INSECTS INJURIOUS TO SMALL GRAINS 



135 



in the spring is by far the best means of controlling this pest, 

 while burning the stubble previous to plowing, and a rotation 

 of the crop, will also be of considerable aid. 



The English Grain-louse * 



The most common plant-louse affecting wheat and other small 

 grains is a large green species which is always to be found on 

 wheat plants, but which occasionally increases very rapidly, and 

 clustering on the ripening 

 heads sucks the juices so 

 as seriously to injure the 

 quality and weight of the 

 wheat. 



In the North the first 

 individuals are found on 

 young wheat in April, 

 though during open win- 

 ters they may be found 

 on the plants, and in the 

 South they continue to 

 reproduce during most of 

 the winter in open sea- 

 sons. The aphids feed 

 upon the leaves until the 

 grain commences to 

 head, when they assem- 

 ble on the heads among the ripening kernels. The females give 

 birth to live young, bearing from 40 to 50 each, which become 

 full grown in ten days to two weeks, and then reproduce, as is the 

 usual method of reproduction with plant-lice (see page 390), so that 

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

 as to be hardly noticeable, in a few 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, 



* Macrosiphum granaria Buckton. Family Aphididce. A nearly related 

 species, Macrosiphum cerealis Kaltenbach, has very similar habits, is commonly 

 associated with the species, and has not been distinguished from it by most 

 writers. It may be recognized by lacking the blackish markings on the 

 abdominal segments. See Pergande, Bulletin 44, Bureau of Entomology, 

 U. S. Dept. Agr. 



FIG. 115. The German grain aphis(Afocro- 

 siphum cerealis Kalt): a, 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.) 



