8 BULLETIN UNITED STATES GEOLOGICAL SUEVEY. [YolY. 



at tlieir extreme base, and not confluent witli it. [The wing- venation is very constant. 

 Out of nearly 100 specimens examined, I have found only an unusual shortening of 

 the cubital in two individuals. ] The larva and pupa in this third generation differ 

 from the winged insect in being more reddish and in haviug the antennaj ringed with 

 less distinct constrictions, in the legs being paler, in the claws being stronger, and in 

 the basal joint of tarsus being more connate with the terminal joint. They have a 

 distinct annulated elevation at each side posteriorly — a sort of pseudo-honeytube. 

 When tirst born, they are of a pale duU yellow, and the antennal joints are more nearly 

 subequal in length. 



Fourth genei-ation.— That from the first winged females : Differs from the preceding 

 in the promuscis being, much longer, in the antennsB having but five joiuts, the third 

 being somewhat longest and the first the shortest, but all often being of much more- 

 nearly equal length, with no annulated constrictions. The color is more decidedly 

 orange. When ncAvly hatched, the thickened end of the promuscis often extends one- 

 half the length of the body beyond anus. The legs are also long and stout, and the 

 basal joint of the tarsus is distinct, but not separated. The capitate hairs are obsolete. 

 It is born Avith an enveloping ijellicle or pseudovum, and though of a bright red with 

 pale legs at first, soon becomes brownish, Avith dark members. 



Fiftli generation. — The counterjDart of the second. 



Sixth generation. — Second winged : Eesembles the tliird, but usually rather lighter- 

 colored, with the wing- veins, the spinous armature of surfaces, and the constrictions of 

 antennse less strong, and with the third joint of antennse rather less in length than 

 the terminal three together. 



Seventh generation. — True sexual individuals : Born within an egg-like pellicle. With 

 stout promuscis reaching to between middle and hind coxse ; the antennse G-jointed, 

 with the joints subequal. Bark-feeding. Orange in color. Undergoing one moult, 

 and then being at once distinguished from the other forms by the brighter orange- 

 yellow color, the rudimentary mouth, the more simple eyes (composed of three facets), 

 by the shorter, 5-jointed antennsB, the joints subequal in length ; by the shorter legs, 

 with smaller claws to the tarsi, and more distinct terminal cajiitate hairs, or pulvilli. 

 The skin is transparent, the body filled more or less with fatty globules. The female 

 is nearly pyriform, and averages 0.4™'» in length. A single egg is visible through 

 the translucent skin, and, according to age, occupies more or less of the whole of the 

 body. The male is narrower and smaller, the j)enis being bulbous, with a couple of 

 spine-hke genital clasps. 



Tliis species is veiy closely allied to tlie European B. ulmi (Linn,), and 

 until I was able to compare it witL. actual specimens, I was in doubt 

 whether to look ujDon it as a mere variety or a distinct species. Judging 

 from Kessler's figure and description of the European leaf-curl, and by 

 a figure sent me by Mr. Buckton, it differs from ours, 1st, in Ijending 

 upward, i. e., the stem-mother settles on the upper instead of the under 

 side of the leaf 5 2d, in having a number of small, rounded or verrucosa 

 sweUings. These differences in their dwellings are strongly presmnptive 

 of structural differences in the insects themselves ; and the fact that S. 

 americana does not attack the European Elms, either in Shaw's Botani- 

 cal Gardens at Saint Louis, or in the grounds of the Department of Ag- 

 riculture, points in the same du^ection. Differences are indeed easily 

 enough made out if we take the more or less imperfect descriptions and 

 figures of ulviii* but are less ai^parent when the actual specimens are 



* Koch's figure (evidently copied by Kessler) is faulty in several respects, and fails 

 to indicate the hook-angle of hind wings, or the corresponding thickening of front 

 wings, a faiilt that is, however, common to most of Koch's figures. 



