68 Journal of Agricultural Research voi.x, no. a 



from vertex to cauda, 2.24 mm; legs short, the tibia; being about equal in length to 

 the antennae. 



Spring migrant. — Varies considerably in size, but the following measurements 

 represent about the average. Antennal segments: I, 0.064 mm.; II, 0.064 mm.; 

 111,0.448 mm.; IV, 0.144 mm.; V, o.imm.; VI, 0.08 mm. Segment III of antenna, 

 with 25 to 30 annular sensoria on the lower surface of the segment and almost encir- 

 cling it; segment IV vidth 7 or 8 and segment V with 5 or 6. Segment VI usually 

 without sensoria except the permanent ones. Forewing about 2.5 mm. long and 

 0.96 mm. broad. Hind tibia, 0.738 mm.; hind tarsus, 0.144 mm. Legs slender. 



In comparing the spring migrants of E. pyricola and E. lanuginosa 

 some differences are encountered. These are principally in the antennae 

 and are shown in the accompanying illustrations, reproduced from 

 photographs. It will be noted that the antennae of E. lanuginosa (Pi. 9, /I) 

 are considerably heavier than those of E. pyricola (Pi. 9, B, E). Seg- 

 ments IV and V seem also to be comparatively larger and armed with 

 more and heavier sensoria. Segment VI, as compared with V, is some- 

 what shorter in E. lanuginosa than in E. pyricola. There are available 

 for study, however, only a few specimens of E. lanuginosa. It seems 

 quite probable that these represent only variations in the species and 

 that, when a long series of E. lanuginosa is available, specimens will be 

 found similar to the American forms. 



Specimens of fall migrants upon European pear stock (Pi. 9, C) are 

 without doubt the same species as that occurring in America (Pi. 9, D). 

 It is possible that these specimens are in reality the fall migrants of 

 E. lanuginosa. This can be proved only by a study of reared European 

 material, which, under present conditions, it is impossible to obtain. 



DEVELOPMENT OF THE GALLS AND GALL APHIDS 



In a former article (2) it has been mentioned by the writers that the 

 fall sexuparous migrants leave the pear roots upon which they have 

 developed and fly to elm trees to deposit the sexes on the trunks and 

 limbs. These migrants settle on Ulmus americana and U. campestris. 

 The latter tree is distinctly preferred; in fact, no perfect galls have been 

 produced on the former. The sexed female after mating deposits a 

 single egg in a crack in the bark or underneath a bud scale. 



The eggs during the winter are reddish, greenish red, or greenish 

 brown, but immediately before hatching appear grayish brown, due to 

 the color of the embryo. The empty shell is dirty white. 



From this egg hatches the young stem mother which ascends a trunk 

 or limb and seeks an expanding leaf. In 191 6 hatching commenced 

 March 23 and extended until April 18, the majority hatching during the 

 first two weeks of April. 



The newly hatched stem mother is oval in shape, bare and shining, of 

 a yello\vish or brovmish olive hue with small black eyes and hyalin 

 appendages and beak. The thoracic region is lighter in color than the 



