148 INSECT PESTS OF FARM, GARDEN AND ORCHARD 



multiply with great rapidity, and where so few were present as 

 to be hardly noticeable, in a fe\v weeks they will be swarming 

 over the heads in myriads. As the small grains ripen they migrate 

 to various grasses and are not much in evidence during midsummer, 

 but later migrate to volunteer oats and wheat, upon which they 

 subsist until fall wheat is available. Owing to the cool \veather 

 of fall and the fact that but few individuals survive the attacks 

 of their parasites during the summer, they rarely become abundant 

 enough to do any damage to grains in the fall. So far as know r n, 



the\" hibernate over 

 winter among the leaves 

 of the growing plants, 

 enough surviving both 

 snow and cold to infest 

 the crop the next spring. 

 Whether true males and 

 females produce eggs on 

 the grain is unknown, for 

 though they have been 

 reared under artificial 

 conditions, they have 

 never been observed in 

 the field. Professor F. L. 

 Washburn observed at 

 least fourteen generations 

 up to Xovember 8, 1907, 

 in southern Minnesota. 

 As with other aphides, both winged and wingless individuals 

 occur throughout the season. The wingless individuals are 

 about one-tenth inch long, with black antennae as long 01; longer 

 than the body, are of a yellowish-green color, often slightly 

 pruinose, and long black nectaries extend from either side of the 

 abdomen. The winged individuals are about the 'same length, 

 with a wing expanse of about three-eighths inch, with antennae 

 a third longer than the body, and are of the same general colora- 

 tion except that lobes of the thorax are brown or blackish, and 



FIG. 107. The German grain aphis (Macro- 

 siphum cerealis Kalt) : o, winged migrant ; 

 b, nymph of same; c, wingless partheno- 

 genetic female; d, same showing exit hole 

 of parasite enlarged. (After Riley, U. 

 S. Dept. Agr.) 



