E. T. CRESSOX, JR. 3 



with each other in an irregular .^pot at the post- vertical.-? ; a third 

 pair descend vertically from the main pair to the posterior orbits of 

 the eyes. 



The principal differences between this and its variety ajH^t^tta are 

 given below. 



:vlicro|»eza (^liircansi) aiiil>i$;na vnr. nov. (PI. I, fisrs. 1. 2). 



Male. — Yellow to whitish below, marked with black or brown as follows: a 

 median frontal vitta from the black ocellar tubercle nearly to the base of an- 

 teniife; vertex and upper part of occiput, also a brown spot on the occiput under 

 the neck ; a spot in each antennal fovese ; second and base of third antennal joint 

 and the bare arista; dorsum of thorax limited on each lateral margin by a yellow 

 stripe running from the neck to base of wing, this yellow stripe encroaches on 

 the dorsum anteriorly, constricting the black portion to about the width of the 

 neck ; postalar callus yellowish. The scutellum brownish, with a darker median 

 spot. The pleura with a brown stripe running from the neck to, and connecting 

 with, the black metanotum ; a brown or l)lack stripe on the ventral part of the 

 sternopleura running from flie fore to the middle coxte. Dorsum of abdomen 

 black, with narrow yellow or whitish posterior and lateral margins of segments 

 2-6, wider on the sixth. Genitalia yellow, with brownish marks; the yellow 

 clasps beneath the fourth segment conspicuously developed (see Figure 2). All 

 coxx whitish ; femora dark yellow, without rings; tibiae darker yellow, black at 

 apex; all tarsi black. PFijtf/s yellowish-hyaline ; veins rufous; apical cell open; 

 posterior cross-vein slightly bowed out; anal cell not acute. 



Female similar, but the frontal vitta is wider; antennse entirely black; the 

 yellow margins of the sixth abdominal segment not broader than the preceding 

 segments; first joint of the ovipositor nearly one-half as long as the abdomen, 

 brown, yellow on the lateral margins towards the apex ; second joint black. 



Length 6-7 mm. 



Numerous specimens of both .se.xes. Cloudcroft and Highrolls, 

 New Mexico (Viereck and Rehn). 



This is without doubt a variety of M. UircdiKi Town., being dis- 

 tinguished by the entirely black vertex, and the niesonotum without 

 the yellow median area. 



C^ALOBATA Meigen. 

 Illiger's Magazine, ii, 276, 1803. 

 Head not conical, but more or less hemispherical or rounded ; the 

 lower part only of the occiput generally being turgid ; antenna? 

 short, third joint lounded or oval. Thorax stout, but more or le.ss 

 attenuated anteriorly. Abdomen i-ather stout; the genitalia some- 

 times greatly developed. Auxiliary vein of wing present; discal 

 and second basal cells separated by the usual cross-vein ; last two 

 sections of the fourth vein of about equal length ; apical cell nar- 



TRANS. AM. ENT. SOC. XLXXIV. JANUARY. 1908. 



