SIMULIUM: NORTH AMERICAN SPECIES 



169 



16. Metallic bluish black species ; middle portion of fore tibiae, 



base of middle and hind tibiae, base of first and second 

 joints of middle and hind tarsi, whitish. Length 2 mm. 

 Thorax fuscous and cinereous pollinose ; the humeri pallid, 

 fore coxae pale, middle and hind ones dark ; femora pale at 

 the base, black at the tip ; tibiae black. Length 3 mm. 



17. An oblique metallic streak extending inward from each hume- 



rus ; posterior part of the thorax metallic. Length 2 to 

 2'5 mm. . . . . 



Humeral spots not metallic . ' . 



18. Anterior coxae yellow; long hair on femora and hind tibiae; 



thorax velvet black with white pruinose margin (Greenland) 

 Anterior coxae black . . 



19. Thorax velvet black, with oblique cinereous humeral spots, 



and usually two tiny metallic spots between them. Length 

 3 to 4 mm. . . . . , 



Thorax velvety black with two very narrow grey stripes and 

 posterior margin ; hind tibiae usually yellow at the base, 

 hair on legs sparse ........ 



20. Thorax striped \ .' , 



Thorax without stripes ........ 



21. Dorsum of thorax with four longitudinal lines, posterior margin, 



white pollinose ; abdomen opaque black. Cuban species . 

 Not with four stripes . . . . 



22. Dorsum of the thorax with five stripes, the outer ones spot- 



like, the intermediate ones clubbed at the ends ; abdomen 

 with black fascia on each segment, produced posteriorly 

 at the middle and the ends. Sometimes the last few seg- 

 ments have only three or five spots ..... 

 Thorax with one or three stripes ...... 



23. With three stripes ........ 



' With an indication of a darker median vitta ' (see 31) . 



24. Small species, length about 1'5 mm. 'Abdomen silvery, 



third and fourth segments wholly brownish, sometimes 

 with a median spot on each; legs yellowish, tarsi blackish 

 or brownish '. Species from Texas 



Larger species 3 mm. or more in length .... 



24a. Middle tibiae brown with a yellow ring beyond the base ; 



vittae of mesonotum brownish, the median vitta dilated 



posteriorly, wider than either of the lateral .ones.. New 



Mexico . . . 



Femora and tibiae greyish, sometimes quite pale, tips of tibiae 

 black. Latero-dorsal thoracic stripes clubbed at the anterior 

 end. Third, fourth, fifth, and part of sixth and seventh 

 abdominal segments with velvet black fasciae ; centre of 

 6, 7, and 8 greyish or dull brown . 



25. Abdomen without distinct black spots .... 

 Abdomen spotted . . . . . . . 



26. Abdomen black, covered with long yellow pile ; legs yellow, 



the tips of the femora and tibiae, and all the tarsi except 

 basal two-thirds of the hind metatarsi, brown . . 



Abdomen nearly bare ....... 



22 



metallicum. 



cmereum. 



venustum. 



reptans. 



18 



19 



pictipes. 



vittatum. 



21 

 25 



quadrivittatum. 



22 



vittatum. 



32 

 24 



griseum. 



tamaulipense. 



. 24a 



virgatum. 



pictipes. 



bracteatum. 



26 

 31 



27 



