NO. 1 8 SENSE ORGANS OF COLEOPTERA — McINDOO 3 1 



(b) search for attractants and repellents, using feeding method 



A search for attractants and repellents was begun in 1928, but dur- 

 ing that year no important results were obtained. The following re- 

 marks, however, may be of some interest. A liquid, highly scented 

 with skatol, when sprayed on bean foliage in the laboratory did not 

 delay the eating of the leaves. A piece of cotton, scented with oil of 

 peppermint, was put among some bean leaves. The leaves were 

 eaten as usual. Four odorous powders were prepared with the aid 

 of heat by using (i) nicotine sulphate and lead arsenate; (2) nicotine 

 sulphate and lime; (3) tar and lead arsenate; and (4) tar and lime. 

 When these powders were mixed with soap solution and sprayed on 

 bean foliage in the laboratory the sprayed leaves were eaten almost 

 as readily as were the untreated leaves nearby. 



A wire-screen cage, 4 feet long, 3 feet wide, and 3 feet tall, con- 

 taining hundreds of adult beetles, was put in the insectary. A pan 

 containing bran bait was suspended in each corner. The first bait 

 was flavored with black-strap molasses ; the second, with amyl acetate ; 

 the third, with vanillin ; and the fourth contained only bran and water. 

 The second and third baits each attracted only a few beetles ; the 

 fourth, many ; while the first, more than twice as m.any as the fourth. 

 It thus seems that the molasses bait was slightly attractive. 



The preceding test was repeated by putting a pan containing black- 

 strap molasses and water in each corner, an aromatic being put in 

 each of three pans. The pans containing coumarin and vanillin at- 

 tracted practically the same number of beetles; the pan containing 

 amyl acetate, several more; and the pan containing only molasses and 

 water, a few more, but the attraction was not significant. 



The foregoing test was repeated by putting three pans in the cage. 

 One contained the juice from bean leaves; the second, the remaining 

 pulp of the leaves and diluted table molasses; and the third, diluted 

 table molasses. The first and third attracted beetles in equal number, 

 while the second attracted three times as many, not a sufficient number 

 to appear significant. 



A pan containing fermenting table molasses was next put in the 

 center of the cage. For five days the beetles in it were counted, but 

 no striking attraction was noticed at any time. 



Not yet having found any substance which seemed promising as 

 an attractant, the writer in 1929 decided to test a large number of 

 materials. After spending much time, 104 aromatic chemicals, 3 

 brands of molasses, 2 varieties of canesugar, and i highly scented 

 honey were tested. The method consisted of testing 8 substances at 

 one time in a small wire-screen cage. This method was found to be 

 3 



