12 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 6t> 



d^. Discal scutellar bristles but little smaller than the lateral basal 

 pair, and forming with them a strong curve ; female with two 

 pairs of orbitals, just outside the frontal row, which is here very 



hairlike ( Peru ) cruciata Townsend. 



c". Femora, pleurae, and base of abdomen yellow. 

 (f. One pair anterior acrostichals. 



e\ Posthumeral 1 (Panama) tibialis Aldrich. 



e^. Posthumeral 2 (South America) aeneiventris Wiedmann. 



d^. No anterior acrostichals. 



e^. Mesonotum viewed from behind shows three dark stripes, sepa- 

 rating four pollinose ones (Brazil) purpurata Aldrich. 



e^. Viewed from beliind the pollen is not distinctly divided into 4 



stripes (Costa Rica) semiflava, new species. 



h\ Fourth abdominal segment without discals. 

 c\ Facial ridges high and sharp, hairy to middle ; middle and hind tibiae 



not at all infuscated ; sternopleurals 2, 1 facialis Aldrich. 



cl Facial ridges lower, not hairy except close to vibrissae. 

 d'. With 1 or 2 pairs of anterior acrostichals. 

 e^ Legs, pleurae, and base of abdomen largely yellow. 



f. Second to fourth abdominal segments with a posterior sharply 

 defined violet band ; third segment without marginal bristles 



(Brazil) cyaneicincta Surcouf. 



f. Second to fourth abdominal segments not banded with violet ; 

 third segment with row of marginals (Costa Rica). 



flavicrura, new species, 

 e*. Legs, thorax, and abdomen bluegreen or blackish ; fifth sternite 

 of male produced in two shining black styles (Costa Rica). 



spicata, new species. 

 (Z^ Without anterior acrostichals. 

 e^. Only one intra-alar (the posterior) ; abdominal segments 2-4 

 with sharply defined posterior violet bands (Brazil). 



pauciseta Aldrich. 

 e^ With 2 intra-alars ; abdomen not violet-banded. 



f. Second abdominal segment with only weak hairs along hind 



margin (South America) randa Walker. 



f. Second abdominal segment with a distinct row of marginal 

 bristles. 

 g^. Middle and hind tibiae black, in male the middle ones elon- 

 gated and with only minute bristles (South America). 



quadrilineata Fabricus. 

 g*. Middle and hind tibiae not or hardly infuscated; male with 

 the usual bristles on middle tibiae (Brazil). 



dorsimacula Aldrich. 

 A'. Stem-vein ciliated behind (subgenus Mesembolia Aldrich). 



a\ Greatest width of apical cell exceeding the length of the hind crossvein. 



b\ Apical cell moderately wide open, the included costal segment not more 



than half the preceding one; no acrostichals immediately behind the 



suture (Mexico to Paraguay) bellardiana Aldrich. 



h'. Apical cell very wide open, the included costal segment more than half 



the preceding (Brazil) fulvipes Aldrich. 



a: Greatest width of apical cell less than hind crossvein (Brazil). 



peregrina Aldrich. 



