REPORT OF THE SOCIETY 1^ 



THE MOST COMMON PLANT LICE OR APHIDS. 



By W. Lochhead, Macdonald College. 



Plant-lice or aphids are gregarious sucking insects, often abundant on many 

 varieties of plants, and doing much injury. Three forms occur: 1. sedentary 

 wingless, viviparous, agamic females; 2. migratory, winged, viviparous, agamic 

 females; 3. sexual males and females — the females oviparous and wingless and the 

 males winged or wingless. 



In general, plant-lice are soft-bodied and green, sometimes brown or black. 

 The winged forms have four delicate wings with a few simple veins — the front 

 pair much larger than the hind pair. The sucking beak is three-jointed; the legs 

 and antennae are long and the eyes prominent. In autumn the sexual females 

 deposit eggs that hatch in the spring into females which are often termed "stem- 

 mothers." These produce living females which in turn produce living females, 

 and so on for several generations. As each female produces several young, and 

 these mature in a short time, reproduction is very rapid. When autumn ap- 

 proaches and food supply becomes scarce a brood of winged males and wingless 

 females is produced. The females produce the winter eggs. Sometimes agamic 

 female^ hibernate. 



Reproduction among the aphids may be represented diagramatically as 

 follows : 



Where O represents the overwintering egg, P the viviparous agamic wingless 

 form, and = P = the viviparous agamic winged form, and cf and 9 the sexual 

 forms. 



There are many species of plant-lice, some feeding on one variety of plant, 

 but many are capable of feeding on two or more varieties. Some feed for a time on 

 one host plant, then migrate to another for the summer, finally returning to the 

 first one in autumn. Some produce abnormal growths called galls, such as the 



