March, 1917] CoLE : OsTEN SaCKEN's GrOUP " POiCILANTHRAX." 71 



Anthrax arethusa O. S. (figs. 11 and iia). 



Anthrax arethusa O. S., Biologia, Dipt., i, 116. 



" A series from Central America and Mexico resemble halcyon in 

 having their third posterior cell bisected, but show a marked differ- 

 ence. A. halcyon has a more northern distribution. The sides of 

 the abdomen of halcyon beset with yellow pile, but on the distal half 

 of the segments, beginning in most specimens with the third, there 

 is a tuft of black pile. The bisecting cross vein is often wanting 

 from both wings, sometimes from one wing only. 



"Arethusa differs from halcyon: Abdomen red on the sides on all 

 segments; the black forms a broad stripe in the middle, occupying 

 all of the first segment, and is gradually attenuated posteriorly. On 

 the seventh segment the black occupies but a small spot in the middle. 

 The wings are narrower and paler; the interval between the hyaline 

 spot in the discal cell and the posterior margin is almost altogether 

 hyaline, crossed by two veins the second of which is more or less 

 clouded; the cross vein bisecting the third posterior cell is differently 

 placed; in halcyon it connects the end of the discal cell with the in- 

 tercalary vein, and the stump does not come in contact with it; in 

 arethusa it connects the intercalary vein with the stump, so that the 

 latter seems to issue from the curve of the cross vein; in some cases 

 the end of the stump disappears, and then the convex cross vein 

 remains. 



" In both species the subhyaline spot commonly occurring in 

 species of Anthrax near the proximal end of the discal cell is nearly 

 obsolete ; in this they differ from paxilogaster. 



" In size the average arethusa is a little smaller and narrower 

 than halcyon. I have six specimens from Guatemala City, five from 

 Irazu, two from N. Sonora, two from Presidio and one from Orizaba. 

 A specimen from Manitou, Colo. (Aug. 17, 1876), seems to belong 

 here, it is larger, the black dorsal stripe of the abdomen is remark- 

 ably narrow, and the tufts of black hair on the sides of the abdomen 

 consist of a few hairs only, hardly visible among the yellow hairs." 



Anthrax arethusa var. autumnalis new variety (fig. 8). 



This species answers the description of arethusa very well, but does not 

 have the supernumerary cross vein bisecting the third posterior cell. The 

 specimens in my collection are very close to willistoni Coq., in general appear- 

 ance and wing markings. The venter is pale reddish. The specimen figured 



