THE PEA APHIS WITH RELATION TO FORAGE CROPS, 7 



there were many bare spots where the aphid had killed the clover locally, and in the 

 growing clover were many centers of new infestation, due doubtless to migrant winged 

 females. All of the clover in that part of the country was more or less injured; not 

 only old clover but also the first-year growth. Returning to the same region the fol- 

 lowing summer to see the consequences of the injury, I did not stay long, for it was 

 hard to find a field of clover anywhere. The farmers reported that the clover had 

 been "winter killed," to their surprise, since the winter had not been a severe one 

 and the clover had often survived worse winters. 



Mr. Harold Morrison (1912), discussing the abundance of this insect 

 in Indiana, says: 



Two years ago [1910] it was so common in-many clover fields near the city [Indian- 

 apolis] that the clover remained on the ground for more than a week after cutting 

 without showing signs of curing. The clover stems were so plastered with honeydew. 

 that the moisture could not evaporate from them. 



We have seen clover fields in Indiana so badly infested that the 

 plants would be covered with the so-called "honeydew," a sticky, 

 sweetish fluid ejected by the aphis from the anus. Walking through 

 such an infested field, one"s trousers would appear green, so thickly 

 would they be covered by the plant-lice, and ruined by the honeydew 

 which covered the plants. While it is seldom that fields are killed 

 outright as described by Dr. Folsom, there can be no doubt that the 

 heavy infestations, which are so common, have a decided weakening 

 effect on the plant and much of the winter killing of clover can be 

 traced back to the depredations of the pea aphis. Most probably 

 much damage to clover has been overlooked or attributed to other 

 causes, for while a crop may be injured on large field crops such as 

 clover the injury will be overlooked unless the field is almost killed 

 outright, and subsequent effects, such as the weakening of the vitality 

 of the plants, is too often attributed to "winter killing," as Dr. Folsom 

 has pointed out. Especially may this species be a very dangerous 

 clover pest if the weather conditions are favorable to aphides and a 

 long dry spell retards the growth of the clover. 



CHARACTER OF ATTACK. 



This aphidid prefers the young tender leaves and stems of its host, 

 but eventually it covers the entire plant. Garden and sweet peas, 

 being succulent plants, are seriously attacked and readily succumb 

 to the depredations of the aphides. Clover, particularly red clover, 

 on the other hand, is able to withstand considerable injury, but, as 

 has been noted, even this plant is not free from serious damage; in 

 fact entire fields of clover are sometimes destroyed. 



EFFECTS ON CATTLE OF FEEDING THEM INFESTED CLOVER. 



We have no definite reports of injury to cattle by feeding clover 

 hay which has been heavily infested with aphidids; indeed, we have 

 been informed by cattle feeders that such clover, which has a slightly 



