198 JOURNAL, BOMBAY NATURAL RIST, SOCLETY, Vol. XXIV. 



After staying about 16 to 24 hours the large majority cleared away to 

 the north, leaving a number of stragglers here and there. 



Locusts have never been known to visit this country before, and I report 

 the occurrence since it seems extraordinary that they should visit a district 

 of heavy rainfall such as this is. 



W. LANCELOT TRAVERS. 



Baradighi S. E., Ja-Lpaiguei, 

 lO^A July 1915. 



No. XVI.— " CHEMOTROPISM, INFLUENCE OF KUSUM 



OIL ON INSECTS." 



Everyone is familiar with the smell that some bugs emit. This odour is 

 due to the secretion of a fluid from special glands located in different 

 places in the body of insects which are known by various names such as 

 Oderiferous glands, Stink glands. Scent glands. This fluid may be disagree- 

 able or sweet in its smell, may serve as a means of defence against enemies, 

 may act as an attraction for opposite sex, and fulfil many other purposes. 



In the case of young nymphs in Rhynchota, these glands are situated on 

 the abdomen, while in the case of adults they are located on either side of 

 the metathorax and are covered over by the wings. 



During winter of the year 1913 Mr. Puran Singh, Chemical Adviser to the 

 Forest Research Institute, while dealing with kusum {ScMeichera trijuga) 

 oil, noticed a species of insect in and near his laboratory. He, thinking 

 that it might be of some interest to me, kindly gave me this information, 

 adding that the oil attracted these insects. After a careful search it was 

 ascertained that the insects Avere not breeding in the laboratory but 

 were attracted there by something, probably by the smell of the kusum oil, 

 and it was considered interesting to study the peculiar fascination (if any) 

 the bug had for the oil. 



It was first thought that there was some similarity in the smell of this oil 

 to the smell emitted by the fluid from the stink glands of the female bugs, 

 and it was for this reason that the male bugs only were attracted to the oil 

 in numbers. On subsequent care'ful examination of the insects present 

 near the oil, and conducting the experiment at different places in Dehra 

 Dun, it was evidenced that it was not one particular sex only that came 

 near the oil, but both the sexes in all their stages of development were seen 

 on and near the oil. So it goes clearly to show that it is not the male only 

 that is carried to the oil by its similarity in smell to the fluid from the stink 

 glands of the female, but that the oil has a chemotropic influence on both 

 sexes of the bug. That the bug is led blindly to follow the line of diffusion 

 of the smell of the oil is beyond doubt, and I believe that a psychological 

 reaction is produced on the insect by the oil, which compels it to go to the 

 oil, in much the same way as a moth follows a ray of light to its source. 



One can within a few hours catch a large number of males, females, and 

 nymphs, even very small ones, by sprinkling a few drops of the oil on a sheet 

 of paper, stone or any other suitable object. It has been observed that the 

 nearer the oil is to the insects the larger is the catch. The above has a 

 bearing on the rate of ''attraction," which depends also on the direction in 

 which the wind is blowing. I have within a course of seven days caught 

 about 3,000 of these bugs (males, females and nymphs) from different locali- 

 ties in Dehra Dun of which I give below a list with dates : — 



