Vol. xxvi] 



ENTOMOLOGICAL NEWS 



13 



The damsel flies used were Enaiiagma and Ischnwra, indi- 

 viduals of equal size being selected. Six were placed in each 

 cage with some enemy, such as Anax or a Dytiscid larva. The 

 six enemies in the several cages were of nearly equal size. 

 At the end of 56 hours the weeds w^re examined in a white 

 porcelain tray. The results of the series are given in the fol- 

 lowing table. 



Bspcf* 



B 

 C 



% 



C 



% 



c 



Thb Emcmtcv or Shsltbb 

 NvMrasttaom 



BliilUr Phwl 



I Aaas l«al«». 



1 •• 





MrttopbrUaa 



I OytlidlikuVJ 



HonMd 4m* . . 

 I Amis fmtm. . 



I ^^„ 



IHOfMQ Qttn • •] 



MhMnlMwiB 

 Oi«*Na 



I t • 4 • 



V ; ^'» 



It 



1^1 



T 



a; 



■ 

 ki 



s 



I 



s 



>|a(i)l«i) 





^" 



(1)1 



•hoM I yt. aM. 

 AMxhi<aC»l4to4. 



The same method of placing the shelter was followed 

 throughout the series. In the second set of experiments 

 Myrl ' " m was used because its needle-like leaves oflTered 

 a diti ind of dtelter from that of Elodea. The arrange- 



ment was as follows: 



Cage 2, containing 3 bars with 3 plants each, disphced 80 

 cc. water. 



Cage 3, containing 4 bars with 4 plants eadi, displaced 170 

 cc. water. 



Cage 4, containing 7 bars with 7 plants each, displaced 375 

 cc. water. 



Cage 5, packed, displaced 845 cc. water. 



For the third set of experiments, Potamogeton crispus, a 

 fairly large plant, with long, broad leaves, was chosen. 



