1864.] 601 



ing, that certain European Willow-galls were the work of Aphis ? (See 

 above, p. 551.) On July 31st I found a bored and empty specimen of 

 the Tenthredinidous gall C. pomum tenanted in the same manner by 

 over a dozen Aphis. 



Larva. The larva in November is of a bright, shining, orange color, 

 immaculate, with the segments much hunched, .07 — .10 inch long and 

 from 3 to 4 times as long as wide. The breast-bone is clove-shaped and 

 exactly like that of G. batatas, but on comparing 10 specimens of that 

 species there can be no doubt of their specific distinctness. For the 

 larva of C. s. nodulus diifers from that of C. s. batatas, 1st in being 

 much more elongate, 2nd in being immaculate with sanguineous. 3rd 

 in being unusually shining and the segments more hunched than in any 

 Willow-gall Gicidomyia known to me except C s. siliqua. — Described 

 from 3 specimens. 



Pupa and imago unknown. 



No. 12. Gall s. batatas n. sp. — On S. humilis, (S. cordata? and S. discolor?) 

 A jjolythalamous gall of very variable shape and size, pale green when young, 

 the color of the bark when mature, growing on twigs .06 — .19 inch in diameter, 

 almost always some distance from the tip of the twig. Sometimes it resembles a 

 small kidney-potato pierced lengthways by a twig, and has then most generally 

 a smooth, polished surface studded with a few buds, one or two of which occa- 

 sionally give birth to a shoot, and it then reaches 1.35 inch in length and .60 

 inch in diameter. Sometimes it resembles a young apple pierced lengthways by 

 a twig, and it then attains a diameter of .50 inch. Sometimes it forms a hemis- 

 pherical or hemielliptic swelling, like a bunnion, on the side of the twig and 

 attains a diameter of .30 inch. Sometimes all these different shapes are strung 

 together one after the other in more or less close proximity, on the same twig. 

 Sometimes it is reduced to a small, elongate-oval enlargement of the twig for i 

 or J an inch ; and occasionally it becomes so irregular and so full of side-shoots, 

 bulges, cracks, roughnesses and lobes, as to defy description. Very rarely it is 

 terminal and assumes the form of 8. siliqua, but may be distinguished by the 

 , terminal bud not being elongated and tubiliform, and by being solid and not 

 nollow inside. On one occasion I found what had evidently been a S. siliqua 

 gall, occupied laterally by spongy matter containing 4 larvae undistinguishable 

 from those of C. >s. batatas, the elongated cell of the larva of C s. siliqua being 

 still in existence but contracted in diameter and empty. When these galls as- 

 sume the elongate bunnion-like form, they are undistinguishable externally 

 from the Tenthredinidous gall 8. ovum, which occurs on S. cordata. and 8. ovu- 

 lum, which occurs on the same willow as 8. batatas, but may be distinguished 

 on cutting into them by the fibres being linear and radiating from the twig, 

 whereas the other two galls are composed of a series of spongy lamellae at right 

 angles to the axis of the twig, and moreover, when laid open to their base, ex- 



