ANTHEAX. HT 



northern distribution. I have seen specimens from different localities between British 

 America and Colorado. It has been very well described by Say, Long's Exped. ii. p. 371. 

 In Wiedemann's description (Aussereur. zweifl. Ins. i. p. 288) the statement " vom 

 dritten Abschnitte an sind die Seitenrander schwarzbehaart " must not be taken literally : 

 the sides of the abdomen are beset with yellow hair, but on the distal half of the 

 segments, beginning in most specimens with the third, there is a tuft of black pile ; 

 in some specimens there are some black hairs on the sides of the second segment also. 

 Wiedemann's other statement—" in der Mitte des Hinterleibes haben die Abschnitte 

 am Hinterrande einen breit dreieckigen Fleckhen ohne gelbliche Behaarung "—does not 

 apply to well-preserved specimens. That Wiedemann had the true A. alcyon, Say, is 

 proved by the figure of the wing which he gives, and which shows the characteristic 

 bisection and stump in the third posterior cell (I. c. t. 3. f. 6.) The bisecting cross- 

 vein is often wanting from both wings, sometimes from one wing only. 



A. arethusa differs from A. alcyon in the following principal characters : — The abdomen 

 is red on the sides on all segments ; the black forms a broad stripe in the middle occu- 

 pying the whole breadth on 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 lighter in colour; 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 A. alcyon it connects ^ ^ ^ g ^ ^ 

 the end of the discal cell with the intercalary vein, and the lg ' ' ^' ' 8 ' 

 stump .does not come in contact with it ; in A. arethusa it ](. J^ L 

 connects the intercalary vein with the stump, so that the J \ \ 



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 alone 

 remains (see the annexed woodcut, fig. 1, A. alcyon, figg. 2 and 3, A. arethusa. 



In both species the subhyaline spot commonly occurring in the species of Anthrax 

 near the proximal end of the discal cell is nearly obsolete ; in this they differ from 



A. poecilogaster. 



In size the average A. arethusa is a little smaller and narrower than A. alcyon. I 

 have before me six specimens from Guatemala city, five from Irazu, two from Northern 

 Sonora, two from Presidio, and one from Orizaba {coll. Bellardi). A specimen 

 which I took at Manitou, Colorado, August 17, 1876, also seems to belong here ;. 

 it is larger than the average A. arethusa, the black dorsal stripe of the abdomen is 

 remarkably 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. 



N.B.— Say wrote alcyon, Wiedemann halcyon ; both Alcyone and Halcyon occur in 

 the classics : alcyon, being the original spelling of Say, is perhaps preferable. 



A. alcyon, Macq., Dipt. Exot. ii. 1, p. 68, t. 19. f. 7, is certainly not Say's species, 

 but A. ceyx, Loew. 



