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STATE BOARD OE AGRICULTURE. 



THE GRAIN APHIS. 



(Siphonophora avenae Fab.) 



In 1889, a general outbreak of the grain-louse occurred in Michigan. In 1900 this 

 was repeated, though on a smaller scale. Specimens of wheat infested with the lice 

 were received from various places, and an examination of the college wheat fields 

 showed a fair sprinkling of the pests. Fortunately the lice did not make their appear- 

 ance until after the wheat was well headed nor did the attack last long. Fig. 11 gives an 

 idea of the appearance of this louse. It is green in color with black markings. Both 

 winged and wingless forms are present, the latter predominating. From the hinder 

 part of the abdomen, there projects a pair of slender tubes, the cornicles, whose office 

 it is in most other lice to secrete honey-due. The insect is known to work on many differ- 

 ent hosts, such as wheat, rye, barley, oats, soft chess, orchard-grass, Holcus and Poa, 

 Sorghum, canary-grass and others. 



Fig. ll. — Grain Aphis. Siphonophora avenue. Winged female greatly enlarged. Original. 



On the 27th of June, 1900, the farm of Mr. W. F. Potter, of Williamston, was visited. 

 At that time, the aphids were disappearing, but just previously they were very numer- 

 ous on wheat, chess, and beardless barley. The greener and younger plants were most 

 badly infested, the stronger ones escaping a part of the trouble. A large number of 

 heads of grain were collected and placed in suitable cages in the laboratory. Next day 

 a number of parasites were to be seen moving about the cage, contrasting strongly in 

 their quick nervous movements with the slow stolid motions of the lice. Each succeed- 

 ing day brought out a fresh crop of parasites for about a week and they continued to 

 emerge from time to time even longer. These parasites (Fig. 12) are black and dirty 

 yellow in color and smaller than the lice. They have four wings, and move very quickly, 

 constantly running about as if in search of something, and in truth they are, for if one 

 be closely watched and ifs movements followed the interesting process of egg laying is 

 likely to be observed. Wandering around among the plant-lice, one of the females will 

 approach a young louse, make a careful examination, no doubt to make sure that no 

 other parasite has been before her, and then standing firmly and squarely before or at the 

 side of the stolid and immovable louse, the parasite will bring her abdomen forward 

 between her three pairs of legs and with the ovipositor at the end. pierce the side of 

 the louse, quickly depositing an egg inside the body of the victim. The stop is a short 



