498 PROCEEDINGS OF THE NATIONAL MUSEUM VOL. 113 
are Mr. Curtis W. Sabrosky of the U.S. Department of Agriculture 
at the U.S. National Museum, Dr. J. R. Vockeroth of the Canadian 
Department of Agriculture, Dr. C. H. Curran of the American Museum 
of Natural History, Dr. William L. Brown, Jr., of Harvard University, 
and Mr. C. B. D. Garrett, who permitted me to examine the many 
important types in his private collection. 
I am indebted to Dr. Maurice T. James for the many helpful sug- 
gestions given me during the course of this study, and to Mr. George 
C. Steyskal, who gave assistance in the interpretation of the male 
terminalia. 
Taxonomic Treatment 
The division of the Heleomyzidae into the subfamilies Suilliinae 
and Heleomyzinae is supported by biological as well as morphological 
characters. As noted by Bezzi (1911), the larvae of the Suilliinae 
develop in fungi, whereas those of the Heleomyzinae are found ina 
variety of other habitats, including nests of birds and the burrows of 
small mammals. They are separated by the following key: 
Frontal plates oblique, directed inward anteriorly and distinctly separated from 
the eye margins; propleural bristle absent; sixth vein not reaching wing 
margin; 1 fronto-orbital bristle on each side . . . . . SUILLIINAE (p. 498) 
Frontal plates parallel to eye margin, not oblique, propleural bristle present; 
sixth vein reaching wing margin; 1 or 2 fronto-orbital bristles on each side. 
HELEOMYZINAE (p. 510) 
Subfamily Suilliinae 
Key to the Genera of Suilliinae 
1. Humeral bristle present... .. . SAB, yeh htc eae . . . Allophyla (p. 508) 
Humeral bristle absent . ... . Ss Vai bins ted Rls Gee Siete > ae es en 2 
2. One pair of dorsocentral bristles. . . ..... . . . .Porsenus (p. 498) 
Five pairs of dorsocentral bristles . . ....... . . . Suillia (p. 499) 
Genus Porsenus Darlington 
Porsenus Darlington, in Aldrich and Darlington, 1908, p. 69.—Czerny, 1924, p. 64. 
This genus is known only from the single type female of Porsenus 
johnsoni Darlington. 
Porsenus johnsoni Darlington 
Porsenus johnsoni Darlington, in Aldrich and Darlington, 1908, p. 70.—Czerny, 
1924, p. 64. 
I have seen the type of this species (USNM Type 29348). It 
agrees with the original description of the genus and species, except as 
follows: supra-alar bristles 1+1; scutellum with a pair of strong 
apical bristles, a much weaker lateral bristle on one side only (no 
