NO. l8 



SENSE ORGANS OF COLEOPTERA — McINDOO 



33 



indicated by the fourth row. According to this arrangement of food, 

 no two rows in the same cage were exactly ahke ; hkewise, no two rows 

 of all i6 rows were identical, although the distribution of food was 

 not so complete. These four series of tests were conducted during 

 the forenoon, and then usually repeated in the afternoon. Each 



D E 



Fig. 5. — Diagrams of wire-screen cage (A) and arrangement of substances (B, 

 C, D, and E) to be tested by bean beetles. See text, p. 32, for further 

 explanation. 



individual substance used was therefore tested 16 times in the fore- 

 noon and usually 16 times in the afternoon. 



It was difficult to decide whether tests of this kind should be con- 

 ducted in the dark-room or in the well-lighted laboratory. After try- 

 ing the dark-room it was observed that the bean beetles did not eat 

 freely either in artificial light or in total darkness. So it was de- 

 cided to place the cages on a table by a south window, but not in the 



