Gr. S. Graham-Smith 
499 
Chart 6. It will be noticed that the numbers gradually increased 
up to 1.30 p.m., after which there was a rapid fall to a moderate level, 
and then a gradual decline. The curve for flies on such days corresponds 
closely in form to the curve for the hourly readings of the “sun” 
thermometer. The influence of the sun temperature on the activities 
of flies could be investigated most satisfactorily with the aid of a 
thermograph placed in the neighbourhood of the traps. 
Chart 6. Showing th-e number of flies caught hourly in the various traps on 
June 12, 1915. 
Oppressive, sultry days. A remarkable and interesting effect of 
weather conditions on flies was noticed on a few occasions. September 
15 and 16 were very sultry, oppressive days, and the blow-flies in the 
outdoor cage were greatly affected. They were disinclined to fly, 
crawled about slowly, clung tenaciously to the clothes of persons 
entering the cage, and died in large numbers (p. 464). “Wild” flies 
seemed to be similarly affected. Very unusual numbers visited trap III, 
a dark receptacle baited with excrement, which was in the shade in 
the afternoon; many of those caught in the traps died, and very few 
entered the house except in the morning and evening. June 7 and 8 
and July 5 and 6 were somewhat similar days, and produced identical. 
