G. S. Graiiam-Smith 
443 
boxes 1 , one (Tin I) kept in a shady, sheltered place, and the other (Tin 
II) in an open, sunny spot. In the latter the variations in temperature 
were much greater than in the former. On April 11, 1915, the pupae 
were collected from the “ tins ” and placed together with earth in wooden 
boxes provided with openings in the hds above which balloon traps 
were fitted. The two boxes were placed in the tins from which the 
pupae were taken, and the flies which emerged and found their way 
into the traps were counted daily. 
From Box No. I, 987 blow-flies ( C. erythrocephala), 489 males and 
498 females, emerged between April 23 and May 11. Up to April 29 
the males predominated, 107 males and 38 females emerging during 
that period. Later 382 males and 460 females emerged. Between 
April 22 and 30, 58 specimens of F. scalaris*, 28 males and 30 females, 
also emerged, most of the males preceding the females. At a slightly 
later period, between May 10 and 20, 10 specimens, 5 males and 5 
females, of H. dentipes emerged. Also between April 23 and May 15, 
12 specimens of Tephrochlamys cdnescens appeared. From Box II only 
8 males and 8 females of C. erythrocephala emerged between April 23 
and May 2. Here again the males appeared before the females, 7 out 
of the 8 females emerging after all the males had appeared. The rest 
of the pupae were parasitised by braconids and chalcids (p. 523). 
Food remains infested with fly larvae were placed in a third box 
in the autumn of 1914. Various species of flies emerged between 
April 23 and June 16—39 blow-flies ( C. erythrocephala), 19 males and 
20 females, appeared between April 23 and May 6, a few specimens of 
S. carnaria between May 6 and 10, 16 H. dentipes about May 20, 
19 males and 16 females of M. stabulans, and 4 males and 6 females of 
M. pabulorum between June 5 and 16, and in the early part of May 
several small Anthomyids, and numerous small flies, mostly T. canescens. 
The method just quoted was adopted in order to confine the pupae 
and the flies which emerged from them as much as possible, and so 
facilitate the recording of the results. Thinking that the conditions 
might be too favourable, since the pupae were protected from wet, 
other experiments was carried out under conditions which cannot 
differ materially from those which often prevail in nature. A small 
area of bare ground 3 x 6 ft. was enclosed by boards sunk into the 
earth and a cage of netting, ^ inch in mesh, 6 feet high super¬ 
imposed. Dead rabbits were placed on the ground and partly covered 
with leaves, and blow-flies ( C. erythrocephala ) were introduced into 
1 The construction of these boxes is described on 475. 
Parasit ol ogy vii i 
29 
