NO. l8 SENSE ORGANS OF COLEOPTERA — McINDOO I9 



The first authentic report on this subject is by Smith (76), who 

 states that in chemotactic studies it has been found that Japanese 

 Ijeetles are strongly attracted by geraniol, and nearly 50,000 beetles 

 in 1924 were collected from baits containing this substance. Bait 

 mixtures, containing bran, molasses, and geraniol retain the odor for 

 a long time if protected from the rain. Eugenol, citral, and citronellol 

 as attractants, and tar oil as a repellent, appear to have some value. 



Richmond (66) gives a detailed reix)rt on this subject and tells 

 about the earliest experiments conducted. Since the beetles were 

 known to have favored food plants and were strongly attracted to 

 ripening fruit, various chemicals were tested in 1922 to ascertain if 

 the fruit odors might be imitated. To determine whether beetles could 

 he attracted to the sources of odors, a number of essential oils were 

 sprayed on foliage. The results indicated that the oils of sassafras, 

 hemlock, mustard, and lemon, and iso-amyl valerate were somewhat 

 attractive. More detailed experiments were conducted in 1923 and a 

 large number of compounds were studied. Bran-bait mixtures, put in 

 cans which hung in trees, were used. Among the oils, sassafras and 

 clove were easily the leaders, while ethyl alcohol, geraniol, and eugenol 

 proved to be the most important constituents. In 1924 greater detailed 

 studies were undertaken. The adult beetle was found exceedingly 

 susceptible to the influence of color, odor, temperature, humidity, and 

 light. The six leading chemicals tested are geraniol, eugenol, cit- 

 ronellal, citral, citronellol, and diphenyl ether. Geraniol proved to be 

 far superior to the other five. In other exi)eriments emulsions were 

 tested. When cloths (i foot square) were dipped in a 10 per cent 

 emulsion of geraniol and suspended in orchards (pi. i. A), beetles 

 were drawn as if by a magnet and 13,000 beetles were collected on 

 12 cloths over a period of 5 successive days. In 1925 and 1926 this 

 project was much expanded so that it included the testing of various 

 types of bait cans and bait traps. The best type of trap devised 

 was cylindrical in shape. A single one of these caught over 13,000 

 beetles in 8 hours. Richmond's summary follows : 



Geraniol is clearly the primary attrahent of the Japanese beetle but its com- 

 bination with eugenol materially lowers the cost and increases its effectiveness. 

 During the summer of 1924 over 65,000 beetles were actually collected from the 

 bait can experiments. Nearly 50,000 of these beetles were present on geraniol 

 baits alone. The results of experimentation in 1925 and 1926 were in keeping 

 with these remarks, but, inasmuch as more extensive tests were conducted, the 

 number of beetles collected was proportionately greater. The activities of the 

 adult varied with temperature, humidity and vapor pressure. Females are 

 attracted approximately one-third more frequently than males when geraniol 

 and most other chemicals are employed. Molasses has only a slight attractive 



