ART. 9 T\\'0-WINGED i^ i^IES OF TBIBE MILTOGRAMMINI ALLEN 9 



Pachyophthalmus is represented by a limited number of species 

 occurring in Europe and the American continents. The adults ap- 

 parently do not frequent barren sand and denuded ground. They 

 are attracted to flowers, bask on shrubby foliage in the sunlight, and 

 have been noted about habitations, as would be expected from the 

 peculiar host relationships. The members of the genus, so far as 

 known, are biologically superimposed on wasps which build mud 

 nests under shelter or in hollow stems, including members of the 

 families Sphecidae and Eumenidae. The manner in which the female 

 establishes her progeny and the subsequent larval development have 

 not been observed. Rau found the puparia of one species lodged in 

 a hollow stem containing the nests of Odynerus. When associated 

 with the common ''dirt daubers" Pelopaeus and Trypoxylon, which 

 build their nests indoors, it is not known whether the maggots 

 pupate within the mud cells of their hosts or leave them to seek 

 other shelter for the transitional stage. The members of the genus 

 Pachyophthalmus are more distinctly aerial in habit than the other 

 North American genera of Miltogrammini. So far as is known, all 

 of the activities of adult, larval, and pupal stages take place in a 

 stratum extending from a foot or more to several feet above the 

 ground. This is a noteworthy biological specialization in a group 

 of flies, most of which pass the immature stages under ground, and 

 never rise, as adults, but a few inches above the ground. 



KEY TO NOKTH AMERICAN SPECIES OF PACHYOPHTHALMUS 



1. Thoracic vittae not continuous over scutellum; hind tibia on outside with a 



complete row of bristles extending to the apex; the fourth abdominal and 

 genital segments wholly black 3. 



Thoracic vittae continuous over scutellum; hind tibia on outside with a row 

 of bristles not extending far beyond the middle 2. 



2. Fourth abdominal segment and genital segments wholly black; parafrontals 



outside the two frontal rows conspicuously setulose hinei, new species. 



Fourth abdominal segment and genital segments yellow; parafrontals outside 

 the two frontal rows, at most with scattered microscopic bristly hairs 



floridensis Townsend. 



3. Anterior clasper of the male genitalia much shorter than the penis, and with 



bluntly pointed tips signatus (Meigen). 



Anterior clasper of the male genitalia nearly as long as the penis, and with 

 exceedingly sharp, delicate, incurved hooks at the tip. 



distortus, new species. 



UNRECOGNIZED SPECIES OF PACHYOPHTHALMUS 



erythrura Van der Wulp, Biol. Cent.-Amer., Dipt., vol. 2, p. 89, 1890. 



Described from a single male from Presidio, Mexico, and assigned to Milto- 



gramma. Type in British Museum. 

 sarcophagina Van der Wulp, Biol. Cent.-Amer., Dipt., vol. 2, p. 90, 1890. 



Described from a female from Atoyac, Vera Cruz, Mexico, and assigned 



to MiUogramma. The type and one other specimen in British Museum. 

 04292— 26t 2 



