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UNITED STATES NATIONAL MUSEUM BULLETIN 224 



FAB! I 



Text-Figure 12 — Pattern of distribution of the genus Microstylum Macquart. 



by bristles or may be abundant. The proboscis is un- 

 usually long, characteristically directed straight for- 

 ward, almost always strongly compressed, but sharply 

 pointed at the immediate apex which is actually de- 

 pressed dorsoventrally ; in one group this depression 

 may be carried all the way to the base. Proboscis is 

 rarely subtriangular or subcylindrical. The apex has 

 a few fine hairs, the base usually with no pile and rarely 

 with a few fine hairs ventrally in the middle ; a ventral 

 groove is present ; a dorsal ridge may be absent, exten- 

 sive, very low, or well developed at the base. Palpus 

 large, conspicuous, clearly of two segments, the first is 

 hemicylmdrical and excavated and the second elongate, 

 cylindrical, densely bristly except medially ; the second 

 segment is not porate; apical bristles are present. 



Antenna attached just above the upper third of the 

 head; the first two segments are relatively short and 

 nearly equal in length, sometimes the second segment 

 a little longer than the first. The third segment is 

 slender, basally attenuate, begins to be moderately swol- 

 len or widened at the basal or middle third and its usual 

 length is iy 2 times the combined length of the first two 

 segments; carries at its apex a short, usually truncate 

 microsegment with, in turn, an apical spine. Pile of 



first segment, composed of short, stiff, subappressed 

 setae, second segment with similar, but longer, stiff 

 setae or sometimes with 1 to 3 quite long, stout, ven- 

 trolateral bristles. 



Head, anterior aspect: The face below antenna is 

 about one-third the head width or less and divergent 

 below. Subepistomal area large, deeply concave, bare 

 and strongly oblique. Face micropubescent, apilose ex- 

 cept on the subepistomal margin; lower third of face 

 sometimes with pile. Mystax almost always confined 

 to a single row of very stout, long, epistomal bristles, 

 most generally 4 pairs, but often with 1 or 2 additional, 

 shorter, more slender bristles present, and frequently 

 with considerable, short, stiff, intermixed pile. Very 

 rarely does the mystax extend over the entire lower 

 third of the face. Front short, with lateral pile only, or 

 more commonly with bristles which may be present in 

 a single subocular row or a rather wide band of many 

 such bristles. Vertex very little excavated, the ocella- 

 rium low but prominent and bearing between the 

 posterior ocelli 1 or 2 pairs of short, stiff bristles and 

 several pairs of additional bristles irregularly placed 

 beyond the ocelli, or sometimes none in the intraocellar 

 area. Again, the ocellarium may have a lateral row of 



