232 MAINE AGRICULTURAL EXPERIMENT STATION. I91O. 



British insects which I have examined show also four hooklets 

 on the lower wings." Buckton. British Aphides. Vol. Ill, 

 p. 100, foot note to a reference to Riley's statement in regard 

 to ulmi). 



12. 'With ulmi the legs are more setous.' 



It would seem that the relative differences noted by Riley 

 may be locational or seasonal, — at least not specific. At any 

 rate the 1909 Maine americana correspond more closely to 

 Riley's 1879 characterization of ulmi (of Europe) than they 

 do to his description and figures of americana. 



As to the differences in the leaf-curl or pseudo-gall of ulmi 

 and americana a mistake has been recorded. Riley"^ says: 

 "Judging from Kessler's figure and description of the Euro- 

 pean leaf-curl, and by a figure sent me by Mr. Buckton, it differs 

 from ours, first, in bending upward, i. e., the stem-mother set- 

 ties on the upper instead of the under side of the leaf ; second, 

 in having a number of small, rounded, or verrucose swellings." 



Kessler's figure is misleading because it is inverted, that is, 

 the ventral surface of the leaf is placed uppermost on the plate. 

 But his description of the gall in the same publication (1878) 

 to which Riley evidently had not access, states explicitly enough 

 that the insects are on the under side of the leaf.f 



Buckton's figure of iihni leaf-curl, Vol. Ill, Plate CVIII, is 

 misleading for the same reason, — it is inverted on the plate, 

 which places the ventral side of the leaf uppermost. That 

 Riley was mistaken nevertheless in thinking that the ulmi leaf- 

 curl differed from that of am,ericana in this respect is abundantly- 

 shown by the following citations. 



Koch, 1857, p. 264, says of ttlmi, "die eine seite des Blattes 

 sich unterwarts zusammenrollt." 



*Riley and Moiiell on Aphididae, page 8. 



j"Schisoneura ulmi afficirt den grossten Theil der einen Halfte des 

 jungen Blattes und zwar an der Unterseite der Zeit, wann dasselbe aus 

 der Knospe hervorwachst. Dadurch entsteht auch hier intercalates 

 Wachsthum in der Art, dass die Zellenbildung an und langs der 

 Hauptrippe, aber in die Regel niclit bis an die Spitze und an den Grund 

 des Blattes, am energischsten vor sich geht, wodurch der schon 

 ausgebildete Rand sich nach der Unterseite des Blattes umbiegt und 

 diese Blatthalfte mit der Zeit eine gelblich griine, wulstige Rolle bildet 

 (Fig. 5)." 



