228 MAINE AGRICULTURAL EXPERIMENT STATION. I9IO. 



coxae; the antennae 5-jointed, with the joints subequal. Bark-feeding. 

 Orange in color. Undergoing one moult and then being at once dis- 

 tinguished 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 antennae, the joints subequal in length; by the 

 shorter legs, with smaller claws to the tarsi, and more distinct terminal 

 capitate hairs or pulvilli. The skin is transparent, the body filled more 

 or less with fatty globules. The female is nearly pyriform, and aver- 

 ages 0.4 mm. in length. A single egg is visible through the translucent 

 skin, and, according to age, occupies m.ore or less of the whole of the 

 bod5^ The male is narrower and smaller, the penis being bulbous, with a 

 couple of spine-like genital clasps. 



"This species is very closely allied to the European S. uhni (Li'in.), 

 and until I was able to compare it with actual specimens I was in doubt 

 whether to look upon it as a mere variety or a distinct species. Judg- 

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

 by a figure sent me by Mr. Buckton, it differs from ours, ist, in bend- 

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

 under side of the leaf; 2nd, in having a number of small rounded or 

 verrucose swellings. These differences in their dwellings are strongly 

 presumptive of structural differences in the insects themselves ; an^l the 

 fact that S. amcricana does not attack the European Elms, either in 

 Shaw's Botanical Gardens at Saint Louis, or in the grounds of the De- 

 partment of Agriculture, points in the same direction. Differences are 

 indeed easily enough made out if we take the more or less imperfect 

 descriptions and figures of ulmi* but are less apparent when the actual 

 specimens are compared. The following are the more important differ- 

 ences, least subject to variation, between the winged female of ulmi as 

 compared with those of americana : ttlmi is a longer-winged species 

 averaging y.;^ mm. in expanse; the abdomen, wing-veins, and stigma 

 are darker; the terminal distance between ist and 2nd discoidals slightly 

 greater; the 3d joint of antennae is relatively longer; the annulatioris 

 are less deep and more numerous (those on 3d joint averaging 30) ; 

 joints 5 and 6 are smoother, i. e., without annulations, but they are 

 more setous ; joint 5 is shorter than 4; the apical, narrowed part of 6th 

 joint is relatively longer and more pointed; the subcostal vein of hind 

 wings is less straight; the cubital vein is often continuous to very near 

 the subcostal, while I have not found any tendency of the kind in 

 americana, the tendency being in the opposite direction, or to become 

 shorter ;the 2d discoidal of hind wings shows a tendency to fork ; the 

 booklets on costa of hind wings are 3 in number while in americana 

 there are normally four;t the legs are more setous." 



*"Koch's figure (evidently copied by Kessler) is faulty in several re- 

 spects, and fails to indicate the hook-angle of hind wings, or the corre- 

 sponding thickening of front wings a fault that is, however, common to 

 most of Koch's figures. 



f'These booklets get so easily broken off that they are not to be relied 

 on ; yet the normal number on most of the Pempliiginae I have examined 



