A. D. Imms and M. a. Husatn 27:3 



observations dealing with the reactions of certain Indian fruit flies. 

 He found that citronella oil exercises a remarkable attraction for the 

 males of Dacus diversus and D. zonatus, and suggested that possibly this 

 reagent is allied to a secretion emitted by the females, and that the 

 phenomenon of the only being attracted is to be regarded as a repro- 

 duction, by artificial means, of a sexual attraction similar in kind to 

 that which operates in most cases of "assembling." In a later paper 

 (1915), Howlett conducted a further series of experiments, confirming 

 his previous results that certain odours are remarkably attractive to 

 male flies of the genus Dacus and, that by the employment of attractive 

 substances, the movements of the flies can to a great extent be controlled 

 in any given direction. Three of the common species (Z). diversus, 

 ferrugineus and zonatus) normally breed respectively in (1) anthers of 

 Cucurbitaceae, (2) fruits of Solanaceae and mango, and (3) peach, guava, 

 mango and other fruits. D. diversus (1) is most strongly attracted by 

 iso-eugenol, zonatus by methyl-eugenol, and ferrugineus (2) by both 

 iso- and methyl-eugenol. The odours of these substances have not yet 

 been identified with those of the plants which constitute the normal 

 breeding-places, but male flies have been found attracted to mango, 

 Papaya, a Cycad and Colocasia, plants with a very characteristic smell 

 similar to that of eugenol-derivatives. Females have never been seen 

 to frequent these plants or to breed in them, but more extended observa- 

 tion on this point is needed. Three explanations suggest themselves, 

 (a) That the smell is a direct sexual guiding smell, emitted by the female 

 as previously suggested, but the young crushed females do not attract 

 males. (6) The smell is not emitted by the female, but may be termed an 

 "indirect" sexual guide to the plants where the females are accustomed 

 to congregate for breeding purposes. Under these circumstances it is 

 difficult to see why females should not be attracted by the odoriferous 

 chemicals, (c) The odour is a food smell; if this be so it can only be 

 attractive to males. It is evident that further critical research is greatly 

 needed eliminating, at any rate for the time being, the metaphysical 

 conception of purpose. In a third paper Howlett (1914) noted the marked 

 response of Thrips to the stimulus of the odours of benzaldehyde, cin- 

 namylaldehyde and anisaldehyde. In his earlier paper (1912), Howlett 

 conducted a further series of experiments with regard to the influence 

 of reagents upon oviposition and it appears not unlikely that the odours 

 of chemical substances provide the required stimulus. Thus, he found 

 Sarcophaga to be very strongly attracted to a flask containing a solution 

 of skatol, a substance normally present in faeces and many larvae were 



