of certain species of Willow. — Part 2nd. 255 



preceding year; and two 9 , bred many years ago, in the same season 

 that the gall was produced, bo far as I recollect, from an undescribed 

 Cecidomyidous bud-gall— Vitis fusus Walsb, MS. — composed of bundl- 

 es of 6 — 50 fusiform galls growing on the stem of the wild grape-vine, 

 Vitis cordifolia, each gall attached by a single point, and about \ an 

 inch long. 



Genus NEMATUS.— Gall-makers. 



No. 20. Gall S. pomum, n. Bp. — On S. cordata, (and very rarely on S. discolor.) 

 A smooth, fleshy, sessile, globular or slightly oval, monothalamous gall, re- 

 sembling a miniature apple, .30 — .55 inch in diameter, growing on one side of 

 the midrib of a leaf, and extending to its edge or sometimes a little beyond it. 

 The principal part of the gall generally projects from the under side of the leaf, 

 and only about 1-fith of its volume from the upper side, although very rarely it 

 is almost equally bisected by the plane of the leaf. Scarcely ever more than one 

 gall on a leaf, and very rarely two of them more or less confluent, so as to seem 

 like one kidney-shaped gall. External color greenish-yellow, generally with a 

 rosy cheek like an apple, especially on the upper surface, and often with many 

 dark little dots on its surface. Internal color whitish. The above is the appear- 

 ance presented July 31 when the gall is fully matured, but as early as May 24 

 it has nearly attained its full size, and has the rosy cheek very conspicuous. 

 Abundant but rather local. Described from v »ry numerous specimens. As to 

 the occasional occurrence of this gall on S. discolor see under No. 21 bis. An 

 analogous gall is formed in Europe on the leaves of various kinds of willows by 

 Nematus gallicola Westw. 



Larva. May 24 the larva is only about .10 inch long. On June 11 it is white, 

 .10 — .13 inch long. On July 24 it is .15 inch long. On July 30 — 31 it is .15 — .20 

 inch long, of a pale greenish-white color, the head pale brown, with the usual 

 eve-spots blackish and distinct. Legs freely moveable; 12 abdominal prolegs on 

 joints 5 — 10 and 2 anal prolegs on joint 12. On Sept. !». I noticed in a jar containing 

 several hundred of these galls, three larvae crawling about which were .35 — .40 

 inch long, of a pale cinereous color, with some pale dusky markings and the usu- 

 al dusky eve -pots. Their legs were freely moveable. Most probably, judging 

 from their size, these last appertained to the inquilinous N. mendicus, n. sp., one 

 specimen of which I bred the following spring from the same lot of galls. Of 

 the very large number of the gall-making N. s. pomum bred therefrom the same 

 spring, almost all spun up inside their galls, and only a few between and among 

 them, there being no earth in this jar under which they could have retired if 

 they had been so minded. 



Pupa unknown. 



Imago. Nematus s. pomum. n. sp. — 9 Shining honey yellow. Head with 

 the eye-, a quadrate spot sometimes barely enclosing the ocelli, sometimes al- 

 most reaching the antennas, but even then always separated from the eyes bj 

 a tolerably wide orbit, and also the tips of the mandibles, all black. Clypeus 

 emarginate in a circular arc of aboul 90°. Labrum rounded at tip. Occiput al- 

 ways with a capillary black line located in the usual la.teral stria, ami slowly con- 

 verging from each posterior ocellus to the disk, where it meets a transverse capil- 

 lary black line, so as to enclose a trapezoidal space, which is rarely occupied by a 

 black cloud. Antennae £ as long as the body, joints 3 — 5 subequal, 6 — S slowly 

 ahorter and shorter, 9 generally a- long as 8, the scape black, the flagelluro 



