80 INSECTS AFFECTING DOMESTIC ANIMALS. 
Four weeks after hatching the eggs opened with the slightest touch 
of a wet finger, and the larve adhering to the finger were very active, 
though in some cases they were inactive and apparently dead. About 
five weeks after collecting the eggs nearly all gave only inactive or 
dead larvee, though opened with ease on being touched with the finger, 
and in forty days after collecting no living larvze could be found in the 
remaining eggs, except one which had succeeded in pushing off the cap 
of the egg and partially emerging. 
In view of these results, I coneluded: 
(1) That the eggs of the horse bot fly do not hatch, except by the assistance of the 
horse’s tongue. 
(2) That hatching does not ordinarily occur within ten or twelve days and possi- 
bly longer, or if during this period, only on very continuous and active licking by 
the horse. ; 
(3) That the hatching of the larve takes place most readily during the third to 
fifth week after deposition. 
(4) That the majority of the larve lose their vitality after thirty-five to forty 
days. 
(5) That larve may retain their vitality and show great activity upon hatching — 
as late as thirty-nine days after the eggs were deposited. 
(6) That it is possible, though not normal, for eggs to hatch without moisture or 
friction. 
(7) That in view of these results, the scraping off of the eggs, or their removal or 
destruction by means of washes will be effective, even if not used oftener than once 
in two weeks during the period of egg deposition, and, probably, that a single 
removal of the eggs after the period of egg deposition has passed, will prevent the 
great majority of bots from gaining access to the stomach, or at least so large a 
proportion that little injury is likely to occur. 
Wishing to know still more definitely the period of most ready hatch- 
ing, and the effect of different washes for treatinent, I suggested to a 
veterinary student, Mr. Harry Shanks, a careful series of observations, 
which were carried through during the summer of 1894. 
From this study, which was made under my direction, and so that I 
had frequent opportunity to note progress, a number of points were 
gained, which are worth adding to the above record. Three hundred 
eggs were collected from a horse which had been previously freed from 
eggs, So that the exact date of deposition was assured. The eggs were 
tested every day. 
On the day of collection (first day) the eggs appeared immature. One 
day later eight eggs opened by picking the operculum off showed three 
larvee with slight movement, and five immovable. On the third day a 
half hour of friction failed to hatch eggs, but the larve when freed by 
picking off the operculum showed two, slight movement; one, no move- 
ment, and one sufficient movement to get out of the opened shell. 
On the fourth day the larve in eleven eggs were all active, but had 
to be freed by picking off the operculum; the same was true up to the 
seventh day, the only difference being noted in greater maturity and 
size of larve. 
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