THE AMERICAN DOG TICK. 193 
dog August 10, 1909, measured 15.5 by 11.2 by 7.4mm. 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. 
TaBLE XC.—IJncubation and longevity of larve of Dermacentor variabilis. 
IN LABORATORY. 
Temperature during in- 
Mini- cubation. 
mum 
. incu- Larva 
eee ee en All larve dead. lon- 
eposited. began. tion ee Aver- 
gevity- Iyraxi-| Mini- age Total 
pe- r H effect- 
I mum.|/mum.|} daily} ~. 
riod. eer |) bc 
1908. 1908. Days. Days eA cee ee wae 
April. <2 Mayilsoscc- =. BS oper rer are erence eke raitatetores enh arcs ereroereles 86 47 | 70. 41)1, 041.50 
WWNE AK <3 =| - June 28....-- 25|p OctiA G08" os = se coma sec mceiece 98} 91.5} 69 | 80.98} 949.50 
June 10.....- bi Aer Seeoeoos ZA Oct GGUS ee ese sae 2 see oes 95) 91 69 | 80.33} 895.75 
June 12.....- ified yea eee Sal OGtsr4A G08 ee aes sie cemace 82} 93 70. 5} 81. 31/1, 264. 25 
Dyes eee ee Tully 255 on oe 2A May sl (al O09. Sete see as acces oe 296} 95 70. 5) 83.26] 888 
dailyaGsen ea Uiliye2seee ae Dale MMe OF NG0 9 ee cies eine a= 318} 95 74 | 83.86} 899 
ini he (Gesebece Gesoe GOeER act Zi sume 27, 1909 Fe a eace<ea-se en 335} 95 74 | 83.98] 860.50 
divi; LIEB eeee July 305-2 =e 20] Apr. 16-May 7, 1909)-./2- ah ss=5 260-281} 95 74 | 84.26) 825.25 
iby 2s. See AMIE S = So 3: 21 Noe SANG 1OO8o. 2 oss fee BS 100-107] 95 74 | 84.29) 867 
Tilly 15s... ING G21 5 eae Dil Mayas (beef G09 see ee eee ae 277-284] 95 | 76.5] 85 882 
ooyAT S252... AUg..6. 2.45, < 21) SunewO; 19095. - 22-2. - oF ee 308) 95 76 | 85.18] 886.75 
Aug. 16,1909 | Sept. 8, 1909 24| Jan. 28-Feb. 25, 1910.........- 142-170) 110 77 =| 89.39)1,112. 75 
Apr. 25,1910 | May 31,1910 37| July 19-Aug. 4, 1910.........-- 49-65) 93 43 | 73.89)1,143 
May 7,1910] June 6,1910 Zl bMarstsoiiees sae). ee 282} 100 | 59 | 76. 62/1, 042.25 
May 9,1910| June 8,1910 31| July 19-Aug. 4, 1910..........- 41-57) 100 59 | 77. 42/1, 067 
May he 1910 } June 11,1910 26| Meps os lOUlse et. ee ee ean : 239] 100 60 | 79.30) 943.80 
OUT OF DOORS 
Apr. 13,1906 | May 25,1906 4D | Pe ater mec eatee.cee Moet ae Mace seta op Seales 93 41.5] 68. 73/1, 106 
May 5,1906| June 8, 1906 Siete yl NE eT ae a ee eee 93 | 42 | 72.94|1,048 
June 25,1907 | July 21,1907 Fy | eae EAL PE TS OR ee 99 | 63.5] 81.30]1,034 
Aug. 17,1908 | Sept. 9,1908 Dal NV 29 5 GOO eye xc ehs fat es ae on 262} 100 64 | 80.85] 908. 40 
anne 2 51910 | July 951910')...--- Dees 2s-oly LOLs ee see eee Gy coil) ee eariacs| iscrtores| Memcos= 
9, 1910 | Sept. 4,1910 Pgh eh ela yal Ke URS Re ee ae 194] 105.6} 66.7] 86. 49/1, 174.25 
Rte. fe NOON Peer doeeaess- DD thee cate tae tienieweerane tes cel eae means 105.6] 66.7} 86.5 |1,087 
The larva (Tables XC-XCITI).—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——13 
