144 
THIRTEENTH REPORT. 
01) ON AT A COLLECTED AT DOUGLAS LAKE, MICHIGAN, IN THE 
SUMMER OF 1910.* 
ABIGAIL O’BRIEN. 
The Odonata in the following list were observed in the immediate 
vicinity of the University of Michigan Biological Station at Douglas 
Lake, Cheboygan County, Michigan, between July 9 and August 26. 
Thanks are due to Dr. A. S. Pearse, Assistant Director of the Station, 
for advice and assistance; to Mr. E. B. Williamson of Blufftou, Indiana, 
for valuable suggestions and the identification of the specimens of species 
numbers 8, 12 aud 13, and the verification of the writers identification of 
specimens of species numbers 4, 16, 17, and 18, and to Mr. E. M. Walker, 
University of Toronto, for identification of the specimens of species num- 
bers 20. 21 and 22. 
1. Enallagma carunculatum Morse. — Very common throughout the 
whole time. 
2. Enallagma cxsulans Hagen. — Several taken, two in copulation. 
3. Isclmura vertical is Sag. — Two females and one male taken August 
20 . 
4. Lestes disjunctus Selys. — First taken July 22, common till 
August 15. 
5. Lestes uneat us Kirby.— Taken several times from July 23 till 
August 20. 
6. Lestes unguiculatus Hagen. One male taken August IS. 
7. Lestes forcipatus Rainbur. — Several of both sexes taken August 
19. 
8. Xehalennia ircna Hagen. — Taken July 23 and later until 
August 20. 
9. Sympetrum assimilatum Uhler. — Male and female taken together, 
also other specimens, August 19. 
10. Sympetrum obtrusum Hagen. — Taken from July 23 to August 20. 
11. Sympetrum rubicundulum Say. — Common at several places 
around the lake from August 8 to August 15, rare after the latter date. 
12. Sympetrum costiferum Hagen. — Common from August 1 to 
15. Tarsi were black instead of yellow as given by Muttkowski (Bul- 
letin Wisconsin Natural History Society (2) 6, page 111, (1908). 
13. Sympetrum scoticum Donovan. — A few taken on August 11. 
14. Progomphus obscurus Selys. — Four adults taken about the camp. 
Nymphs were very common in the sand along the lake shore under a 
few inches of water. Efforts were made to raise them from nymphs kept 
in receptacles near the laboratory, but they were unsuccessful. The 
species apparently has not been reported from as far north as Douglas 
Lake. The nymphs were common all summer but adults were not found 
after August 11. 
* Contr but ; ons from the Zoological Laboratory of the University of Miclrgan, No. 134 (B'ologica 
Station Series, Zoological Publication No. 4. 
