AA BULLETIN 1369, U. S. DEPARTMENT OF AGRICULTURE 
TABLE 2.—IJncubation of eggs of Hypoderma lineatum in situ and in incubator 
at Dallas, Tex— Continued 
Nein | Air temperature _ 
her Inecu- 
Deposited of Place and method Date of hatching bation = 
: period |Mavxi-| Mini-}-. 
eggs . Soe Se Mean 
Joo ps Se es RS aE ee eee ee 
1921 i 1921 Days 90" | Pee OF 
Marat5, 11-30'asan=3|5) 704) aie bator 225s a Mar. 18,9 a.mtop.m__ 3— | 98 98 98 
0. sae eee 155°] -Cansieet ==. War18, Oa. mS 3— | 87 63.5 |- 74.6 
Mar. 16, 5 p. m_-__- AOA Calf’sleg. wees 74 War: 10, sara aés - s2eeees - 24— | 87 68.5 | 74.5 
1D 16o-Incoabapors-= =~ ae Mar. 19,9a.m.to12m_| 234— | 98 98 
1922 1922 | 
Mars 155415 ppm. =|— 154 Incubator = Vin 185 bo. pe al == = 3— | 30 90 90 
Mar. 16, 2.30 to 2.45 re (ees dO neass yFea sera Mar. 19, 10 a. m. to 4.40 3 Se $0 30 
p. m. p. m. | 
er 20, 12.50 to 85 | Cow’s heels: 2. = 2 Mar. 24, 10.30 a. m______ | ~4— 1 84 | 36 | 648 
1.10 p. m. E : 
D0 Se SE (4:\ Incubator--2- === Mar. 22, a.m. tc p. m____| 3 | 90 =| 90 20 
Mar. 15, 3.13 to 3.15 Soule. oe OSes ES Mar. 18, 11 a. m. to 1 3— | $0 g0 | 90 
De 1: p. m. a 
Mar 285 3:1570'3230 |e t72e doe =< tite asa Mar. 31, 8a. m. (before) | 214) 90 | 90 |° 90 
p. m. | | f0-8.15 aie 
| | 
1 Hatching de‘ermined by the kicking and rubbing of host, some checked by actual examination. 
Glaser (29), without making it clear whether he is dealing with 
EH. bovis or H. lineatum, states that he has observed the incubation 
period of eggs clipped from the host to be 12 days. He also says 
that on living animals development is completed in less than 3 full 
days. Hadwen (36), basing his statements on observations in 
Canada, states that the eggs when removed from the host hatch 
in about 7 days, the shortest period being from 4 to 5 days, but 
apparently he made no observations on the incubation of eggs on 
the host. ? 7 
The writers have made few exact observations on the incubation 
period of H. bovis. At Middletown, N. Y., 2 out of a lot of 6 
eggs deposited on a calf June 8 at 5.30 p. m. had hatched on June 
11 at 12.15 p. m., a period of approximately 3 days. These were 
left on the host. In one instance in which eggs were sent by mail 
from a northern State to the Dallas laboratory and placed in an 
incubator they hatched in less than 7 days after collection. Car- 
penter (77) observed eggs attached to a host to be hatched in ~ 
slightly less than 4 days. 
The writers, in their work with reared flies, have obtained a 
considerable number of eggs from females which were not as- 
sociated with males, and in none of the cases was there any hatch- 
ing, indicating that parthenogenesis does not occur in this species. 
The percentage of viable eggs deposited by fertilized females 
seems to vary considerably. Im some instances a hatch of almost 
100 per cent has been observed, whereas in other cases the examina- 
tion of a series of eggs showed a hatch of less than 50 :per cent. 
It seems certain that the percentage of the hatch is higher when 
the eggs are deposited and allowed to remain on a host than when 
they are removed and placed in an incubator, although in a few in- 
stances a hatch of above 90 per cent was obtained among eggs 
kept in an incubator. 
In general it appears that the eggs attached lowest on a hair 
hatch slightly earlier than those toward the distal end. When this 
= 
“y 
