Aphids or Plant-lice 



Lime-sulphur Mixture 



In the case of those aphids which cause the leaves to curl, spraying in 

 winter or early spring to kill the eggs and newly hatched lice is most 

 effective. For this purpose the lime-sulphur mixture has proved satis- 

 factory. This mixture may be made on the farm, but it can be pur- 

 chased in a concentrated form from insecticide dealers at a cost not 

 exceeding that of making it. The trees or shrubs to be treated should 

 be thoroughly sprayed before the buds begin to open. 



Tobacco Decoction 



This is made by boiling tobacco stems or powder in water. Two 

 pounds of the former to four gallons of the latter make a mixture suffi- 

 ciently strong for general use. Do not let the mixture boil violently as 

 this drives off some of the nicotine, thus reducing its strength. 



DESCRIPTION AND LIFE HISTORY 



In size and color the plant-lice vary greatly. Among the larger 

 species the bright red Macrosiphum so common on the stems of golden- 

 glow in late summer is very conspicuous. Contrasted with this is the 

 small green species commonly found on the under side of rose leaves and 

 clustered about the unopened buds. 



Many aphids have two tubes near the tip of the abdomen (Fig. 23, 

 Page 113). These are called honey tubes, and it was originally supposed 

 that the sweetish liquid or honey dew which is discharged from the ali- 

 mentary canal was discharged through them. 



The mode of reproduction of plant-lice differs from that of other 

 insects. The louse hatching from the over-winter egg and all of the 

 individuals of several subsequent generations produce living young with- 

 out the aid of the male element. This "asexual" reproduction, as it is 

 called, usually continues until cold weather approaches. In the fall 

 true males and females are produced. These mate and the females 

 produce the eggs which carry the species over winter. 



In some species the young of a single individual consist of both males 

 and females, while in the case of others one set of females bear all female 

 and another all male young. 



The rate of reproduction is exceedingly rapid, a generation being 

 produced every few days during warm weather. This rapid multiplica- 

 tion results in widespread damage, many times, before the presence of 

 the lice becomes known. 



NATURAL ENEMIES 



Were it not for the natural enemies of plant-lice in the form of pre- 

 dacious and parasitic insects, fields, orchards and gardens would soon be 

 overrun by them. 



Chief among these natural enemies are the lady-beetles, two of which 

 are shown in Figure 10, Plate II, Page 13, and Figure 15, Plate IX, Page 

 27, and their larvae in Figure 15, Plate II, Page 13, and Figure 23, Plate 

 IX, Page 27. 



115 



