18 J. E. WODSEDALKK 



point of the process projected about half an inch above the 

 surface of the water, pointing toward me. The insect at this 

 stage would readily follow a piece of food to the projection, 

 which became its regular feeding place. At the end of about 

 two months the insect spent practically all of its time, during 

 my presence, perched up near the point of the projection with 

 its head just below the surface of the water. The time and 

 clearness of the day seemed to play no important part on its 

 behavior. Even at night when the electric light was directly 

 over the table on which the insect was located, it would not 

 desert its favorite resting place. Almost invariably, when I 

 had left the room the nymph would soon retire to the under 

 side of the stone. All that w T as necessary, at this time, to bring 

 the specimen up when it had disappeared from sight was to 

 slightly jar the dish or the table on which the dish was located, 

 and the insect would quickly come up to the upper side of the 

 rock and make directly for its feeding place. Later, very fre- 

 quently as I stepped into the room I caught the insect in the 

 act of coming out from its hiding-place and halting at the end 

 of the projection ready to receive its usual reward. 



Sometimes, when I had been gone from the room all day 

 and did not feed the nymph shortly after my appearance, but 

 simply moved my hand over it, the insect would slowly crawl 

 up on the point of the rock extending out of the water. How- 

 ever, it usually exposed only its head and thorax to the air 

 and apparently exercised considerable care not to expose the 

 abdomen, which bears the tracheal gills. Although I antici- 

 pated extended experiments with this entertaining individual, 

 all was brought to a close by its metamorphosis. Nothing 

 more could be done with it in the adult stage, as the Epheme- 

 ridae never take food after they emerge, and live but a few 

 days at most. Here again, we have obvious signs of the forma- 

 tion of associations. 



Sondheim ' accidentally made some observations and later per- 

 formed some experiments with a dragon-fly larva, Aeschna 

 grandis L., and obtained practically similar results during a 

 much shorter time and with far less effort. This is probably 

 due to the fact that the natural habits of A. grandis are much 



1 Sondheim, Maria. Wahrnehmungsvermogen einer Libellenlarve. Biologisches 

 Centralblatt, Bd. 21, S. 317-319. 1901. 



