26 AMERICAN BLACK FLIES OR BUFFALO GNATS. 



8. Stripes on scutum curved, the outward extremities of dorso-lateral 



pair dilated; legs with a narrow black or brown ring or spot near 

 l)Mse of tibia' in addition to the usual dark marks present on the legs 



in most species virgatum, i». 58. 



Stripes on scutum straight, legs with the bases of tibise pale, and with- 

 out a subbasal dark band 9 



9. Stripes on scutum not sharply defined, the central black stripe broad at 



anterior extremity, linear ou disk, the outer black stripes short and 

 narrow glaiicum, p. 60. 



Stripes on scutum generally sharply defined, the black always broader 



than the white stripes rittuttim, p. 54. 



10. Only two posteriorly incurved, elongate spots on anterior margin ; fore 



tarsus distinctly dilated veniintinn, p. 44. 



In addition to the two spots just mentioned, there are sometimes jires- 

 eut two smaller spots on the anterior margin nearer to center and 

 occasionally also faint indications of a central bifid striiie ; fore 

 tarsus veiy slightly dilated pictipes, p. 56. 



I have not seen the males of Simnlmm metallicum Bellardi, S. cin- 

 ereum Belhtrdi, nor S. 7nexicanum Bellardi, but translations of the 

 original descriptions are given under the descriptions of these species. 



SPECIES GROUPS IN SIMULIUM LATREILLE (fEMALES). 



1. Mesopleura with a group of hairs in addition, and anterior to the normal 



pleural tuft Group A, p. 26. 



Mesopleura bare except for the pleural tuft 2 



2. Yellow species; scutum with brown, or white longitudinal stripes, or 



two discal elongated spots; abdomen and legs with black or brown 



marks Group B, p. 29. 



Black or gray species, scutum and abdomen never yellow (cf. gns€nm)_ 3 



3. Scutum with three, or five stripes, or only one central stripe, either black 



or brown on a gray ground, or metallescent pollinose on a black 

 ground, the dorso-lateral pair, when present, distinctly curved, and 



dilated at anterior extremities Group D, p. 47. 



Scutum with two, or four broad, white, straight, or very slightly curved 

 stripes, which are nearly parallel-sided and not noticeably dilated at 

 anterior extremities, or scutum unstriped 4 



4. Scutum unstriped or with only very slight indications of a central, 



darker, divided stripe Group C, p. 34. 



Scutum distinctly striped, the stripes white or metallescent polli- 

 nose Group E, p. 61. 



It is not the intention of the writer to indicate from the above 

 arrangement that these groups are entitled to treatment as sub- 

 genera ; the purpose in separating them thus is merely to facilitate 

 the work of identification of the species. 



GROUP A. 



Species with hairs on pleurae in addition to and anterior to the 

 pleural tuft. 



