156 THE SENSE ORGANS AND BEFLEX BEHAVIOUR 



prompted by such metaphysical ideas, there is a need for a more 

 scientific analysis of insect behaviour, and for the discovery of any 

 quantitative laws that may govern their reactions. In this con- 

 nection it may be pointed out that insects have been shown to be 

 attracted to chemical compounds that are neither associated 

 components of their food, nor occur in the natural environment 

 of the species concerned. 



The fact that insects are powerfully attracted to certain kinds 

 of food materials is a matter of common observation. It has only 

 been during about the last twenty years, however, that economic 

 entomologists have made systematic efforts to take advantage of 

 this phase of behaviour in devising methods of repression. The 

 practice of exposing traps or baits, containing molasses as their 

 chief chemical constituent, has now become a widespread and 

 familiar measure. Little is definitely known with respect to the 

 specific attractive ingredients of this mixture of substances, but 

 all observations show that its chemotropic properties are greatly 

 enhanced in the presence of fermentation. It is especially 

 attractive to many species of moths, particularly to those of the 

 family Noctuidse, while numerous species of Diptera, whose larvae 

 inhabit decaying organic matter, likewise respond. Molasses 

 baits were at one time a common method of controlling grape- 

 vine moths in Europe, but in recent years it has fallen into 

 disrepute. At the present time much attention is being given 

 to chemotropic measures in the control of the Codling Moth 

 (Cydia pomonella) and the Oriental Peach Moth (C (Grapholitha) 

 molesta). Yothers (1927) has described the results of three years' 

 experiments in trapping the first-mentioned insect. A number of 

 substances were tested, but fermented molasses proved the most 

 efficient, and captured many thousands of moths per acre during a 

 season. About 55 to 60 per cent, of the insects captured were 

 females, and among them about 95 per cent, were gravid, having 

 laid none or very few of their eggs before capture. He stresses 

 the use of such baited traps for determining the beginning and 

 end of the season of flight of the insect, the beginning and end 

 of each generation, and the period of maximum abundance. 

 Information thus gained may be used to advantage in arranging 



