﻿44 BULLETIX 1369, U. S. DEPAETMEXT OF AGEICULTUEE 



Table 2. — Incubation of eggs of Sypoderma lineatum in situ and in incuMtor 

 at Dallas, Tex. — Continued 





Num- 

 ber 

 of 



eggs 



Place and method 



Date of hatching 



Incu- 

 bation 

 period 



Air temperature 



Deposited 



Maxi- 

 mum 



Mini- 

 mum 



Mean 



1921 

 Mar. 15, 11.30 a. m 



70 



155 



40 



16 



15 

 45 



85 



74 

 32 



72 



Incubator. ' 



1921 

 Mar. 18, 9 a. m to p. m. _ 



Mar. 18, 9 a. m.i 



Mar. 19, a. m.i . _ . 



Days 

 3- 

 3- 



2M- 

 2^4- 



3- 

 3 



4- 



3 

 3- 



2M 



p 



98 

 87 

 87 

 98 



90 

 90 



84 



90 

 90 



90 



° F. 



98 



63.5 



63.5 



98 



90 

 90 



36 



90 

 90 



90 



o p^ 



98 



Do 



Calf's feet 



74.6 



Mar. 16, 5 p. m 



Calf'sleg 



74.5 



Do .. 



Incubator - 



Mar. 19, 9 a. m. to 12 m . 



1922 



Mar. 18, 1 to 2p. m 



Mar. 19, 10 a. m. to 4.40 



p. m. 

 Mar. 24, 10.30 a. m 



Mar. 23, a. m. to p. m 



Mar. 18, 11 a. m. to 1 



p. m. 

 Mar. 31,8 a. m. (before) 



to 8.15 a, m. 



98 



1922 

 Mar. 15, 4.15 p. m 



Incubator .- _-. -- .. 



90 



Mar. 16, 2.30 to 2.45 



do 



90 



p. m. 

 Mar. 20, 12.50 to 



Cow's heels ... 



64.8 



1.10 p. m. 

 Do 



Incubator 



90 



Mar. 15, 3.13 to 3.15 



_— do... 



90 



p. m. 

 Mar. 28, 3.15 to 3.30 

 p. m. 



do 



90 



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 

 H. hovis or TI. lineatum^ states that he has observ^ed 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. 



The writers have made few exact observations on the incubation 

 period of H. iovis. At Midclletown, N, Y., 2 out of a lot of 6 

 eggs deposited on a calf June 8 at 3.30 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 (17) 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. In 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. A'S^ien this 



