NO. 1710. NORTH AMERICAN DRAG0NFLIE8— WILLIAMSON. 377 



tibial keel of middle tibia and abdominal markings mentioned above. 



1 have collected all the specimens I have seen but two. Until this 

 study was begun I confused this species with illinoiensis, and I recall 

 nothing striking in its habits in life. 



Types. — Male and female in author's collection, taken at Ohiopyle, 

 Pennsylvania, June 24 and June 25, 1900, respectively. 



Material ^xa/mw(Z.— Dunbrooke, Virginia, July 31, 1899, male, 

 R. P. Currie (U.S.N.M.). Ohiopyle, Pennsylvania, June 24, 1900, 



2 males, E. B. Wilhamson. June 25, 1900, 2 males, 1 female, E. B. 

 Williamson (1 male P. P. C). June 26, 1900, male, E. B. Wilhamson 

 (U.S.N.M.— Insect Book, pi. 42, fig. 7). September 8, 1901, female, 

 J, L. Graf. Livingston, Kentucky, June 23, 1904, male, E. B. Wil- 

 liamson. A damaged female, collection C. C. Adams, Cleveland, Vir- 

 ginia, August 4, 1899, probably is this species. Total, 7 males, 2 

 females. 



MACROMIA ILLINOIENSIS Walsh. 



Length of abdomen: Male, 47-52 mm.; average, 48.8; female, 

 47-51 mm.; average, 49. Length of front wing: Male, 42-45.5 mm.; 

 average, 44.1; female, 46-50 mm.; average, 48.2. Length of hind 

 wing: Male, 40-45 mm.; average, 42.4; female, 45-49 mm.; aver- 

 age, 47. Length of first tibia, male, 7 mm.; hind femur, male, 10.7 

 mm. Length of tibial keel in length of tibia, male: First tibia. ^; 

 middle tibia, ^ — to ^." 



Without trace of antehumeral thoracic stripe. Latero-ventral 

 metathoracic carina brown. Yellow ring on abdominal segment 2 

 narrow and interrupted at the auricles and dorsum to form 4 spots. 

 Costa dark. 



Male. — Postclypeus distinctly paler, clearer in color than the 

 labrum; dorsal spots on frons variable in size, always small, about 

 0.5 mm. in diameter, and about half as large as the lateral spots; in 

 one specimen dorsal spots are entirely wanting. (There is consider- 

 able variation in the coloring of the labrum, especially in the extent 

 of marginal and central black or dark brown, but this seems inde- 

 pendent of locality). 



Abdominal spots on 3-6 never meeting in the median line, growing 

 smaller posteriorly, present in only 2 cases on 6, and frequently 

 absent on 4-6; present on 7 as a large dorsal basal spot, posteriorly 

 reaching the transverse carina on either side, produced briefly pos- 

 teriorly in the mid-dorsal line, not encircling the segment, but limited 

 beneath on the sides by black; segment 8 with a small, narrow, trian- 

 gular basal spot on either side, the bases of the triangles narrowly 

 separated by the middorsal black line, variable in size and often 

 reduced to mere traces; 8 and 9 (rarely 7) ventrally each with a basal 

 yellowish spot on either side. 



a Very rarely shorter; I have examined 2 specimens in which it is f . 



