ISOPENTHES. 97 



sides of the thorax and of the abdomen, yellowish, more or less mixed with black 

 hair ; more distinct tufts of black hair appear on the sides of the abdomen at the end 

 of the first segment, and especially on the sides of the distal half, where the black 

 hair decidedly prevails over the yellow, and forms a conspicuous fringe. The surface 

 of the thorax and abdomen shows (under the magnify ing-glass) a scattered, appressed 

 scale-like tomentum of a coppery-red colour, not dense enough to cover up the ground- 

 colour ; the long, soft, erect hair upon the abdomen is blackish, but shows in a certain 

 light whitish reflections. Venter greyish, with hair of the same colour, or more 

 yellowish. Head black, with short, erect, black pile ; a thin covering of scale-like 

 golden hairs on the face and on the occiput ; on the front the scales are more coppery- 

 red and less numerous. Proboscis withdrawn within the oral opening. Antennae with 

 the third joint short bulbiform, with a style three or four times the length of the joint, 

 ending in a minute bristle. Legs brownish-yellow, covered with yellowish scales, and 

 beset with black bristles ; tarsi darker. The brown colour on the wings, whether seen 

 in a light transmitted through it or reflected from its surface, appears uneven, and 

 shows, in the former case, numerous transverse streaks of a slightly paler shade, rather 

 evenly scattered between the veins, over the whole surface ; when a strong light is 

 reflected from the surface these paler spots show a golden sericeous reflection ; the paler 

 spots on the anterior and posterior cross-veins, and near the origin of the second vein, 

 are very little apparent. 



In my specimens the encroachment of the brown upon the third submarginal (next 

 to the first posterior) cell is almost imperceptible, or none at all ; in the six specimens 

 from Oaxaca, in Prof. Bellardi's collection, this encroachment is greater and more in 

 conformity with Jaennicke's figure. 



2. Isopenthes jaennickeana, sp. n., 6 ? . (Tab. II. fig. 4.) 



Body black ; a stripe of whitish pile on each side of the thorax ; wings dark brown, except the margin between the 



apex and the tip of the axillary cell, the distal half of the first posterior cell remains hyaline. 

 Length 8-11 millim. 



Eab. Mexico, Northern Sonora (Morrison). 



Exceedingly like I. blanchardiana, but easily distinguished by the indicated difference 

 in the coloration of the wings and by the distinct stripe of whitish pile on each side of 

 the thorax. The scale-like, scattered, appressed, coppery-red tomentum on the thorax 

 and abdomen mentioned in the description of /. blanchardiana is very inconspicuous 

 here, though some traces of it are perceptible on the thorax. The boundary of the 

 dark colour of the wings shows the following differences : — it does not encroach upon the 

 third submarginal cell ; the hyaline spot in the expanded portion of the marginal cell is 

 slightly larger; likewise the hyaline space at the end of the first (or inner) submarginal 

 cell ; the distal half of the first posterior cell is hyaline ; within the fourth posterior 

 cell the black does not reach the margin of the wing.— Twenty-five specimens ( d ? ). 



biol. centk.-amee., Dipt., November 1886. o 



