NO. 1710. NORTH AMERICAN DRAOONFLIES— WILLIAMSON. 



379 



postrigonal cells, as well as other areas, female Macromias have a 

 larger number of cross- veins than the males). (See fig. 6.) 



Vulvar lamina about |-i length of segment 9, deeply and widely 

 emarginate in a semicircle or right angle. Abdominal appendages 

 equal or very slightly shorter than segment 10. 



I refer to illinoiensis two very similar males, one from Great Falls, 

 Maryland (U.S.N.M.), and the other from Pennsylvania (Acad. Nat. 

 Sci., Phila.). These have abdomen 51 mm. in length and hind wing 

 46. The Maryland specimen has the tibial keels as usual in illinoiensis, 

 but in the Pennsylvania specimen the keels of the first and middle 

 tibiae are J + and J in length of the respective tibiae. The abdominal 

 spots on 3-6 are conspicuous, those on 6 in the Maryland specimen 

 being about 1 mm. in diameter, and in the Pennsylvania specimen 

 about half as large. It is possible that a larger series would reveal 

 that these 2 specimens are specifically distinct. 



Fig. 6.— Wings of female Macromia illinoiensis, Sandusky, Ohio, July 12, 1903. 



M. illinoiensis is the best known and most widely distributed of the 

 North American Macromias. Professor Walker, who has observed the 

 species carefully, has written me with reference to its habits, and his 

 remarks are quoted in full: 



I have taken the species in but two localities, De Grassi Point, Lake Simcoe, and 

 Go Home Bay, Georgian Bay (both Ontario, Canada), but I have also seen it on the 

 wing on the North River, Algonquin Park, where I have also found the exuviae. At 

 De Grassi Point the nymphs inhabit the most exposed part of the shore, where the clay 

 banks are about 2-5 feet high and are strewn thickly along the water's edge with boul- 

 ders of various sizes, which are pushed up in the spring by the ice. The water is clear 

 and practically free from vegetation, except microscopic forms, and is subject to con- 

 siderable wave action. The lake is about 2 miles broad at this point, where it forms 

 part of Cookes Bay, the main body of the lake lying farther to the north. 



The nymphs climb up the clay banks, crawling sometimes 20 feet or mox'e from the 

 water's edge, and then climb a tree, sometimes to a height of 7 or 8 feet, before trans- 

 forming. I have never been at De Grassi Point during the season of transformation, 

 and have never seen the imagoes in the oak grove, but always in the glades and along 

 the roads back in the woods, half a mile or so from the spot where the exuviae are 



