1916.] NATURAL SCIENCES OF PHILADELPHIA. 541 
in their arrangement, being on the same face on the even segments; 
the ninth and eleventh segments are smaller and lie between the 
long, verticillatc tenth and twelfth segments; thirteenth segment of 
the flagellum long, sigmoid, bearing three long hairs at the apex. 
Wings with the median cross-vein present, connecting M1+2 with 
Type of the subgenus, Rhaphidolahis flaveola Osten Sacken. 
The curious pallid fly that I have deemed best to separate from 
the other species of the genus is anomalous in many respects and 
may eventually be placed nearer to Tricyphona, where indeed it was 
provisionally assigned by Needham.^^ It is certainly more distinct 
from Rhaphidolabis than is Plectromyia which has herein been con- 
sidered to have subgeneric value. Under these circumstances it 
may be better to call the genus Plectromyia, that name having 
page-priority over Rhaphidolabis, but for the present the latter name 
has been retained. 
The American species of the genus may be separated by the 
following key: 
1. Antennae 15-segmented; cross-vein m present (subgenus Rhaphi- 
dolabina). (Northeastern United States.) 
flaveola Osten Sacken. 
Antennae 13-segmented; cross-vein m absent 2 
2. Cell Ml absent (subgenus Plectromyia). (Northeastern United 
States.) modesta Osten Sacken. 
Cell Ml present (subgenus Rhaphidolahis) 3 
3. Cell R2 petiolate 4 
Cell R2 sessile 6 
4. Wings whitish hyaline with a dark brown, oval stigma. (Eastern 
Rocky Mountain region.) neomexicana Alexander. 
Wings without a clearly defined, dark brown stigma 5 
5. Antennae of the male elongated; Rs long, straight, the distance 
between Sc^ and the origin of the sector being less than the 
length of the sector. (Western United States.) 
polymeroides Alexander. 
Antennae of the male short; Rs short, arcuated, the distance 
between Sc2 and the origin of the sector about two times the 
length of the sector. (Eastern United States.) 
tenuipes Osten Sacken. 
6. Coloration grayish brown, the praescutum with three dark bro^^^l 
stripes ; abdomen dark brown mth paler caudal margins to the 
segments; wings very pale brown, the radial sector very short, 
arcuated or angulated. (Northeastern United States.) 
cayuga sp. n. 
18 Twenty-third Report of the New York State Entomologist, PI. 25, fig. 3, 
1907. as Amalopis. 
