298 DIPTERA OF NORTH AMERICA. [PART IV. 



its inner end is farther from the root of the wings than the inner 

 end of the submarginal cell ; the small cross-vein, although 

 present in C. glahrata, is wanting in the majority of the specimens 

 of C. nodicornis ; and lastly, there are four, instead of five 

 posterior cells. 



However much C. glahrata and nodicornis may differ from 

 Triogma in their general appearance and in their coloring, they 

 have more affinity to this genus than to the typical Cylindrotomse. 

 This affinity appears ; in the structure of the antennae, the 

 sculpture of the thorax, the shape of the discal cell, the number 

 of posterior cells, the structure of the lamella of the male forceps. 

 The American C. nodicornis 0. S. differs from C. glahrata in 

 having, in normal specimens, the submarginal cell in close con- 

 tact, at the basis, with the discal cell (Tab. I, fig. 7, wing of C. 

 nodicornis), in consequence of which the small cross-vein is 

 wanting. The same is the case with both species of Triogma. 

 In the Proc. Entom. Soc. Philad. 1865, p. 239, I did not hesitate 

 to locate C. nodicornis in the genus Triogma; but at that time 

 I had not seen the European C. glahrata. It will be necessary 

 ultimately to establish a new genus for these two species (it may 

 be called Liogma, from the character of the furrows which are 

 more smooth than those of T'riogma). But I abstain from 

 characterizing this genus, as I am not quite certain about the 

 position of G. nigrivenlris Loew, and diversa Walk., which I 

 have not seen. 



The word Cylindrotoma is derived from xvxtvSpoj, cylinder, and 

 ti/xvLo, I cut, in allusion to the shape of the antennal joints of the 

 typical species. 



The larva of Cylindrotoma distinctissima lives on the under 

 side of the leaves of different plants, as Viola, Anemone, Stel- 

 laria, and eats elongated holes in them ; it is green, elongated, 

 flattened, linear, but little attenuated at both ends, with a longi- 

 tudinal crest along its back, consisting of a row of fleshy pro- 

 cesses, pointing backwards; the lateral margin is broad, with 

 many excisions, formed by fleshy points. The larva, before trans- 

 forming, leaves the plant upon which it fed, and fastens itself to 

 some grass-stalk, upon which it undergoes the pupa state. The 

 pupa is not unlike that of some Lepidoptera; the thorax bears 

 several horny processes. The first description and the only figure 

 of this larva have been given by Schellenberg (Genres d& 



