25 



The Grain Aphis. (Siphonophora Granaria*) 



(PLATE IV.) 



There has rarely, if ever, been a more general and severe 

 attack of this aphis than in the last season. Complaints 

 came from all quarters, and wheat ears were sent in swarming 

 with aphides in all stages. In going through the country 

 in August their presence could be plainly seen by the colour of the 

 wheat. Rust and mildew were very prevalent also, but in some 

 fields there was a peculiar appearance, principally due to aphides. 

 It was found, upon examination of the ears of wheat infested with 

 aphides, that many of the grains were shrivelled, and not fully 

 developed ; also, that in a great number of the ears there were 

 no grains in the chaff near their bases. Some growers assessed 

 the injury at from 5 to 15 per cent., others, at from 15 to 20 per 

 cent. . It was, however, most difficult to make correct estimates 

 of the loss from this cause ; but it is obvious that the continuous 

 suckings of quantities of aphides round the forming grain, and 

 until just before it ripened, must have materially affected its 

 quantity, weight, and quality. 



From inquiries made as to cultivation and previous cropping, 

 it appeared that no circumstances of this kind affected the 

 attack. Wheat plants on all kinds of soil and in every des- 

 cription of situation alike suffered. Nor does it seem that the 

 weather influences had much to do with the number and 

 persistency of the aphides. The season was not very wet and 

 not very dry. In former attacks it had been considered that 

 dry weather and east wind caused, or at least, intensified 

 them. Professor Riley, of the United States Department of 

 Agriculture writing of a kindred insect, " The Grain Louse, 

 Aphis avence," says : " That it may always be expected in a 

 tolerably wet year that was preceded by a dry one." It might be 

 " said that 1892 was a tolerably wet year," but 1891 was certainly 

 not dry. 



It was observed that plants near the outsides of wheat fields 

 were attacked worse than those some distance in, and that small 

 enclosed fields were worse than large extents of wheat land. 

 Some reports showed that foul land was worse than land free 

 from weeds, also that wheat after clover ley was the most 

 injured. 



DESCRIPTION AND LIFE HISTORY. 



The wingless female (Plate IV. a and &),. which brings forth 

 living aphides is greenish or brownish green. The colour varies 

 very much between green and brown, so that it would sometimes 



* Mr. Hovdler Buckton, F.R.S., has courteously allowed Plates IV. and V. to 

 be copied from his valuable work A Monoyraph of British Aphides. 



