NO. 16 SENSE ORGANS OF COLEOPTERA — McINDOO 3 



In order to obtain comparative results which could be treated statis- 

 tically, new technique and apparatus were devised, and the more im- 

 jKjrtant experiments were repeated over and over under controlled 

 conditions. 



A. Tropisms 



The tropisms of Coleoptera will be discussed first and then the 

 sense receptors. 



I. PHOTOTAXIS, GEOTAXIS, AND THIGMOTAXIS 



I. REVIEW OF LITERATURE 



Information concerning the phototaxis, geotaxis. and thigmotaxis 

 of beetles is limited. Publications pertaining to light traps are numer- 

 ous, but papers concerning the geotaxis, thigmotaxis, and other phases 

 of phototaxis are scarce. In regard to the reactions of beetles to wave 

 length and intensity of light, the field is practically unexplored. 



(a) general remarks 



Loeb (T,y, p. 20) remarked that an imago animal may respond to 

 light in one way, its larva in a difi'erent way. For example, an adult 

 June beetle moves toward light and is called photopositive, whereas 

 its larva moves away from light and is thus photonegative. He further 

 said (p. 70-73) that mealworms (larvae of Tenchrio luolitor) are 

 photonegative and behave under red glass as they do in the dark ; 

 but under blue glass, just as they do in the light. They adhere closely 

 to objects, being positively stereotropic or thigmopositive. They flee 

 from moisture and seek dry spots. He believed that yx^sitive thig- 

 motaxis (stereotropism) and negative phototaxis determine the habits 

 of these insects, which live in flour, protected from the light. The be- 

 havior of cockchafers (Mclolontlia vulgaris) under red and blue 

 glass is similar to that of mealworms. Loeb believed that negative 

 phototaxis may cooperate, but that thigmotaxis is doubtless the chief 

 factor concerned in causing the larvae of cockchafers to burrow in 

 the ground. The same writer (p. 85-86) put coccinellid beetles in a 

 wooden box which was then placed in a dark closet. After repeated 

 tests these lady-beetles were always found at the top of the box, 

 proving that they were geonegative. 



Weiss (94) placed three si)ecies of lady-beetles at the base of a 15- 

 foot pole, which they soon climbed. He believes that this behavior 

 demonstrates negative ireotaxis. 



