NATURAL SCIENCES OP PHILADELPHIA. 249 



spots along the tergum ; they are dark brown in the middle and ferruginous on 

 the margins. Wiags with a brown stripe along the costa ; another one along 

 the pobrachial vein; a brown band unites both across the central cross-veins; 

 the rest of the wing is hyaline. 



Length from 13 to 15 lines. 



I possess specimens from Trenton Falls, (nob.), Massachusetts (Mr. Scudder), 

 and Connecticut, (Mr. Norton.) 



Dicranota Zett. 



Antennae 13-jointed.(*) Eyes hairy. Wings with two area?. Tibiae with 

 small, but distinct spurs at the tip. Pulvilli distinct. Mediastinal cross-vein 

 far remote from the tip of mediastinal vein, anterior to the origin of the 

 petiole, and situated about the middle of the anterior margin. Structure of 

 the (^ genitals analogous to that of Amalopis and Pedicia. Head 

 small ; proboscis and palpi very short ; a distinct gibbosity on the head be- 

 hind the antennae ; feet of moderate size and thickness. 



The wing of my D. rivularis is exactly like Mr. West wood's figure of 

 that of D. pavida in Walker's Ins. ,Brit. Dipt. iii. tab. xxx. f. 7, having 

 no discal areolet, two cross-veins between the upper branch of the radial vein 

 and the subcostal, and one fork behind the subapical areolet. The' neuration 

 varies in different species of the genus, but the position of the mediastinal cross- 

 vein seems to be an essential character. 



This genus was first established by Prof. Zetterstedt on his D. G-uerinii; 

 afterwards, Mr. Haliday, in Walker's Ins. Brit. Dipt. iii. p. 306, added to it 

 D. pavida Hal., D. bimaculata Schum., and D. senilis Hal. How- 

 ever, D. bi maculata Schum. is mentioned in Prof. Zetterstedt's work (Dipt. 

 Scand. torn. x. p. 3897, No. 72,) among the Limnobiae. How should have 

 Zetterstedt misplaced a species belonging to a genus established by himself, 

 unless he overlooked its having 13, and not 16, joints of the antennae ? 



D. senilis Hal., as figured in Ins. Brit. Dipt. iii. tab. xxvii. f. 3, is quite 

 distinct from the other speoies by the presence of a discal areolet, by its hav- 

 ing one cross-vein, instead of two, between the subcosta and the upper branch 

 of the radial fork ; and above all, by the position of the mediastinal cross- 

 vein,- which is posterior to the origin of the petiole, and not far distant from 

 the tip of the mediastinal vein. If the latter character is correctly figured on 

 the plate, I would doubt whether this species belongs to Dicranota. 



The affinities of this genus with A malopis and Pedicia (hairy eyes, 

 position of the mediastinal cross-vein structure of the $ genitals, etc.,) are 

 manifest; it is distinguished by the short palpi, the number'of the joints of 

 the antennae, etc. 



The only species described below, agrees in its characters with D. Gu eri- 

 n i i Zett. on which, as mentioned above, the genus was first established. 

 Only Prof. Zetterstedt does not make any mention of the hairy eyes, which he 

 may have overlooked. (See also the remark about the antennae, at the end 

 of the description.) 



D. rivularis. Cinerea, thorace vittis tribus fuscis, femorum basi pallida, 

 alis subcihereis ; long. lin. 3-4. 



Head cinereous, front and vertex slightly infuscated ; proboscis, palpi and 

 antennae black ; the latter in both tf and > short, not reaching the base of 

 the wings, joints of the fiagellum subglobular, (see the observation at the end 

 of the description). Thorax cinereous with three distinct, blackish stripes, 

 the intermediate one broad, and, in some specimens, distinctly capillary ; 

 lateral one abbreviated before, extended over the scutum behind ; scutellum 

 and metathorax cinereous, posterior half of the latter blackish ; halteres 



(*) As to the length of the antennae, see observation at the end. 



1859.] 



