46 INSECTS AFFECTING THE ORANGE 



the infested twigs and brandies die ; often the entire top is lost. The 

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

 the injury by throwing out shoots from bdow. 



When the tree reaches tbis 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 off the srales," 

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

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

 when the branches become crowded, wander off and on to new growth; 

 their course is, therefore, naturally 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-larva3, 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 deluskm 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 may even permanently recover without the 

 aid of applied remedies, but very young orange trees do not possess 

 the powers of resistance of adult trees ; their tops 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 of the budded portion. 



Influence of Climate. The retarding action of cold weather upon the 

 development of Scale-insects, and the acceleration produced by the 

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

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

 annual generations. The species of Diaspin found in the Northern 

 States have all, or nearly all of them, a single generation, occupying the 

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

 United 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. 



