400 



UNITED STATES NATIONAL MUSEUM BULLETIN 224 



subapical hairs. The antenna is attached at the upper 

 third of the head, the first two segments are equal in 

 length and each has around the middle a circlet of 

 setae; these wanting on the medial surface. One of 

 the ventral elements on the first segment forms a mod- 

 erately long bristle. Third segment straight, no wider 

 than the second and not over 1% times the combined 

 length of the first two. It lias attached at the apex a 

 short, somewhat spoonlike microsegment bearing at 

 the base a minute, exposed, dorsal spine arising from 

 the end of the third segment. The microsegment bears 

 a slightly longer micropubescence. 



Head, anterior aspect: The head is of moderate 

 width, about one and three-fifths times as wide as high. 

 Face beneath the antenna about one-fourth the head 

 width and slightly narrowed below. It bears on each 

 side 2 or 3 long, slender bristles confined to the upper 

 half of the face and on the lower face above the epis- 

 toma on each side a vertical row of 2 slightly longer, 

 slender bristles and 2 bristles almost as long bordering 

 the upper part of the lateral epistomal margin. There 

 are also a few fine hairs ventrally. The face cover 

 consists of scanty, flattened pubescence which is quite 

 flat appressed. Front distinctly wider than the upper 

 face, with lateral, shallow grooves continued behind 

 the ocelli. The ocular slope has 5 or 6 medium long 

 bristles, one of which is at the vertex ; the medial slope 

 has pollen only. Ocellarium rather large, with nearly 

 vertical sides and bearing 1 pair of long, moderately 

 stout bristles and behind the ocelli sometimes a pair 

 of minute bristles. 



Thorax: The mesonotum is comparatively small and 

 short, shallowly convex and sparsely covered with mi- 

 nute, curled, appressed pile on a polished, shining 

 background. The pile arises from punctures so small 

 as to be inconspicuous ; also the pile is quite undiffer- 

 entiated. The bristles are quite small and consist of 

 1 on the notopleuron, 1 supraalar and 1 postalar, and 

 none on the scutellum. Scutellar disc flattened, rugose, 

 with minute, curled setae and the rim slightly emargi- 

 nate. Metanotal callosity with a patch of short bristles. 

 Propleuron quite short, the pronotum with fine pile. 

 Mesonotum bare and polished and not punctate; stri- 

 ate, with the upper border pollinose, and a minute, pos- 

 terodorsal, bristly hair. Metapleuron with a vertical 

 row of 4 long, slender, black bristles ; presternum fused, 

 postmetacoxal area with a narrow band of chitin behind 

 the posterior coxa. 



Legs: The hind femur is rather stout and a little 

 swollen, especially beyond the middle. The legs are 

 polished and bare, with almost no pile and a few setae. 

 The bristles on the femora are few, for the most part 

 minute, and more slender and longer on the tibia. 

 Hind femur with a partly doubled, dorsolateral row of 

 10 or 11 rather minute bristles, longer distally. On 

 the ventral aspect are about 8 sharp spines of no great 

 length; these might be described as either spines or 

 spinous bristles. The lateral surface of hind femur 

 with a number of short, stout, scattered, spinous setae. 

 Hind tibia with 7 dorsolateral setae, 3 dorsomedial setae 



and other smaller elements, and dorsolaterally beyond 

 the middle and at the apex also 1 conspicuous bristle 

 of no great length; there is a smaller bristle ventro- 

 laterally on the outer fourth. Ventral surface of this 

 tibia with rather dense, fine, erect, pale pile which is 

 absent on the basal third. The femur also has similar 

 ventromedial pile but less dense. Hind basitarsus much 

 more slender than the comparatively stout tibia. It is 

 nearly as long as the three short succeeding segments. 

 Middle femur with 2 or 3 weak bristles on each side 

 dorsally near the apex, 1 bristly hair ventrally near the 

 base and some other stiff, erect, short, ventral hairs. 

 This tibia bears 2 long, slender, anterior bristles at the 

 middle and beyond, a shorter bristle near the apex and 

 several short bristles near the base. There are also 2 

 quite slender, long, ventral bristles but posterior ele- 

 ments are lacking. Anterior femur rather similar to 

 the middle pair, the anterior tibia with several long, 

 quite slender posterodorsal and posteroventral bristles, 

 2 above and 2 below, and 7 short bristles or setae an- 

 teriorly. Tarsal bristles long; claws slender, sharp, 

 bent at apex; pulvilli long and slender; empodium 

 slender, swollen at the base. 



Wings : The wings are broad, tinged with pale brown, 

 entirely villose. Marginal cell closed with a short 

 stalk. Base of second submarginal cell quite wide, ex- 

 panded entirely anteriorly. First posterior cell fully 

 open, fourth posterior cell closed with a long stalk, and 

 the anal cell closed and stalked. Posterior crossvein 

 long, the anterior crossvein enters the discal cell beyond 

 the middle. The medial crossvein is almost eliminated 

 so that the vein closing the fourth posterior cell almost 

 meets the upper section of the anterior intercalary vein 

 but is not aligned with it; this varies to some extent. 

 Alula quite narrow; ambient vein complete but weak 

 basally. 



Abdomen : The abdomen is broadly oval with a some- 

 what flattened appearance especially down the middle 

 and more convex laterally. The first four segments 

 are nearly equal in width in females; the first segment 

 is rounded off anteriorly towards the sides and the 

 last two segments more or less triangular taken to- 

 gether. The abdomen is fully as wide as the thorax 

 and bears moderately abundant, minute, quite flat ap- 

 pressed setae or setate pile. Only the first segment 

 anteriorly bears a few lateral, not appressed hairs. 

 This segment also has at the sides 2 or 3 moderately 

 stout, black bristles and a few, erect, yellow setae. The 

 first segment is as long or almost as long as the second 

 and the third to fifth segments are of equal length; 

 the sixth is almost as long as the fifth and in females 

 the seventh segment is shortly exposed dorsally and 

 pale yellow in contrast to the shining black abdomen. 

 Eighth segment fully concealed. The whole abdomen 

 is densely covered with minute punctures. 



Distribution : Neotropical : Rhathimomyia nitidida 

 Lynch Arribalzaga (1882). 



I have had for study 2 females loaned by the Hope 

 Department Entomology, Zoological Museum, Oxford 

 University, winch I believe are correctly identified as 



