90 



UNITED STATES NATIONAL MUSEUM BULLETIN 2 2 4, 



small, short, the second considerably longer, spindle- 

 like and with an apical pore. Its pile is reduced to a 

 few dorsolateral and ventral bristly hairs. The an- 

 tenna is attached at the upper fourth of the head. The 

 first two segments are subequal in length and at least 

 twice as long as wide. The first segment bears near the 

 apex below a pair of long and exceptionally stout 

 bristles. Both segments with stiff, bristly hairs; third 

 segment wanting. 



Head, anterior aspect: The head of only moderate 

 width, the face below antenna is a little more than one- 

 fourth the width of the head, with parallel sides, uni- 

 formly pubescent with a number of scattered bristly 

 hairs over the whole length. On the epistomal margin 

 are 3 pairs of straight, stout, long bristles, and above 

 them an additional medial pair. Subepistomal area 

 extensive, oblique and nearly plane ; its lateral margins 

 are gently rounded and merging into the cheek. The 

 front is very slightly widened above the antenna; the 

 vertex is slightly convergent but almost as wide as the 

 face. The front is short and pollinose, the ocellar pro- 

 tuberance rather high with vertical sides and bearing 

 3 pairs of divergent bristly hairs ; sides of front with 

 3 long and 3 or 4 shorter, bristly hairs. Anterior eye 

 facets at most very slightly enlarged. 



Thorax : The height of thorax is moderate, uniformly 

 convex anteriorly and posteriorly and highest in the 

 middle. The mesonotum is densely appressed, micro- 

 setate, with pile undifferentiated. The thorax bears 

 the following complement of bristles : 4 pairs of very 

 weak, slender pronotal bristles and on the mesonotum 

 stout, long bristles; 1 posthumeral, 1 notopleural, 1 

 supraalar, 1 postalar, a scutellar pair, and no postdorso- 

 central bristles. On the metapleuron are 6 long, dis- 

 tally curved, slender bristles and some fine pile. On 

 the upper and posterior mesopleuron are a few scanty 

 hairs, but there is longer and somewhat more abundant 

 pile on the propleuron. Mesonotum and the whole of 

 the pleuron thinly pollinose; metanotal callosity bullose, 

 micropubescent only ; lateral slopes of the metasternum 

 pilose, ventral metasternum broadly chitinized and 

 bare; postmetacoxal area membranous. Prosternum 

 not dissociated. 



Legs : The femora are stout and only the hind femur 

 is very little swollen distally. The hind femur is 

 elongate and together with the remainder of legs 

 densely appressed setate pilose. Bristles on the hind 

 femur are conspicuous and strong; there is a single 

 ventrolateral bristle at the apical third, a pair of dorsal 

 bristles at the apical fifth, and a dorsomedial bristle 

 at the basal third, but long pile or bristly pile is quite 

 absent. Middle femur with 1 anterior bristle at the 

 outer third and 1 posterodorsal near the apex. Ante- 

 rior femur with only 1 bristle posterodorsally near 

 the apex. All the tibiae are stout, and on the hind tibia 

 are 3 long, stout, dorsolateral, 4 A'entrolateral bristles, 

 and at the apex only 5 stout bristles, of which 2 are 

 ventral, 1 lateral, the others dorsolateral and dorsome- 

 dial. On the middle and anterior tibiae bristles are 

 more numerous. There are 3 long anterodorsal, 3 short 



posterodorsal, 4 or 5 posteroventral, and 4 anteroven- 

 tral bristles on the middle pair and approximately the 

 same numbers on the anterior pair. Tarsi rather short 

 and robust, the last tarsal segment however is long and 

 with anterior and posterior fringe of 8 or 9 short 

 spinous setae. The tarsal bristles are quite long and 

 stout. Claws exceptionally long, only slightly curved, 

 sharp, the pulvilli reduced to mere stubs. The em- 

 podium is about a fourth as long as the claw. 



Wings: The wings are broad, the marginal cell is 

 comparatively widely open, but the second vein is dis- 

 tinctly recurrent, and the base of the second submar- 

 ginal cell is very strongly arched. The first posterior 

 cell is widely open, the fourth is closed with a long 

 stalk and its end vein is offset from the end of the discal 

 cell by the very short lower end vein of the discal cell. 

 Anal cell closed with a short stalk ; middle end vein of 

 the second basal cell long. Alula large; ambient vein 

 complete. 



Abdomen : The abdomen is robust, at least as wide 

 as the mesonotum, and rather elongate; the sides are 

 almost parallel to the end of the fifth segment. The 

 first tergite is nearly as long as the second and there is 

 very little difference in length among the first six seg- 

 ments. Eight tergites are present in the female, the 

 seventh and eighth nearly equal and about one-fourth 

 as long as the sixth. Abdomen densely appressed 

 setate, with scanty pollen, so that the segments are 

 mostly shining. There are stout, lateral, conspicuous, 

 tergal bristles present, 2 on each side of the first 5 

 tergites, none beyond. Female terminalia short and 

 inconspicuous, without spines, the eighth sternite with 

 a short small notch. I have seen no males. 



Distribution : Neotropical : Macahyba nordestina Car- 

 rera (1947) ; scafora Hermann (1908). 



Genus Psilocurus Loew 



Figures 57, 435, 565, 914, 923, 1667, 1671, 1928, 1957 



Psilocurus Loew, Berliner Ent. Zeitschr., vol. 18, p. 370, 1S74. 



Type of genus: Psilocurus nudiitsculus Loew, 1874, by 



nionotypy. 

 Orthoneuromyia Williston, Kansas Univ. Quart., vol. 2, p. 67, 



1893. Type of genus: Orthoneuromyia modesta Williston, 



1S93, by monotypy. 



Small or medium size flies, characterized by the dense, 

 quite short, setate pile and reduced bristles, together 

 with the open marginal cell, open first posterior cell and 

 the entirely nonrecurrent second vein. From Psilo- 

 curus the related genus Macahyba Carrera is separated 

 by the straight face, without a gibbosity, the stout and 

 emphasized oral bristles, the distinctly recurrent sec- 

 ond vein and the greatly reduced pulvilli. Length 7 

 to 12 mm. 



Head, lateral aspect: The head is of medium length, 

 the face short, on the upper half with a low gibbosity, 

 moderate in extent. The eye is strongly convex an- 

 teriorly, gently convex behind and recessive on the lower 

 fourth. The occiput very short in profile, a little more 

 prominent below, pollinose with short coarse pile ven- 



