INSECTS INJURIOUS TO BEANS AND PEAS 



293 



The Pea-aphis * 



Large green plant-lice often become so abundant on the foliage 

 and pods of garden-peas as to kill the plants. Prior to 1899 the 

 pea-aphis had not been a serious pest in this country, but during 

 that and the following season it caused a loss of several million 

 dollars to pea-growers on the Atlantic coast from North Carolina to 

 Nova Scotia and as far west as Wisconsin, especially where peas 

 were extensively grown 

 for canning. During 

 1901 injury was by no 

 means as serious, and has 

 materially decreased 

 since then, though spo- 

 radic injury occurs 

 almost every year in some 

 section. General injury 

 occurs only periodically 

 for reasons mentioned be- 

 low. The pest seems to 

 occur throughout the 

 States east of the 100th 

 meridian and possibly 

 farther west. It is an old 

 enemy of peas in Eng- 

 land, where it destroyed 

 the crop as long ago as 

 1810, and it has long been 

 known in Europe as an 

 enemy of peas, clovers, 

 vetches and related 

 plants. 



FIG. 250. The pea-aphis (Macrosiphum pisi 

 Kalt.): winged and wingless viviparous fe- 

 males and young enlarged. 



Both wingless and winged aphids occur together throughout 

 the season, the latter predominating whenever food becomes scarce. 

 The winged forms are from one-eighth to one-seventh of an inch 

 long, with wings expanding two-fifths of an inch. The body is a 



* Macrosiphum pisi Kalt. Family Aphididce. See Chittenden, Circular 

 43, Bureau of Ent., U. S. Dept. Agr.; Sanderson, Bulletin 49, Del. Agr. Exp. 

 Sta.; Folsom, Bulletin 134, 111. Agr. Exp. Sta. 



