ART. 4. REVISION OF THE FAMILY THEREVIDAE—COLE. 3 
Loew published on the Therevidae of Europe and made some inter- 
esting observations on the genus Thereva. 
Osten Sacken’s Catalogue of the North American Diptera, published 
in 1878, listed 4 genera and 43 species in the family, counting Walker’s 
6 species, which were listed in a footnote, with the observation that 
most of them would coincide with Say’s or Loew’s species, the others 
being unrecognizable from the descriptions. Four of the specific 
names used in this catalogue have been relegated to synonymy and 
two are described from Cuba and are not included in the list later 
given by Aldrich. 
In 1893 Coquillett wrote a synopsis of the genera Thereva and 
Psilocephala and in 1894 a short revision of the family. He described 
a large number of species but made no extensive study of the family. 
In 1912 Kréber published his Revision of the Therevidae of North 
America, and, having a good general knowledge of the group, his 
paper was a valuable contribution to the knowledge of the family. 
The work is incomplete, due in part to the lack of material for study, 
and many species are included in the tables from reading the descrip- 
tions. Some of the new species are based on one or two specimens, 
often only one sex being described, and as no figures are given there 
may be some difficulty in separating the species from closely allied 
forms, even though the descriptions are usually quite complete. 
Kroéber had a tendency to “lump” species that were superficially 
alike, judging from the material in the collection of the United States 
National Museum that was sent to him for determination. Under 
Psilocephala haemorrhoidalis there were found no less than seven 
distinct species, all allied to haemorrhoidalis, but clearly different 
when carefully examined. Kroéber’s work on the Therevidae of the 
world, published as one of the parts of the Genera Insectorum in 
1913, is of great assistance to students of the group; in this monograph 
he recognizes 442 species, grouped in 38 genera.” 
Aldrich (1905), in his Catalogue of North American Diptera, gives 
6 genera and 71 species in the Therevidae. In his revision of the 
North American species Kréber lists 9 genera and 81 species. The 
writer has erected 4 new genera and has described 38 new species in 
the following pages, making a total of 13 genera and 118 species, 
and there is little doubt that many more species will be added during 
the next few years. 
STRUCTURAL CHARACTERS. 
In general appearance the Therevidae are somewhat like the more 
weakly bristled robber flies which are placed in the subfamily Dasy- 
2 After completing this manuscript the writer obtained a copy of Kréber’s paper (Beiheft zum 
Jahrbuch der Hamburgischen Wissenschaftlichen Anstalten) published in 1914. Critical remarks and 
diagnoses of species have been added in the galley proof. One new genus and fifteen new species are 
described from North America. 
60466—23—Proc.N.M.vol.62——14 
