INSTITUTE, PUSA, FOR 1917-18 119 



quitos (especially Stegomyia scutellaris) in their choice of 

 breeding-places, and the deterrent or attractive effect of 

 dilute solutions of a number of chemical substances as com- 

 pared with pure water. 



The results at present obtained indicate that — 



(1) Temperature has a definite influence, eggs being 



laid more freely in warm water. 



(2) Various chemical compounds have a deterrent 



effect when dissolved in small quantities f|-l 

 per cent.) in the water. 



(3) A few chemical substances (especially sodium 



citrate and tartrate) have an attractive effect, a 



far larger number of eggs being laid in dilute 



solutions of these substances than in pure water. 



This work is being continued, in conjunction with 



experiments on the effect of dilute solutions of chemical 



compounds on the development of mosquito larvae. 



IV. Insect Psychology in relation to Feeding and 



Oviposition. 



A good deal of work has-been done in this direction, 

 but the results are not of a kind to be profitably discussed 

 in a report of this nature. 



One immediate outcome of them was the series of 

 experiments on the egg-laying of mosquitos mentioned in 

 the preceding section, and they have had a direct bearing on 

 the work in connection with repellants. 



V. Insect Eepellants and Insecticides. 



The subject of repellants and insecticides is one to 

 which I have given much personal attention in the course 

 of the last four years, and since my return from England 

 I have continued experiments on repellants, and have 

 attempted to devise standard methods for testing repellants 

 and insecticides which will give a reliable index of their 

 actual practical value. 



Practical work in this connection, in collaboration with 

 Captain Pool, A.V.C., was undertaken at the instance of 



