474 Observations on Habits and Parasites of Common Flies 
the house. About two-thirds of the area of the garden was occupied 
by a lawn and the rest by flower beds, etc. (Plate XXV). 
The purposes of these observations were to ascertain the numbers 
and kinds of flies attracted throughout the season to fresh human 
excrement, to the carcases of small animals, and to fruit, the results 
of placing these baits in darkness, in the shade and in the open, and the 
effects of varying weather conditions. These experiments were supple¬ 
mented by catching and examining “wild” flies and observing their 
habits. 
Daily records of the maximum and minimum readings of earth 
thermometers, at depths of two inches and of one and two feet, in the 
open and in the shade, of a thermometer placed on the grass, of a 
thermometer exposed to the sun, and of thermometers placed in the 
two galvanised iron traps (p. 475) were kept. The quantities of rain 
falling during the day and night were separately recorded and notes 
made as to the direction and strength of the wind, and the general 
weather conditions. The writer is greatly indebted to Mr R. I. Lynch 
for allowing him to make use of the daily sunshine charts obtained 
at the University Botanic Gardens, and to Messrs W. E. Pain and 
Sons for records of the mean daily velocity of the wind. 
Open traps, constructed of mosquito net, 
A very satisfactory, easily constructed and cheap form of trap, 
into which all the species attracted by the baits enter readily, is made 
in the following way. The base consists of a light, wooden framework 
18 x 18 inches. A strong galvanised iron wire runs through each 
corner and projects downwards two inches below the wooden frame¬ 
work. These projections are forced into the ground and help to fix 
the trap. Above the framework the wires are carried vertically up¬ 
wards for six inches. At this point they are bent inwards, and carried 
upwards for six inches to be inserted into the four corners of a square 
piece of wood 6x6 inches with a round hole, three inches in diameter, 
cut in the centre. 
At the level of the bend just described a wire is carried round the 
trap. This wire is fixed to the vertical portions of the four corner 
wires. On the lower wooden framework four wires are fastened parallel, 
but four inches internal, to the four sides. The intersections of these 
wires enclose an area ten inches square Mosquito net, ^ inch mesh, is 
sewn round the upper sloping portion of the wire frame and fixed by 
laths to the upper square piece of wood. Erom the encircling wire the 
