ROBBER FLIES OF THE WORLD 



457 



Text-Figure 32. — Pattern of distribution of the genus 

 Akivius Loew. 



Genus Alcimiis Loew 



FiGXJBES 387, 717, 1417, 1426, 2272, 2326, 2475, 2476 



Alcimus Loew, Linnaea Entomologica, voL 3, p. 391, 1848. Type 

 of genus : Trupanea longipes Macquart, 1838, by monotypy. 



Large, elongate, and slender flies, the abdomen longer 

 than the wing, cylindrical but strongly tapered. The 

 wings are exceptionally long and slender; pilosity is 

 greatly reduced. These flies are also characterized by 

 the short face and the elongate hind legs, distinctly 

 longer than the abdomen. There are three submarginal 

 cells present and the crossvein between the branches of 

 the third vein is placed very close to the point of origin 

 of the anterior branch. Length 25 to 40 mm. 



Head, lateral aspect: The face is slightly produced 

 on the upper half, a little more prominent at the base 

 of the antenna; the lower portion of the face is quite 

 plane and pei-jDendicular and more conspicuous below 

 due to a marked posterior recession of the eye. Com- 

 bined with a slight, narrow, anterior eye recession this 

 gives the eye below a narrowed, pinched appearance. 

 Occiput thick and extending in almost equal thickness 

 up to or close to the vertex; the pile is moderately 

 abundant above and in the middle and consists of about 

 6 weak elements followed above by 12 exceptionally 

 stout, barely curved bristles. The proboscis is rather 

 small, and subcylindrical, with a bkmt apex, which is 

 tapered chiefly from below and bears stiff, apical pile; 

 a dorsal ridge is absent ; there are numerous, long hairs 

 at the base below. Proboscis directed obliquely down- 

 ward. Palpus of one segment with a close-set tuft of 



535914— 62— pt. 2 3 



long, downwardly curved, slender, apical bristles and 

 fine, ventral, lateral and dorsal pile. The antenna at- 

 tached just below the upper third of the head; the first 

 segment is at least twice as long as the second and these 

 two are approximately equal to the third segment in 

 length. Third segment only slightly wider than the 

 second; it is gently tapered from the middle to the 

 blunt apex and bears a short style only a little longer 

 than the third segment; no microsegments present. 

 The apex of the style bears a minute spine. First seg- 

 ment of antenna with 10 to 12 appressed setae above 

 and a row of 3 long, stout, oblique bristles below. 

 Second segment with 4 short setae above, 3 shorter 

 bristles below. 



Head, anterior aspect : The face below the antenna is 

 a little less than two-sevenths the head width, slightly 

 expanding below. Subepistomal area small, deeply 

 concave and pubescent. The face is pubescent, with 

 stiff, strongly curved, abundant pile on the upper half, 

 some of which might be considered weak bristles. 

 Weak, longer bristles are present below the middle and 

 there are 5 pairs of exceptionally long, stout bristles 

 along the middle of the upper epistomal margin; the 

 lateral margin bears 2 to 4 additional pairs of bristles. 

 The front is slightly divergent, the vertex slightly con- 

 vergent; the front has 3 subocular bristles and below 

 it laterally a patch of long, stiff pile. Vertex deeply 

 excavated with slantmg sides. Ocellarium moderately 

 large with 2 pairs of short, slender bristles. Eyes with 

 the central facets enlarged. 



Thorax : The mesonotum laterally, together with the 

 pleuron, is pollinose, but the middle of the mesonotum 



