REACTIONS TO CHEMICAL STIMULI 161 



Anthomyidse responded in large numbers. Roubaud and Veillon 

 (1922) experimented with the attraction of simple products of 

 fermentation with regard to nineteen species of flies. They 

 found that sugars, non-fermented sugar products, alcohols and 

 ammonia produced little or no positive reactions on the part of 

 the insects. Among the various compounds resulting from 

 organic fermentation the most attractive were ammonium 

 sulphohydrate, ammonium valerianate, valerianic acid and 

 trimethylamine. Peterson (1924) found that fermenting yeasts 

 were highly attractive to the flies Hylemyia cilicrura and H. 

 antiqua, probably, as he remarks, on account of the alcohols and 

 ethereal odours produced. Various alcohols, added to honey and 

 water, proved powerfully attractive, especially alyl alcohol and 

 isopropyl alcohol. A number of other paj^ers of a kindred nature 

 to the foregoing have appeared, and the results obtained indicate 

 the complexity of the subject. By no means all the substances 

 tested induce feeding reflexes, and in many cases the significance 

 of the responses is unknown — they appear to be non-purposeful 

 in that they are unconnected with any vital functions. There 

 are other instances where certain compounds have been shown to 

 exercise an influence in connection with oviposition. Both 

 Roubaud and Veillon, and Richardson, have pointed out that the 

 female house-fly, for example, is attracted to the manure heap 

 for purposes of egg-laying, feeding mainly taking place elsewhere. 

 The part performed by chemical stimuli in inducing oviposition 

 has been discussed by Richardson (1925), who gives reasons for 

 concluding that, in the house-fly, ammonia is one of the volatile 

 constituents of the manure heap that is important in this respect. 

 Crumb (1924) has published the results of experiments showing 

 that the addition of hydrogen sulphide, old yeast infusion, methane 

 or stale urine to water, in each case, t^nds to induce oviposition in 

 the mosquito Culexpipiens. Ordinary tap water, used as a control, 

 exercised no influence. 



There are, again, other examples where specific compounds have 

 proved attractive to the male sex only. This was well shown in 

 the important experiments of Howlett (1912), dealing with the 

 reactions of certain Indian fruit -flies. He found that citronella oil 



R.A. ENTOMOLOGY. 6 



