BEHAVIOR AGREEMENT AMONG ANIMALS. 299 



determined by current and light. Controls show little or no 

 activity. 



Hydro psyche (Fig. 4) [2-10 min.]. Strongly thigmotactic ; the 

 majority often did not leave the screen, and in some experiments 

 they showed little positive orientation so several experiments 

 were performed and an experiment which represented our general 

 experience with them was selected for tabulation. Their tubes 

 nearly always face the current in the rapids of streams (Wesen- 

 berg-Lund 'n) and in experimental conditions where they are 

 allowed to spin. They appear to have a greater efficiency in 

 the current than any other of the species studied. When 

 poured into a 60 cm. per sec. current, one out of three individuals 

 succeeded in obtaining silk attachment and moved upstream 

 I cm. per min. on a comparatively smooth wooden bottom. 

 With the tubes once constructed they are secure against anything 

 but floating objects. 



Argia (Fig. 5) [2-5 min.]. Awkward in current. Orients well 

 in very weak current due to large gill plates which act like a 

 weather vane. 



Perla (Fig. 6.) and Heptageninae (Fig. 7) [530 sec.]. Both 

 good runners; both crouch close to the bottom, especially the 

 latter. 



Psephenus (Fig. 8) [3-15 min.]. Slow to orient but very effi- 

 cient in current. 



Pool Community. 



Notropis (Fig. 9) [immediately]. Swims constantly. 



Hybopsis (Fig. 10) [immediately]. Swims and rests on bottom 

 with head up stream. 



Ambloplites (Fig. n) [immediately]. Swims constantly; in 

 strong current the fishes are thrown sidewise against the lower 

 screen and cannot dislodge themselves. 



Calopteryx (Fig. 12). Variable time to first reading began 

 when one left lower screen. 



Campeloma (Fig. 13) [30 min.]. Good efficiency against current 

 on account of large foot. Inactive in very strong current. 



Macromia (Fig. 14). Apparently indefinite. Sometimes mov- 

 ing up or down in the trough ; frequently resting for long periods 



ith the posterior end up stream. 



