E. T. CRESSON, JR. 109 



THE NORTH AMERICA]^ »$I'ECIES OF THE DIPTEROUS 

 FA!»IIL,Y SCEXOPIIVID.E. 



BY E. T. CRESSON, JR. 



SCENOPINID^. 



(Plate II.) 



In working over some material from Mexico and the southwest- 

 ern United States, I found some species of this family that appeared 

 new to me, and it being a small family I thougiit it a good oppor- 

 tunity to make a short revision of the family, as known to North 

 America, comprising notes and a few descriptions of undescribed 

 sexes. 



This paper is intended to be of use, especially to the student who 

 has not the collection or library at his disposal needed for the deter- 

 mination of the species of this family. The tables will aid in sepa- 

 rating the genera and species. 



The figures given here were drawn, mostly, from these southwest- 

 ern species, aud will help in the generic descriptions; and the data 

 given, except where otherwise mentioned, is from the material in 

 the collection of the Acad. Nat. Sci. Phila. 



TABLE OF GENERA. 



1. Eobust, short species ; abdomen flat, wide O- 



Slender, elongate species; abdomen cylindrical Pi^eiidatrichia. 



2. First posterior cell open in margin Sceuopiiius Latr. 



First posterior cell closed and petiolate ; body clothed with scale-like hairs. 



IVIelalrichia Coq. 

 SC'EIVOPINUS Latr. 



The species of this genus are robust, and generally black. Head 

 more or less hemispherical, higher than long; front descending; 

 scutellum distinctly separated from the thorax by a wide suture, its 

 apex not depressed; abdomen flat, broad; each segment with a 

 transverse furrow and their posterior margins turned up ; the second 

 segment has two minute approximated opaque spots on its dorsum. 

 Legs short and stout. Wings rather broad but longer than the 

 thorax ; first posterior cell open in the margin. 



TKANS. AM. ENT. SOC. XXXIII. APEIL, 1907 



