2 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 123 



lar setae uniseriate. Mesoscutum strongly arched with posterior 

 slope distinctly flattened, with grayish or brownish pollen toward 

 sides; acrostichals absent; 5 pairs of large dorsocentrals; 2 scutellars, 

 a small hair on the lateral scutellar margin; pleural surface with 

 grayish pollen. Femora with preapicals usually weak, sometimes 

 not distinct. Longitudinal veins of wing straight to slightly curved, 

 all, including veins 3 and 4, diverging for most of length; crossvein 

 nearly as long as or longer than last part of vein 5; vein 6 totally 

 absent. Calypter pale with dark margin and some dark setae. 

 Abdomen short, tapering; hypopygium sessile, usually large and 

 projecting somewhat forward under the abdomen. 



Type-species: H. intricata Robinson, original designation. 



The species occur on soil or rocks at edges of streams and lakes or 

 on moist rock surfaces near seepage and waterfalls. They sometimes 

 alight but more frequently hover close to the surface of the substrate. 

 The species may be very particular regarding positions where the}' 

 alight and the males of some species seem to favor slightly different 

 habitats from the females. 



Most collections of Harmstonia have come from limestone regions. 

 The genus is apparently absent from regions of North Carolina where 

 limestone is conspicuously lacking. Recently I have collected H. 

 intricata along a stream flowing over aged serpentine but pH was 

 not checked. One species is found on the West Indian island of 

 Dominica, which is primarily volcanic in origin, but the Dominican 

 streams that have been tested show a rather high pH. 



Key to the Species of Harmstonia 



1. Foretibia with a distinct row of anterodorsals, hind tibia usually with a 



distinct row of posterodorsals; hypopygial lamella broadly oval or elliptical 



and rounded apically 2 



Fore- and hind tibiae without rows of prominent dorsals; hypopygial lamellae 

 (except H. intricata) bearing obvious slender apical projections .... 7 



2. Hind tibia with short stout black apical and subapical setae; hypopygial 



lamella covered with hairs; face of female bearing two distinct setae . . 3 

 Hind tibia without distinct black apicals and subapicals; surface of hypo- 

 pygial lamella glabrous; face of female with three to six distinct setae . . 4 



3. Femora blackish; middle tibia with two anterodorsals; abdomen of male 



straight (Mexico) H. recta, new species 



Legs including femora yellow; middle tibia with one anterodorsal; abdomen 

 of male curved (Mexico) H. pubescens, new species 



4. Legs totally brown; body and wings both over 1.5 mm long; hypopygium 



large, over 0.5 mm long (Mexico) H. megalopyga, new species 



Legs partly yellow; body and wings less than 1.25 mm long; hypopygium 

 distinctly less than 0.5 mm long 5 



5. Knob of halter pale (Mexico) H. ornata, new species 



Knob of halter black or brown 6 



