1913] North American Dipterous Genus Neurigona 27 



16. Dorsum of the thorax with the flattened space before the scutellum black, 



gray, green, or blue 17 



Dorsum with the flattened space yellow 25 



17. Flattened space on the dorsum a beautiful greenish blue 7 signifer 



Flattened space black, gray, or dull green 18 



18. Flattened space on the dorsum and more or less of the dorsum dull green. 



19 tenuis 

 Flattened space black or gray 19 



19. Flattened space and most of the dorsum gray 22 bivittata 



Flattened space black 20 



20. Dorsum of the thorax and the black central line shining 5 nitida 



Dorsum less shining, and without distinct central line 21 



21. Dorsum with the anterior half and three stripes extending backward 



black 6 tridens 



Dorsum with only the flattened space black 22 



22. Front metatarsi only three-fourths as long as their tibiae 4 carbonifer 



Front metatarsi about equal to their tibiae 23 



23. First and second joints of hind tarsi equal 3 dimidiata 



Second joint of hind tarsi longer than the first 24 



24. Posterior cross- vein rectangular 1 rubella 



Posterior cross- vein a little oblique 2 perplexa 



25. Abdomen f asciate with black 26 



Abdomen not distinctly fasciate 27 



26. Dorsum of the thorax without black spots. Length 3 mm 12 aldrichii 



Dorsum with three black spots. Length 4.5-5 mm 8 maculata 



27. Dorsum of the thorax dull with thick yellow pollen 28 



Dorsum shining, only thinly pollenose, pollen whitish 29 



28. Dorsum evenly and thickly pollenose 11 flava 



Dorsum with pollenose vittas 18 transversa 



29. Tips of third and fourth veins widely separated 14 disjuncta 



Tips of third and fourth veins approximated 30 



30. Veins yellow 9 floridula 



Veins brownish 10 floridula var. infuscata 



1 Neurigona rubella Loew. 



Figure 1. 

 Saucropus rubella Loew, Neue Beitr., viii, p. 76, 1861; Mon. N. Am. Diptera, 

 ii, p. 226, 1864. 



Thorax and abdomen yellow, the former with the flattened space 

 before the scutellum black, the latter with black bands; hypopygium 

 black; front metatarsi about one and' one fourth times as long as their 

 tibife, with bristles below. Length 5 mm. 



Male : Face very narrow, almost linear, and with the palpi silver}^ 

 white; proboscis yellow; antennae deep yellow, the first joint paler, 

 arista yellowish brown; front and occiput black, the ground color 

 concealed by thick white pollen. Dorsum of the thorax reddish yellow 

 with the flattened space before the scutellum black and covered with 

 whitish pollen; humeri and pleurse pale yellow, the latter with white 

 pollen, and with a black spot in front of the halters; metanotum black, 

 with the sides yellowish. Abdomen yellow, dorsimi of the second, 

 third, and fourth segments with black bands, that on the second near 

 the base and narrowing at the extreme lateral edges, that on the third 

 at the base and of equal width throughout, the one on the fourth at 

 base and narrowed at the sides not reaching the lateral edges, but 

 forming a subtriangular spot; fifth segment straight above with the 

 front and hind angles square, the upper edge infuscated, and with the 



