PKOCEEDINGS OF THE THIRD ENTOMOLOGICAL MEETING 541 



" As regards attempts at artificial control of the pest in the field 

 you may perhaps be interested in an experiment I made with Ught 

 traps in 1916. 



" At Ghezireh (an island in the Nile opposite Cairo) on part of our 

 grounds which are some distance from the nearest cotton, I had sown 

 three plots of cotton each being | feddan (acre) in area. The plots 

 were separated from each other but only by quite a small distance. 

 On one plot I had 12 light traps, on another 6, and the third plot was 

 kept as a sort of control, no traps being employed on it. 



" The traps — small paraffin lamps in glass lanterns standing in trays 

 containing water with a film of paraffin on the surface, the whole 

 supported on a wooden stand about level with the tops of the cotton 

 plants, each lamp being visible from any part of the plot — were started 

 on 20th June and were run continuously until 28th September on the 

 12-lamp plot, and to 21st November on the 6-lamp plot. Heavy 

 flooding by infiltration from a high Nile caused operations to be 

 suspended so early on the 12-lamp plot. The 6-lamp plot was finally 

 flooded too but not quite so badly and we were able to get to the traps 

 by building raised causeways. Here operations were continued until 

 no more moths were caught. The flooding had, I think, a decidedy 

 adverse effect on Gelechia and so rather interfered with our experiment. 

 The control plot was also flooded — it was the first to suffer. 



" During the whole period we caught a total of roughly 16,000 

 Gelechia gossypiella. Of these we examined some 13,000 for sex, finding 

 9,000 females and 5,000 males. These figures are given under reserve 

 as I have not yet worked up in detail all the data available.* 



" Although the females greatly outnumber the males there were 

 periods when the reverse was the case. The question of the fluctua- 

 tion in the proportion of the sexes of moths captured in the traps is 

 an interesting one and needs investigating. I have no explanation of 

 it sufficiently definite to offer at present. 



" Examination of the ovaries of the female Gelechia moths showed 

 that a very large number of them contained large numbers of eggs and 

 -quite a number appeared to me to have been captured before oviposi- 

 tion had commenced. 



* In a later communication Mr. Willcocks gives the following figures : — 



Females 10,141 



Males 5,959 



Not examined .... 2,853 



Total . 18,952 



