LIFE HISTORY OF CATTLE TICK. 19 
TasLe I1.—Period of incubation of Margaropus annulatus at Dallas, Tex., 1906, under 
various conditions. 
| Minimum | | Minimum 
Eggs deposited. Hatching. | incubation || Eggs deposited. Hatching. | incubation 
period. | | period. 
|) Days. || Days. 
AD Ke per assess < VIC See eee a= | Gia AUIS Alas ars eee 28 
‘Neves OS Beene I Migiv; 30 ooh 8-5 Onan | eA ee Ace ce) Se aa 3 b24 
Apr. 15 Dv i iy A a ee CALA ATI ES a eee 3 b 23 
PATINA yeti Sa. A eb ovetw: Vee ea ae GOON PAUP See az eet a 32 
Misa sien nek Ja Jumesl4-* oe Ai Gon |e aslo sey e aaa b23 
Wa Gl ee ee [fybire ve bauer een pe weal UDO) Ni ACO) ee Se c24 
IMIG ORL ae eer nigeaes JUNC QE eae 2s). H WON ANG. Dee Ales a23 
EIN C 1 eae FUMEWG Ss eles | GORE AN Gy 22 oe ae atsae c24 
Misvaalec< ees. ine ease an | GOR || mAu ee 4 a oe b24 
UTI Oe eee ate oe NbN asi8 Je So toe ee GD Teal AUS Omnis ce te oe b24 
Tit: Sik an ae Ti liya bee ae Sone | CIGu eos ee c25 
STOLL = ate i oss Dall varieees =e eee os | DO Tale ANE) 2S Sp eee ae a27 
PURLEL Al ee = ses </> 5 TUL VALS eee COOSA WTS (:5 0) reall Ie ea ee ¢ 23 
MMC oe 5 Jule Se es = | OBS Steyoll te Ne eee Beet | b 24 
lbs (2, ul yes Gee seers @23\| Sept. 1.---.---.--. a27 
pum wes. es Sek Oily pul Geese ees GQat He SODibe ass 2s. scene c25 
dime s0u. fs. 2-222 Jilly 20 Meee ee BOT Sop tuoee ten 2 sate. c29 
Dyes hese Sade te Daily Zoe eee B22 SOP Ono: seca es b 32 
Pinliygs 20S Se orsectecis © Anes Oe Sates b 22 | Sept. 9....2....... a37 
‘Gila Osta Hgneee Tues STS | COG NeSep tiltecenes eee c41 
JUlye QOS oh ese ce PAC eA Sota Sr c24 | Sept. tse cane eces b 43 
NEU OE) a aes ae TA 2D o seeps WOR RISI=| Olin te ae Bee sere a53 
iibthy Biles eee ae Aiea OO Meta See COPA NSepital Saeeen tee we b76 
SUbY tell mS ae Aug. 237 - 2a) Sept. (8.2205. 2s. a76 
VHS a a ee Sept: 4e-cos e222: OP ipsa Pia la eo we b148 
ENTE 0) sei eae Sep tesseeee se = c23 
a The eggs were placed in open-bottom test tubes in sand in the open air. They were protected from 
the direct rays of the sun at all times by a cheese-cloth screen. Up to 11 a. m. they were 
within the shade of the house. 
b In open-bottom test tubes in soil exposed to sun at all times. 
¢ In open pil! boxes outdoors protected from sun and rain at all times. 
RELATION OF TEMPERATURE TO INCUBATION. 
In the series of experiments just referred to accurate data on tem- 
perature were obtained. Standard maximum and minimum ther- 
mometers kept in an instrument shelter were used. In Table III 
the records of temperatures are given together with the average 
incubation periods for the various lots of eggs under observation 
during different months. The data show that there is an intimate 
relation between temperature and the period of incubation. The 
shortest average minimum incubation period (23.4 days) occurred 
when the average temperature was highest (80.2° F.). The longest 
average minimum incubation period (137 days) occurred with the 
lowest average mean temperature (53.2° F.): Between these ex- 
tremes there is a graduated correspondence between temperature and 
incubation. 
