11 



remaining joints of the antennas, the tarsi and tip of nectaries are blackish, the apex 

 of the femora brownish or purplish, and the tibia? dusky toward the end. The 

 antennae are six jointed, the third joint and the spur longest and subequal in length, 

 each of them almost subequal to joints four and five combined. The nectaries are 

 similar to those of the stem-mother, with traces of the future clavate character of 

 the imago. 



Migratory female (fig. 1, a and e); second generation. — The winged form of this gen- 

 eration is extremely active and may be observed at favorable times to swarm in 

 considerable numbers, and, settling on the proper kind of trees, proceed at once to 

 deposit their young ones. The head and thorax of these migrants are of a polished 

 black, with the depressions or sutures of the thorax more or less distinctly greenish; 

 the eyes are brown; the antennas, terminal two-thirds of the femora, apex of the 

 tibia?, the tarsi, and nectaries are black. The abdomen is greenish yellow, marked 

 with three or four black, lateral spots in front and one or two beyond the nectaries; 

 the tail varies from dusky to black. The basal section of the femora and the tibia? 

 vary between green and yellowish green, whereas the median line and lateral margin 

 of the abdomen are frequently dark green. The expanse of their wings is about 7 mm 

 and the length of the body 1.5 to 2 mm . The antenna? are rather 'short and stout and 

 reach to or somewhat beyond the middle of the body; in the length of the various 

 joints there is more or less variation in different specimens and frequently in the 

 same specimen; the third joint and the spur are longest and generally subequal in 

 length, with the fourth next and the fifth shorter than either of them. Joint 3 is 

 always strongly tuberculated, frequently also the fourth and sometimes also, more 

 or less so, the fifth. The nectaries are of medium size or generally about as long as 

 the fourth antennal joint; as a. rule more or less, though sometimes distinctly clavate, 

 with the bulge toward the end am 1 most conspicuous on the inner side; the apex is 

 flaring. The tail'is curved upward, rather less than half the length of the nectaries, 

 elongate conical and rounded at the apex; its surface bears numerous minute points, 

 while on each side of its terminal half are about three curved bristles ; the last abdom- 

 inal segment is similar to that of the stem-mother. The venation resembles that of 

 Aphis; the stigma is elongate lanceolate and its vein arcuate, while the terminal 

 fork of the third discoidal vein is smaller than usual, sometimes minute or even 

 wanting in one wing or the other. 



The third generation is composed of both the apterous and the winged forms 

 which reaches maturity about the middle of May, while the fourth generation, which 

 has spread to various related trees or shrubs, makes its appearance about the middle 

 of June; the last or fifth generation, which' is usually small and scattered, may be 

 observed from the middle of June till the early part of July, after which time all 

 have disappeared, leaving the trees free of them until the middle of September, 

 when the pupiferous females or return migrants again make their appearance and 

 continue to do so until the middle of November, to restock the trees with sexual 

 females, which it takes about a month to bring to maturity, by which time, or from 

 about the middle of October, the winged males make their appearance, having in 

 the intervening time attained maturity on grain or grasses, and continue to do so till 

 the middle of November or, during favorable seasons, even later. 



The pupiferous females, or return migrants, are as a rule somewhat larger than the 

 spring migrants; their expanse of wings ranges between 6 to 8 mm and the length of 

 their body between 1.5 to 2.4 mm ; the antenna? are also somewhat longer, Avith the 

 third joint usually much shorter than the spur, though joints three to five vary just 

 as much in length and tuberculation, as well as in the size of the terminal fork, from 

 the spring migrants. The general coloration of the body has also become quite vari- 

 able. In some specimens the color is of a rather yellowish green with the lateral 

 spots very distinct, whereas in others it is of a grayish-green or dusky shade, or 

 sometimes almost black. All except the palest forms show a more or less distinct 



