ALDRICH AND DARLINGTON. 67 



THE DIPTEROUIS FAIVIIL.Y HEL.01II YZID^. 



BY J. M. ALDRICH AND P. S. DARLINGTON. 

 (Plates III-IV.) 



[Note. — This family of flies was taken up for study and revision by Mr. 

 Darlington while a senior student in the University of Idaho. At the time of 

 his gr.'idnation in June, 1907, he had nearly finished most of the genera, includ- 

 ing the drawing up of descriptions of the species, new and old. At this time his 

 appointment as horticultural inspector in an important field at Wenatchee, 

 Wash., necessitated his immediate departure. As we had assumed obligations on 

 all sides by borrowing material, there was no course open to me but to complete 

 the work, which after some delay I have done. My part, aside from a general 

 review, has Been to work up the genera Leria and Siligo, and to prepare the 

 illustrations. The new genus l^iligo and its two species, and the new species of 

 of L^ria (glanca), should be credited to me; the other new genus, Porsenus, and 

 the remaining new species, six in number, should be credited to Mr. Darlington, 

 whose industry and keen discrimination left little for me to do as far as his time 

 permitted him to go. — J. M. Aldrich.] 



This small family of Acalyptrate Muscidse is readily distiuguished 

 by the following characters : wings with auxiliary vein and second 

 basal cell distinct, and a row of spines along the costa ; vibrissse 

 present; fronto-orbital bristles only one or two ; all the tibiae with 

 preapical bristles. 



Czerny, from a slightly different view point, defines the same 

 group as follows : "The Helomyzidse belong to that series of groups 

 of Acalyptratse which possess convergent or crossed (also called 

 decussate) postvertical bristles. They are distinguished from all the 

 other groups of this series by the simultaneous occurrence of vibrissse 

 and an entirely separate auxiliary vein." The postvertical bristles 

 are located on the back of the head, somewhat behind the ocelli, 

 and are easily seen. 



For practical purposes the costal spines are almost sufficient to 

 distinguish the family, but these do occur in a few species outside 

 the family, especially in Oyrtojiotum, Ccenia and Facellia, of our 

 fauna. Cyrtonotiim (PI. IV, figs. 8, 9) has a short first longitudinal 

 vein, united towards the tip with the auxiliary ; Ccenia has the 

 typical Ephydrid face, and the second basal cell united with the 

 discal ; while Fucellia has a row of fronto-orbital bristles extending 

 to the base of the antennae, some six in number. 



TRANS. AM. ENT. SOC. XXXIV. MARCH. 1908. 



