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UNITED STATES NATIONAL MUSEUM BULLETIN 224 



Genus Thereutria Loew 

 Figubes 97, 576, 1165, 1174, 1748, 1811, 1904, 2019 



Thereutria Loew, Bemerkungen iiber die Familie Asiliden, 

 1851, p. 20, 1S51. Type of genus: Laphria amaracus 

 Walker, 1849, as Thereutria calcar Loew, 1851, by monotypy. 



Scandon Walker, Insecta Saundersiana, vol. 1, pt. 2, p. 108, 

 1851. Type of genus: Scandon compactus Walker, 1851, 

 by monotypy. 



Flies of medium size, easily recognized by the combi- 

 nation of the closed marginal cell and the presence of 

 the protibial spur, without accompanying flange upon 

 the basitarsus. Females have acanthophorites with 

 spines. The known species are dark colored, bare, 

 feebly shining flies with the tibial, thoracic and cephalic 

 bristles strongly developed. The male terminalia is 

 not rotate. These flies are probably distantly allied to 

 Saropogon Loew and perhaps connect the Stenopogon 

 Loew and Saropogon groups. Length 12 to 18 mm. 



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

 The face is short, except on the lower third where there 

 is a small, rounded elevation or gibbosity. The occiput 

 is prominent throughout its height except immediately 

 behind the upper eye margin. The pile of the occiput 

 is fine, long and dense on the lower third and is wholly 

 replaced by bristles on the upper two-thirds ; upon the 

 middle third the bristles are situated in 2 or more rows ; 

 The proboscis is comparatively short but extended well 

 beyond the face, with a high, medial ridge which is at- 

 tenuate and reduced shortly before the apex leaving the 

 apex quite pointed, dorsoventrally flattened and shovel- 

 like. Apical third on either side below with long, 

 slender, bristly hairs and still longer hairs on the basal 

 half. Palpus large and clearly of two segments; the 

 first segment is excavated and bears long, ventral pile ; 

 the second is clavate with an apical pore and scattered, 

 slender bristles on all sides. The antenna is attached at 

 the upper third of the head and is very little longer 

 than the total head length. The first segment bears 4 

 or 5 long, stout, ventral bristles and is subequal in 

 length to the second segment with 2 or 3 similar bristles. 

 Third segment elongate, comparatively slender, slightly 

 narrowed near the base and again at apex; it bears 

 traces of a completely fused microsegment. At the 

 apex there is a wide, truncate pit and spine. 



Head, anterior aspect : The face at antenna is about a 

 fifth the head width or less, and slightly wider below. 

 The face cover consists of dense pubescence without 

 pile and with a narrow, supraepistomal band or cluster 

 of stout, rather long, scattered, often pale bristles. 

 Subepistomal area large and oblique. Front consid- 

 erably wider than the face, becoming again reduced or 

 convergent to a moderate extent at the vertex. The 

 front is somewhat sunken, densely pollinose and bears a 

 characteristic row of strong, close-set bristles on each 

 eye margin. There may be a single bristly hair in the 



middle of each half of the front. The vertex is shal- 

 lowly excavated, the ocellarium low and wide with 5 

 pairs of long, slender bristles and a low-set, submedial, 

 postvertical cluster of 4 stout bristles on the upper 

 occiput. Anterior eye facets rather strongly enlarged. 



Thorax: The mesonotum is thinly pollinose with 

 greatly reduced pile consisting of a few scattered, 

 bristly hairs on the humerus, behind the humerus and 

 above the wing. There is a well developed single row 

 of acrostical bristles, short and fine, a single row of 

 long, more stout dorsocentral bristles. The comple- 

 ment of long, prominent, lateral bristles is as follows: 

 1 humeral, 2 notopleural, 3 supraalar, 2 postalar, 2 pairs 

 of bristles on the scutellar margin. Propleuron with 

 a row of weak bristles on the pronotum and 2 laterally 

 on the pronotum; lateral elements of the propleuron 

 with a dense, conspicuous tuft of fine, long pile. Pro- 

 sternum dissociated. Upper sternopleuron with a tuft 

 of long, fine pile. Mesopleuron, pteropleuron and hy- 

 popleuron apilose. Metapleuron with a vertical row of 

 6 or 7 long, stout bristles and some pile. Metanotal cal- 

 losity very strongly swollen and pubescent only. 

 Scutellum flat, pollinose, without pile. Postmetacoxal 

 area membranous; lateral and ventral metastemum 

 with scattered hairs. 



Legs : All the femora are stout without being swollen 

 and bear rather dense, fine, appressed setae and very 

 few bristles. Hind femur with a single, stout, lateral 

 bristle at the basal third only. Anterior and middle 

 femur each with a similar bristle posteriorly near the 

 apex. Tibial bristles few but quite stout and con- 

 spicuous ; their pile is comparatively fine and appressed. 

 On the hind tibia are 3 dorsomedial, 3 dorsolateral and, 

 beyond the middle, 2 ventrolateral bristles. The apical 

 cluster consists of 7 bristles, of which 1 is dorsal and 2 

 are medial. On the middle tibia are 4 anterodorsal 

 bristles, the last 2 of which are exceptionally long and 

 stout, 4 posterodorsal, 4 posteroventral, and 2 very long, 

 ventral bristles. Anterior tibia with the dorsal bristles 

 on either side small and consisting of 4 in each row, 5 

 weak posteroventral bristles, supplemented by 2 ex- 

 ceptionally long, stout, ventral bristles directed back- 

 ward. In addition there is a ventral row of 8 long, 

 bristlelike hairs. Apex with a rather stout, twisted 

 spine ; a basal protuberance is lacking or short. Claws 

 sharp, pulvilli well developed, and empodium flattened. 



"Wings: The wings are slender, the marginal cell 

 closed and stalked; all the posterior cells are widely 

 open, and the anal cell is open. Alula present, ambient 

 vein complete. 



Abdomen: The abdomen is comparatively robust 

 basally and rather strongly tapered in females beyond 

 the third segment and more gently tapered in the males 

 beyond the first segment. Bristles are restricted to 

 the first tergite, where there may be as many as 6 quite 

 stout bristles. Pile greatly reduced, fine and scattered 

 laterally, short, appressed and setate on the dorsal por- 



