NO. l8 SENSE ORGANS OF COLEOPTERA — McINDOO I5 



cussed the subject of tropisms from a broad point of view, and has 

 not yet accepted any definition nor does he know exactly what a 

 tropic response inckides, but he beHeves that it includes more than 

 orienting in a certain direction. 



In conclusion, bean beetles and their larvae are usually found on 

 the upper portions of their host plants, because they are photopositive 

 and geonegative ; but since direct sunshine in warm weather is harm- 

 ful to them, they are usually found on the lower surface of the leaves. 



II. CHEMOTAXIS 



I. REVIEW OF LITERATURE 



Most of the information regarding chemotaxis found in the widely 

 scattered literature pertains to the subject of baits. Scores of refer- 

 ences have been consulted, but only the more important ones will be 

 cited. 



(a) baits for wireworms and tenkbrionids 



It is not known when the practice of using baits for beetles was 

 first begun, although this is an old control method. The Japanese 

 growers, according to Treherne (85), were probably the first ones 

 to use baits for catching wireworms, the larvae of elaterid beetles. 

 After roasting dry rice shorts or rice bran, the Japanese then mois- 

 tened the roasted material with water and made it into small balls, 

 which had a strong odor said to be attractive to wireworms. The 

 Japanese claimed that a single ball would catch 100 or more wire- 

 worms, but when this method was tested by Treherne a single bait 

 buried in heavily infested soil never yielded more than 90 larvae. 



Treherne (86) also tells about the old-fashioned way of attracting 

 wireworms, which is still recommended as one of the few control 

 measures. Pieces of cut potatoes, to which white wires have been 

 attached, are buried in the infested soil. Upon visiting the infested 

 area the potatoes are pulled from the ground by means of the wires, 

 the wireworms are removed and destroyed, and then the potatoes are 

 buried again. In Canada attractive baits, consisting of potatoes, balls 

 of dough, shorts, meal, or rice bran, are set in the soil. The addition 

 of molasses or other attrahent (" attractant ") in these bran baits 

 does not improve their attractiveness, nor has the inclusion of ar- 

 senicals been of any practical value. 



Weldon (95) reports that small pieces of ixjtatoes were planted 

 between rows of beans in California. This bean crop was saved, while 

 30 acres of beans nearby, not thus protected, were entirely destroyed. 



