571 



gills. The lateral setae of the labium do not often exceed five, whereas 

 there are usually six in vcrticalis. 



Adult; Male. — Color, black and sulphur-yellow. 



Head black and yellow; mouth-parts buff, the median lobe sub- 

 triangular; palpi narrow, the distal segment pale; antennae uniform 

 dark brown, the second segment considerably longer than the first; 

 postclypeus shining black ; anteclypeus pale, labrum pale, with a trans- 

 verse dorsal black stripe which has a slight ventral projection on the 

 meson; remainder of the labrum, exposed portions of the mandibles 

 and their trochantins, genae, and the front dorsad of the fronto-clvp- 

 eal suture to the level of the antennal fossae, shining yellow; re- 

 mainder of the front and vertex black, the postocular spots yellow and 

 circular ; a- short yellow line caudad of the ocelli ; postgenae and occiput 

 yellow. 



Thorax black and yellow ; pronotum black except the cephalic 

 lobe, which is yellow; caudal lobe with yellow spots on the lateral 

 angles ; mesostigmal plates with large oval yellow spots ; mesosupra- 

 episterna with short yellow stripes and spots adjacent to the parap- 

 tera, the two together forming an exclamation point on each side of 

 the dorsal carina ; black stripe covering the mesopleural suture on 

 each pleuron contracted near the wing bases; dorsal half of the mes- 

 infraepisterna and a stripe on the metapleural sutures black, the re- 

 mainder of the metathorax and the -postcoxal areas yellow ; legs black 

 and yellow, the coxae, trochanters, and femora pale, the femora with 

 a dorsal stripe on each from base to apex, the stripe widened subapi- 

 cally; tibiae with a dorsal black stripe from base to apex which fades 

 into brown towards the apex ; tarsi and claws pale, darker at the tips ; 

 wings short, the postnodal cross-veins six to eight and M 2 arising 

 between the third and fourth postnodal cross-veins in the front wing 

 and between the second and third in the hind wing. 



Abdomen black and yellow; terga i-io dull black with the excep- 

 tion of a narrow basal ring on segments 3-7, the stripes narrowed 

 conspicuously on two and widened on the apices of segments 3-6 

 inclusive ; lateral margins of all terga pale yellow ; sterna 3-8 lined 

 with black on the meson; apex of the tenth tergum with a mesal eleva- 

 tion at the apex, the elevated portion forming two small tubercles; 

 anal appendages (Figs. 173,177) small, orange, the superiors large 

 and blunt and bent ventrad, the inferiors also large, blunt, and bifur- 

 cate, the arms feebly divaricate and the dorsal arm with a number of 

 heavily chitinized teeth. 



Female. — Color, pale blue and black. 



Head similar to that of the male except that the postocular spots 

 are blue. 



