139 
home. Its life history is not nnhke that of plant-lice already de- 
scribed. The adult is about the size of a pin-head, or a little larger, 
Fig. 30. Pea-louse, Macrosiphiiin pisi. winged viviparous female. 
Greatly magnified. 
pale green, and soft. It may be winged (Fig. 30) or wingless 
(Fig. 31). The winter is passed either in the tgg or the adult 
stage, and usually on clover, from which it migrates to the pea in 
spring, sometimes multiplying enormously on this crop. 
Fig 31. Pea-louse, Macrosiphiim pisi. wingless viviparous female. 
Greatly magnified. 
Natural Enemies. — Many parasitic and predaceous insects prey 
on the pea-louse and materially aid in checking its rapid multipli- 
cation, the parasites not infrequently becoming numerous enough 
to control it completely. (Fig. 32.) 
