THE CATTLE GRUBS OR OX WARBLES A3 
64 hours to 10 days. It is evident that the period of incubation is 
markedly affected by temperature. With eggs deposited on a host 
this would vary according to their proximity to the skin and the 
insulation from air temperatures by the hair. With normally placed 
egos the basal ones on the hair are usually very close to the skin, 
but in the case of eggs deposited on fairly long hair the distal ones 
may be half an inch away from the skin. 
Table 2 sets forth a number of observations on the period of 
incubation of eggs of H. lineatum. Many of the records are only 
approximate, the time of hatching having been determined largely 
by the irritation of the host produced by penetration of the larve. 
It will be observed that in one instance irritation was evident approx1- 
mately 284 days from the time the eggs were deposited on the legs 
of a calf. This incubation period was almost exactly the same as 
that observed on a portion of the same batch of eggs placed in an 
incubator at approximately 98° F. The writers’ observations indi- 
cate that the usual incubation period on the host is from 3 to 6 
days, probably most of the eggs hatching toward the end of the 
third day and early in the fourth. 
] 
TABLE 2.—Incubation. of eggs of Hypoderma lineatum in situ and in incubator 
at Dallas, Tex. 
NGAGE r Air temperature 
neu- iia 
Deposited pe Place and method Date of hatching bation Alder 
1917 1917 DOYS NS TRE OH, OE. 
Mar. 7, 4.30 p. m___| 100 | Calf’sleg_.______.____- UN Meer ree lel ieee Si ie 4— | 84 30 65. 6 
Mar. 8, 4.30p.m___| 20 |----- GOES Sah as wee es me Ses Os ee en 3— | 84 30 63. 4 
Nici Arabs 6 we a 175 | Incubator Mar. 15-18_| Mar. 17 to 18___________- 3+ | 87 85 86 
Migros ce ae ets te NO) Leases (6 \o) Ss ah tages De ales ee te dA LS a A es RN a 2+ | 87 85 86 
1918 1918 
Vie G2 eee a Oe (3 Koei ean Mar. 18, a. m. to p. m__- 2+ | 97 96 96. 5 
Mar. 26, p. m.?_.__- 20. /b2- 2 COs eee ee Mian. 295 a.m) 2225-2 2 8 - 234-++ | 99 97 98 
1919 1919 
AAU rat Q)gs ala rae aa Gon Caliicilepet sees ANA Ga ee BGS see anaes a es ee 6=— | 77.5.) 37.5 | 60:5 
Mar. 10, 5 p. m____- 175 | Calf’s belly______-___-- Ea Nee Cae SR aR er oe eli | aie) It COE 
Mla )2 0 oe Se _.| 40] Vest pocket and in- | Mar. 22 to 24____________ 10+ | 81 Sie feb ABV? 11 
cubator. 
Mian W4eaiei eye 40g E32 GOA Rs oy SEG INT aT DD NR an 8+ | 81 40.5 63.8 
Mar. 16, p. m______- 60 | Cow’slegs and body__| Mar. 201_______________- 4— | 79 40.51 61 
Mar. 19, 5 p. m__--- 100 | Incubator____-__-.___- Mar. 22, 2.30 p. m., to] 3to4 | 90 90 90 
: Mar. 23, 11 a. m. 
1D YO) 5 eee ean 25° | Calf’s belly 2.22. === 2: INVA Lee pe) ns aie SS ae ed 3 81 40.5} 63.2 
OM eee tenes Stale Galt cee pe per. eee Mita 22) pss eee 3— | 81 40.5 | 63.2 
Mar. 20, 1 p. m____- 3 oe ealf and in incu- | Mar. 24________________- 4— | 90 90 90 
ator. 
Ware 2teileaatm2.42| 2310! Inculbators---. 2.20.4 .- Mar. 23,7 p.m. to Mar. | 2-3-+ | 90 90 90 
24, a. m. 
Mars27, 2:30 pim~=.! , 260.|i_._- (GLO Mar. 30, 6 p. m. to 10 3+ | 90 90 90 
p. m. 
Mar. 27, p. m______ 77 | Cow’s body2_-.---_ 2 Wake yes Bile oy anise e Ge ce 4— | 93 35.5 | 60.3 
IDOE eee nea ae TN ORM Glee OS ea Mare oie lisseetrn se hers oe se 4— |} 93 3040 60. 3 
1920 1920 
Mar. 6, 4p. m______ 80 | Calf’s heel and belly__| Mar. 9, 5 p. m.1________- 3— | 55 20.5 | 38 
1D oe wee: ee See 200 | Calf at hoek___________ Miar9;,p smd 2 3— | 55 20.5 | 38 
Mar. 10, 5 p. m_____ 52 | Calf’s shoulder_______- Mer. i 2 m.,! one-half | 434— | 76 36 61. 1 
atched. 
IME Y RSE Tih esac eee 200 | Calf’s heels___________- Meare Ges ed aie: 4— | 76 36 61 
Mar. 18,5 p. m_____ 100 | Calf’s shoulder_______-_ IMMUNE OPA tested tne e Moan See 334— | 81.5 | 42 63. 4 
Mar. 99. 5 psc 2 _ PI5O WE Calies me ay thas. Mar: 2Gte Renee 9s 4— | 80 | 46 61.7 
War: 28, 5p.m._.__- 95 | Calf’s legs and belly___| Mar. 31, 6.30 p. m., to | 3-3.5 | 90 40 63. 7 
Apr. 1, 3.15 a. m. 
1 Hatching determined by the kicking and rubbing of host, some checked by actual examination. 
4 Collected from animals infested under natural conditions. Exact, time of deposition unknown. 
