A. Bacot and L. Linzell 391 
six lots being used, again with two eggs as control for each lot. The results 
in both cases were similar and the table below shows the net result. 
Control 
85°-100° F. 
100° 
No. of batches 
11 
11 
Eggs hatched on 
day 10 
— 
17 
99 
99 
17 ... 
3 
5 
99 
99 
18 ... 
10 
— 
99 
99 
19 ... 
11 
— 
99 
99 
20 ... 
8 
— 
99 
99 
21 
5 
— 
99 
99 
22 ... 
7 
— 
99 
99 
23 ... 
— 
— 
99 
99 
24 ... 
3 
— 
99 
99 
25 ... 
1 
— 
99 
99 
26 ... 
7 
— 
99 
99 
27 ... 
2 
— 
99 
99 
28 ... 
1 
— 
99 
99 
29 ... 
3 
— 
99 
99 
30 ... 
— 
— 
99 
99 
31 ... 
— 
— 
99 
99 
32 ... 
2 
—■ 
99 
99 
33 ... 
3 
— 
99 
99 
34 ... 
1 
— 
Failed to hatch (2 months) ... 
21 
— 
Total .. 
• • • • 
94 
22 
( e ) Incubation on the Horse. A final test was made with two batches of 
five and four eggs respectively, actually laid and remaining in a horse’s coat. 
These were obtained in July, 1918, in one of the felt-ring cages mentioned 
under Collection of Eggs. 
No. of batches 2 
Eggs hatched on day 17 3 
„ „ “18 3 
„ „ 25 1 
Eggs lost ... ... 2 
Total number of eggs ... 9 
CONCLUSIONS. 
1. Our experiments show that the eggs of H. asini may take as long as 
a month or more to hatch. Therefore animals infected with II. asini must be 
kept under observation, and the last dressing given not less than 34 days 
after the time the treatment started. 
It has not been possible to determine the minimum time required for a 
horse-louse to develop from the egg to the fertile female, but from analogy 
it will probably be about a fortnight, it having been found that in insects of 
this class the. incubation and maturation periods are approximately equal. 
