﻿THE CATTLE GRUBS OR OX WARBLES 



43 



64 hours to 10 da5^s. It is evident tliat the period of iiiGubation is 

 markedly affected by temperature. With eggs deposited on a host 

 this would vary according to their proximity to the skin and tlie 

 insulation from air temperatures by the hair. With normally placed 

 eggs 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. lineatnm. 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 larva?. 

 It will be observed that in one instance irritation was evident approxi- 

 mately 2^4 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 Hi/poderma lineatum in situ and in incubator 



at Dallas, Tex. 



Deposited 



Num- 

 ber 

 of 

 eggs 



1917 



M;ir. 7, 4-30p. m... 100 



Mar. 8, 4.30 p. m... 20 



Mar. 14 175 



Mar. 23 2 lOO 



1918 



Mar. 162 



Mar. 26, p. m.2. 



1919 

 Mar. 10 



Mar. 10, .5 p. m_ 

 Mar. 12' 



Mar. 142 



Mar. 16, p. m... 

 Mar. 19, 5 p. m. 



Do 



Do 



Mar. 20, 1 p. m. 



Mar. 21, 11 a. m.K.. 



Mar. 27, 2..30 p.m.. 



Mar. 27, p. m 



Do 



1920 

 Mar. 6, 4 p. m.. 



Do 



Mar. 10, .5 p. m. 



Mar. 12, 5 p. m. 

 Mar. 18, .5 p. m. 

 Mar. 22, o p. m. 

 Mar. 28, 6 p. m. 



160 

 20 



65 

 175 

 40 



40 

 60 

 100 



25 



37 



3 



2fW 



77 



80 

 21)0 

 52 



200 

 KX) 

 2.^0 

 95 



Place and method 



Calf'sleg 



do .-. 



Incubator Mar. 15-1 J 

 do.. 



...do. 

 ...do. 



Calf'sleg. 



Calf's belly... 



Vest pocket and In- 

 cubator, 

 do. 



Cow's legs and body. 

 Incubator 



Calf's belly 



Calf 



On calf and in 



bator. 

 Incubator 



.do. 



Cow's body. 

 Calf'sleg 



Calf 

 Calf 

 Calf 



s heel and belly . 



at hock 



s shoulder 



Calf: 

 Calf! 



Calf 



Calf's legs and belly. 



"s heels 



"s shoulder 



Date of hatching 



1917 



Mar. 11 1 



do 



Mar. 17 to 18.. 

 Mar. 25 



1918 

 Mar. 18, a. m. to p. m. 

 Mar. 29, a. m 



Mar. 16'. 

 .do. 



Mar. 22 to 24. 



Mar. 22 



Mar. 201 



Mar. 22, 2.30 p. m., to 

 Mar. 2.3, 11 a. m. 



Mar. 22 



Mar. 22, p. m 



Mar. 24 



Mar. 23, 7 p. m. to Mar. 



24, a. m. 

 Mar. 30, 6 p. m. to 10 



p. m. 



Mar. 31, p. m 



Mar. 31 ' 



1920 



Mar. 9, 5 p. m.' 



Mar. 9, p. m.> 



Mar. 15, u. m.,' one-half 



hatched. 



Mar. Ifl' 



Mar. 22, a. m.' 



Mar. 2fi' 



Mar. 31, 6.30 p. m., to 



Ai)r. I, 3. 15 a. m. 



Incu- 

 bation 

 period 



4- 

 3- 



3-f 

 2+ 



2+ 

 2K+ 



6- 

 6- 

 10+ 



8+ 



4- 



3 to 4 



3 

 3- 



4- 



2-34- 



3-+- 



4- 

 4- 



3- 

 3- 



4- 



4- 

 3-3. 5 



Air temperature 



Maxi- 

 mum 



F. 



84 



77.5 

 77.5 

 81 



81 

 79 

 90 



81 

 81 

 90 



90 



<)() 



93 

 93 



55 

 55 

 76 



76 

 81.5 

 80 

 90 



Mini 

 mum 



op, 



30 

 30 



85 

 85 



37.5 

 37.5 

 37.5 



40.5 

 40.5 



35. 5 

 35. 5 



W. 5 

 20.5 

 36 



36 

 42 

 46 

 40 



Mean 



p_ 

 65. f 



3.4 



96.5 



60.5 

 60.5 

 62.7 



63.8 



61 



90 



6.3.2 

 63.2 

 90 



60.3 

 (10. 3 



38 

 38 



61. 1 



61 



63.4 

 61.7 

 63. 7 



' Hatching determined by the kicking and rubbing of host, some checked by actual examination. 

 ' Collected from animals Infested under natural condltlona. Exact time of deposition unknown. 



