558 [December 



dried specimen. On the whole, I know scarcely a single group of Insects, 

 not even excepting Aphidx, where the imago affords so few good and 

 reliable characters as in the Gecidomijia of the willow, which is the 

 more provoking as the number of species is so considerable. G/"/*. The 

 galls most of them afford very good, constant, and definite characters, 

 and as yet I have found no two galls undoubtedly distinct, that cannot 

 be sharply and effectually separated, with the exception of the Tenthred- 

 inidous galls, 8. ovum n. sp. and *S^. ovuluni n. sp., which occur on two 

 different willows. 



Osten Sacken has said that all the larvas of Cecidomyidse have 13-joint- 

 ed bodies, the supernumerary joint, which bears the breast-bone, being 

 placed between the head and the 1st thoracic (stigma-bearing) segment ; 

 and that the number and position of the stigmata are normal, one pair 

 on the 1st thoracic segment and eight pairs on the first eight abdominal 

 segments. {Dipt. N. A. pp. 181—2.) I agree with Schaum, that, con- 

 trary to the opinion of Westwood, no insect in any of its states has, in 

 reality, more than 12 joints to the body, i. e. 3 thoracic and 9 abdomi- 

 nal, and I can discern but 12 joints, exclusive of the head, in the larva 

 of any of the Gecidomi/ia of the Willow, the first joint bearing the 

 breast-bone on its inferior surface and dorsally rather short, the last 

 composed of little else but two tubercles transversely arranged and di- 

 rected backwards. And it appears to me, (though of this I would not 

 be so certain,) that in a very elongate and large larva ( C. s. siliqua n. 

 sp. ?) where the joints were unusually hunched and distinct, there was 

 a pair of spiracles to every joint but the one that bears the breast-bone 

 and the 12th or anal one, all arranged in a lateral row i of the way to 

 the hind end of each joint. In any case there was certainly a pair of 

 spiracles on what I consider as the 1st abdominal joint, but what, ac- 

 cording to Osten Sacken, is the metathorax. In two or three other 

 specimens belonging to the same species I was unable to see the spira- 

 cles so distinctly, but still I saw them. 



Lati'eille, Audouin, Schaum, and many other European entomolo- 

 gists, have asserted that no insect in any of its states has any metatho- 

 racic spiracle. Loew, however, agrees with Westwood in considering 

 the spiracle in front of the Dipterous halteres, which the above authors, 

 most incongruously as it seems to me, maintain to be abdominal, as truly 

 metathoracic. (^Dipt. JSf. A. Intr. p. xiv.) In the larvae of insects 



