THE AMERICAN DOG TICK. 193 
dog August 10, 1909, measured 15.5 by 11.2 by 74 mm. It began 
depositing on the sixth day and continued depositing for 23 days, 
during which time 6,855 eggs were deposited. This is the maxi- 
mum number of eggs recorded by us for the species, but Prof. H. A. 
Morgan (1899) has recorded 7,378 as being deposited by one tick 
between May 8 and June 26. The minimum number of eggs depos- 
ited by 11 ticks was 2,808, the average 4,568. 
The minimum incubation period for eggs kept in tubes out of doors 
was 24 days. This record was made on eggs deposited August 17, 
1907. Eggs kept in the laboratory at a mean temperature of 84° F. 
hatched in 20 days. An effective temperature of at least 825° F. 
appears to be required for their incubation. 
TaBLeE XC.—IJncubation and longevity of larve of Dermacentor variabilis. 
IN LABORATORY. 
Temperature during in- 
cubation. 
Larval 
Eggs Hatching All larvee dead lon- 
depos began J : } a 
sa gevity- |raxi-| Mini- pe, otal 
mum./mum.| daily eek 
ean| ive 
1908. Days. | °F.| °F. | °F. | °F. 
Ce Oe Cee ae fee 86 47 | 70.41)1,041.50 
Jone 4... ....} June 28. ....- Ue A Se ee 98} 91.5) 69 | 80.98) 949.50 
perry er Sy ce =. Sh Se as See ee ee 95, 91 69 | 80.33} 895.75 
sumo tc...) saly 24... - ON ae se ee ee §2; 93 70. 5} 81.31}1, 264. 25 
ee ee Ter EY 2. Dg y Ro eS ee eee ae 296} 95 70. 5] 83.26] 888 
1) OA Uae (Bis gi-7 ee ame Pre AL | eee. See eee 318} 95 74 | 83.86} 899 
2 SA eee BA Ce St TE Be Op ee ee 335} 95 7 83.98] 860.50 
aes =...) July 30. . 2<.. Apr. 16-May 7, 1909. .........- 260-281} 95 74 | 84.26) 825.25 
Ei Fae eS Vwi f 35 Oe Ngw25-16: 1908! — 8 ee 100-107} 95 7 84. 29 7 
July 15....... myi oe... 277-284] 95 | 76.5] 85 | 882 
Ug’ UT SV 1 a ee ae 308} 95 76 | 85.18) 886.75 
Aug. 16,1909 Jan. 28—Feb. 25, 1910........-- 142-170; 110 77 | 89.391,112.75 
Apr. 25,1910 July 19-Aug. 4, 1910........-.-- 49-65) 93 43 | 73.89)1,143 
May 7,1910 (I |) ee ee ee eee 282) 100 59 | 76.62)1, 042.25 
May 9,1910 July 19-Aug. 4, 1910.........-- 41-57| 100 | 59 | 77.42/1,067 
May 17,1910 Wels. MEUM eee oe ee | 239) 100 | 60 | 79. 30) “943.80 
i 
OUT OF DOORS. 
Apr. 13,1906 | May 25,1906 3 OR oe ae Se be os 73 1,106 
ay 5,1906| June 8, 1906 “- SEES A PS FP 2.941, 048 
June 25,1907 | July 21,1907 7 CRG ig ae SE RS Be NE Se Cea .5} 81.301, 034 
Aug. 17,1908 | Sept. 9,1908 Pe ae ee ee ; 85) 908. 40 
June ?,1910] July 9,1910].-...-- Cee 2 ee eT pe ee eg eed ae See ea (em eee 
Aug. 9,1910} Sept. 4,1910 By a a ee . 491,174.25 
Aug. 11,1910 |..... py 72) |e aif NR ear SRT 4 Roary hahs eee .5 ‘seve 
The larva (Tables XC-XCII).—The greatest longevity of the larve 
of this species recorded by us was 335 days. This lot of larve 
hatched out June 27, 1908, and was kept in a glass tube on moist 
sand in the laboratory. One lot of larve kept in a tube out of doors 
lived 262 days. The incubation and larval longevity records given 
in Table XC are a few from a large number of records selected to 
illustrate the variation in these developmental periods. As may be 
21448°—Bull. 106—12——138 
