 than three and some of them more than four generations. 



