NATURAL HISTORY AND GENERAL BEHAVIOR OF THE 
EPHEMERIDAE NYMPHS HEPTAGENIA 
INTERPUNCTATA (SAY). 
By J. E. WopSEDALEK. 
There is a comparatively small amount of literature on the 
behavior of the Ephemeride. Probably the best general 
account is that given in Miall’s ‘Natural History of Aquatic 
Insects.’’ This treatise contains greatly abridged and repro- 
duced in English, the useful account of the life history of the 
Ephemera found in Swammerdam’s “Biblia Nature,’’ and the 
very entertaining description of Reamur, but the behavior of 
these insects has been a subject of practically no experimental 
investigations. The species upon which the present study is 
based is Heptagenia interpunctata (Say), which is described 
in Needham’s work on ‘‘ May-Flies and Midges of New York.’’ 
HABITAT AND GENERAL HABITS. 
Especially in the fall of the year these nymphs are found in 
ample abundance clinging to the under sides of rocks on the 
shores of Lake Mendota. Although they may be found under 
almost any rock, they are most numerous on greenish brown 
stones corresponding to the coloration of the nymphs, and pre- 
senting a rough surface well covered with small aquatic plants. 
This choice of habitat is probably determined, to a great extent 
at least, by their negative phototaxis and strong positive 
thigmotaxis, since I have never seen the nymphs on the upper 
or the lateral faces of stones. 
In a previous paper* the reactions to light and their control 
by chemicals in H. interpunctata have been discussed in con- 
siderable detail. It was found that when the nymphs are 
placed in a long glass dish of water near a window they immedi- 
ately swim away from the light. The same negative reaction 
takes place when the dish is taken into a dark room and a light 
is introduced near one end. It was also found that this strong 
negative phototaxis can be reversed by means of various 
chemical solutions. 
*Wodsedalek, J. E. Phototactic Reactions and Their Reversal in the May-Fly 
Nymphs Heptagenia Interpunctata (Say). Biological Bulletin Volume 21, 
Pages 265-272, 1911. 
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