2 ENTOMOLOGICAL NEWS [Jan., ' 1 5 



there. The distribution of the nymphs in the stream bed and 

 in the submerged vegetation has been studied, and is reported 

 on in the following pages. The epiphytes and epizoa attached 

 to the skin of the nymphs have been studied and are here 

 Hsted for the first time. A whole population of epiphytes 

 consisting of diatoms and other algae, and of epizoa, num- 

 bering some Protozoa and other microscopic forms, live habit- 

 ually upon the backs of members of all families. Special 

 attention has been given to food, which consists of almost any 

 animal small enough for the nymph to hold. It varies, there- 

 fore, much in character and abundance according to the sea- 

 son. Chironomids and the young Odonate nymphs are always 

 at hand; mayfly nymphs most of the time, and other forms 

 only at certain seasons. Finally, some experiments to deter- 

 mine the protective value of water weeds as shelter for the 

 nymphs are here recorded. 



This study was suggested by Prof. James G. Needham, to 

 whom it gives me sincere pleasure to express my gratitude for 

 his kindly advice and criticism. 



The Aquatic Situation. 



Along the southern border of the Cornell University Cam- 

 pus, Cascadilla Creek flows swiftly over a bed of rocks and 

 gravel, falls two or three feet over shelving rocks and then 

 divides. One branch soon widens out into a broad sluggish 

 basin and the narrow part of the stream dries up except during 

 the spring and fall overflows. In the summer there is no 

 noticeable current and the basin is then known as Cascadilla 

 Pond. The other branch flows rapidly over a bed of pebbles 

 and gravel for a short distance and then quiets down before 

 joining with the first branch to form Dwyer's Pond. 



The grassy meadow shut in by steep slopes on the north 

 and west and traversed by these two branches of the creek, 

 whose banks are partially shaded by trees, is an ideal home 

 for the imagos ; while the waters, swift or quiet, with beds of 

 gravel and mud supply the diversity required by the nymphs. 

 (Plate I, Fig. i.) 



