AMERICAN DIPTERA. 297 



submarginal and posterior cells wide open ; the anal cell closed 

 at the margin or slightly petiolate. 



After establishing the generic name Lasiopogon, Loew dis- 

 covered that it was already used as such in botany, and so 

 changed his name to Daulopogon, which was adopted by 

 Osten Sacken in his Catalogue (1878). As there is no rule 

 demanding such a change, Dr. Williston was justified in re- 

 storing the older name in his Manual of N. Am. Diptera (1896). 

 Osten Sacken states that this genus is quite abundantly rep- 

 resented in California, but the difficulty in recognizing the 

 species from descriptions led him to describe but one species 

 in his Western Diptera. 



SYNOPSIS OF SPECIES.* 



1. Legs reddish-brown, abdomen polished black; the posterior mar- 



gins and hind corners of the segments brownish, the latter 



grayish pruinose terricola. 



Legs black, in arenicola yellowish-gray 2. 



2. Abdomen grayish pruinose, with a dark spot on the anterior 



lateral margins of segments 2-6 3. 



Abdomen with the grayish bloom confined chiefly to the posterior 

 margins of segments 2—6 4. 



3. Bristles of body pale arenicola. 



Bristles of body black opaculus. 



4. Dorsum of thorax with two narrow widely separated, distinct 



black stripes bivittatns. 



Dorsum of thorax with stripes, but not as above. 



tetragrammus. 

 This key has been made with the type material before me. 



Lasiopogon arenicola. 



Daulopogon arenicola Osten Sacken, West. Dipt., 310, 1877. 



" c? ? • — Length 7-8 mm. — Brownish-gray; abdominal segments 2-6 

 each with a pair of semi-circular brown spots at the base. 



"Brownish-gray, sometimes with a tinge of yellowish; the mystax 

 and the few hairs on the vertex and on the upper part of the occiput 

 yellowish- white; those on the lower part of the occiput pure white; 

 antennae black. Thorax with two, rather distant, brown stripes, ex- 

 panded and somewhat diverging anteriorly; the hairs and bristles on 

 the dorsum whitish; scutellum with a quantity of long, erect, whitish 



* This key does not include the recently published species quadri- 

 vittatus, which Mr. Jones says is quite closely related to arenicolor. 



TRANS. AM. ENT. SOC, XXXV. (38) AUGUST, 1909 



