G. S. Graham-Smith 
501 
about, and, except when feeding, seldom remaining long in one place. 
This occurred even when the day was moderately cold. Very close, 
sultry weather had a peculiar effect. The flies became very sluggish, 
were apparently unwilling or unable to fly, and clung tenaciously to 
anything on which they settled. Such weather caused great mortality. 
Their behaviour on overcast days with brief periods of sunshine was 
most interesting to watch. When the sun came out flies, which were 
taking refuge in crevices, began to stir, and soon came out into the 
sunshine. If the day was warm they flew about, but if it was cold 
they remained close to the crevices, and when clouds obscured the sun 
often went back slowly into their sheltering places. On cold days with 
gleams of sunshine the flies were often seen sunning themselves in a 
peculiar manner. They so arranged themselves as to present their 
dorsal surfaces as much as possible to the sun, often leaning at consider¬ 
able angles in order to accomplish this, with the legs of the side nearest 
to the sun contracted and those of the opposite side more extended. 
On. sunless days the flies seldom flew, and usually remained very quiet, 
occasionally walking slowly from place to place. In very cold weather 
they remained motionless in crevices and corners for days together. 
In windy weather the flies moved about very little, but sought 
situations sheltered from the wind. 
During rain the flies usually congregated in protected situations, 
and changed the situations first chosen, if the direction of the rain 
altered. 
The behaviour of the flies in the evening depended on the tempera¬ 
ture. On warm evenings they were widely distributed near the roof 
of the cage and did not go into corners, etc., but on cold evenings they 
gathered in clusters in the corners, often close to the ground (PI. XXIII, 
fig. 28), and many sought shelter in crevices. 
As the flies often clustered in large numbers in dark corners and 
were in consequence difficult to count, white strips of wood were fixed 
in these corners to render counting easier, but after this most of the 
flies avoided these white pieces of wood, and seemed to prefer to settle, 
especially in the evening, in darker places, where they were less visible. 
This hypothesis seems to be confirmed by the fact that the under 
surfaces of dark, dead artichoke leaves, where the flies were almost 
invisible, were very favourite resting places in the evening. 
Flies depositing eggs and feeding on animal carcases often seem to 
be so occupied that they are not easily disturbed, and on cold or sunless 
days many will not move, even if touched. For oviposition they seem 
