June, 1912.1 Aldrich : Two Western- Species of Ephydra. 101 



structure, more or less yellow at base ; hind femora incrassated, with long 

 hairs below near base, their tibije noticeably curved, long-hairy on the inner 

 side toward the end, shining black on the apical half of the hind and inner 

 side ; hind tarsi short, with the usual brush of yellow hairs below on three 

 joints and a few long hairs above, directed mesially : fourth joint a little 

 longer than the third, with a process toward the apex on the inner side, 

 which bears a conspicuous tuft of black hair; fifth joint normal. 



Wing brownish, veins brownish-yellow at base, costa a little spiny, hind 

 crossvein somewhat oblique and bicurved. 



Length 6.2 mm. ; of wing 5.6 mm. 



Female. — Greatly resembling the male in all points but the hind femora 

 scarcely thickened, the hind tibise nearly straight, the hind tarsi a little longer 

 than in the c?, plain, with only three or four bristles above. Length 6.5 mm. ; 

 of wing 5.6 mm. 



Five males and one female, collected on the salt marshes of San 

 Francisco Bay, Cal., adjacent to Palo Alto, April 20 and 26, 1906. 

 I searched in vain for additional material in August, 191 1. Xothing 

 is known about the life history. 



This species was originally described from Brownsville, Texas. 

 The generic reference might be argued either way, as the claws are 

 not very straight, and very minute pulvilli are present. Mine's 

 description is meager, and I did not suspect the identity of my mate- 

 rial until I learned from E. T. Cresson, Jr., to whom I sent part of it, 

 that he had compared it with the types of viridis and found them 

 identical. I have therefore given a fuller description of the species. 



Table of Species. 

 The described species of Ephydra from the region of the Rocky 

 Mountains and westward may be tabulated as follows: 



1. With 6 dorsocentrals ; a large gray opaque species, front hairy and with 



several bristles inclined mesially on the lower part hians Say. 



With s dorsocentrals ; front with i pair of small bristles below, inside the 

 orbitals. or with none 2 



2. Frontal orbits shining; 3d joint of antenna with a long erect hair on 



outer side atrovirens Loew. 



Frontal orbits pollinose ; 3d joint of antenna without such a hair 3 



3. Tarsi bright yellow, contrasting with the black-green femora and tibiae. 



atiripes .'Mdrich. 

 Tarsi not contrasting with tibise 4 



4. Very large bronze-green species with yellow knees ; (^ with a conspicuous 



tuft of hairs on inner side of 4th joint of the hind tarsus, .viridis Hine. 

 Not as described ; (^ not ornamented 5 



