Timely Hints for Farmers. 263 



subtropical fruit-trees of Florida. In Salt River valley, in accord 

 ance with this general law, plant-lice are not particularly trouble- 

 some in the hot weather, but in the late winter and early spring 

 they flourish exceedingly, the same cool and mild weather which 

 permits the growth of garden vegetables being exactly suited to 

 their taste. In the Mesilla valley of New Mexico the winter and 

 early spring are too cold for the vegetables or lice, and the sum- 

 mer is hot, so here plant-lice are not much in evidence. It re- 

 sults from these facts that we have a region to the north and again 

 one to the south, troubled by plant-lice and capable of growing cer- 

 tain crops, while an intermediate region has few lice and is less suit- 

 able for the crops in question. 



From a popular standpoint, plant-lice may be divided into 

 three groups : 



1. Naked lice. 



2. Woolly lice. 



3. Lice living in galls. 



The last mentioned are commonly seen on cottonwood trees, 

 their globular or oval galls being very conspicuous on the twigs or 

 leaves. If one of these galls is broken open, the lice are found 

 within. These gall-lice do no serious injury, but if the galls are 

 considered unsightly they may be cut off and burned in the early 

 summer. 



One of the gall-producing kinds is the famous Phylloxera of 

 the vine. This creature has done enormous damage in Europe, 

 but in America, where it is native, it is not regarded with any fear. 

 Dr. J. B. Smith says: "I have seen vineyards in New York and 

 New Jersey in which almost every leaf showed these galls, yet 

 withal no real injury had been done. In other words, most of the 

 native American vines are able to sustain the attack of the spe- 

 cies." 



The woolly lice are known by their secretion of a white wool- 

 like substance, really consisting of minute waxy threads, so that 

 they look like little patches of mildew. The commonest of 

 such lice is the woolly louse of the apple, or Schizoneura lanigera 

 (See figures 4 and 5). This creature is probably a native of Europe, 

 although in England it is known as "American Blight." It is 

 certainly not a native of Arizona, but has been brought there on 



