BULLETIN 14, U. S. DEPARTMENT OF AGRICULTURE. 
Table III. — Migratory habit of housefly larvae; experiment No. 3. 
Date. 
Larvae 
collected 
from pan. 
Flies 
caught 
in traps. 
Date. 
Larvae 
collected 
from pan. 
Flies 
caught 
in traps. 
1913. 
Nov. 14 
15 
16 
17 
18 
19 
20 
21 
22 
23 
24 
25 
26 
162 
656 
1,950 
2,650 
1,240 
40 
0) 
12 




1913. 
Nov. 27 
28 
29 
Dec. 1 
2 
3 
4 
5 
6 
3 
2 
2 
2 
8 
5 
6 
15 
10 
3 
7 




4 
2 
6,710 
69 
i Collected on following date. 
Out of a possible total of 6,779 there were destroyed 6,710 larvas, 
that is to say, about 99 per cent were destroyed before they reached 
the pupal stage. 
The percentages obtained in these experiments clearly demonstrate 
the habitual nature of the migration. They also demonstrate the 
efficiency of the maggot trap which is designed to take advantage of 
this mode of action. The question immediately arises whether the 
trap which appears so successful in an experimental way on a small 
scale can be adapted to the handling of manure in a practical way and 
on a large scale. Every consideration points to the probability that it 
can and that it will afford "an additional weapon ol^reat value." 
However, the final verdict as to the value of the maggot trap must 
wait upon the solution of certain practical problems. To point out 
some of these here is to suggest lines for further investigation. 
(1) In the first place, there must be determined what form, size, 
and construction of trap will give the best results. The answer to 
this will depend largely on the particular conditions obtaining at any 
given stable, such as the amount of manure produced daily, the 
arrangements for drainage, etc. It will also depend on the answer to 
the following problems : 
(2) How deeply may manure be heaped in a trap without inter- 
fering with the migration ? It will probably be found that the depth 
will make little difference, provided that the manure is kept moist, 
and provided that avenues of escape are afforded at the sides as well 
as at the bottom. The importance of providing a way of escape at the 
sides was not taken into consideration by Levy and Tuck in their 
preliminary experiments. 
(3) How long must manure be kept in a maggot trap before it is 
entirely free from larvse ? This is a very important question from a 
practical standpoint, and one will find scant suggestion as to the 
answer in the literature on the life history and habits. The housefly 
