THE ROCKY MOUNTAIN SPOTTED-FEVER TICK. 169 
30 to 50 days after they are deposited. Records made by Mr. W. V. 
King show the incubation period to vary from 34 to 51 days in the 
Bitter Root Valley in Montana. 
TaBLE LXXVI.—Preoviposition, incubation, and larval longevity of Dermacentor 
venustus. 
| Temperature during incuba- 
Pre- | Mini- tion. 
peak d ovi- | mum Larval 
“entie | Deposition | posi-| Hatching |incu-| All larvee | “4, 
emale ; : on j | T 
d d began. tion began. ba- dead. avit _ j|Aver otal 
ropped. peri- tion S°V"'Y-) Maxi-| Mini-| age |effective 
od. peri- mum, | mum. | daily | temper- 
od. mean.) ature. 
Tl Sate ESS Oy ee eee Ps Pace) Ses fe Sells 
1908. 1908. Days 1908. Days. | RE he Oe OB ll aie 
June 6.. June 24.......- 7 eee Ae 91.5 69 |80.8 | 718.25 
WHE 72 sete sl ao a52 aoe dqscts. Me See ae ee 91.5 69 |80.8 680.5 
Fune 13.....-|-.....| June 28.......- TG) SURE y gees RS 91.5| 71 (81.4 | 614.75 
i Sy SB VARS be "| ee me) Pete coe eceeass 90 71 80.8 641.75 
1909. 1909. 1909. 
1July 1| Before July Is") daly 31.2... .525 18+ — Sept. lg Ses, a Be | nee a ee 
14. s 
1 Junell | June 27...... 16:| July 452.22"22- 19 Aug, 26-Sept. 42-62 | 102 47 \91.8 917 
1910. 1910. 1910. 
are 28) ADT Teo. cess 10) May Ge 2s 34 July 19-Aug. | 70-87] 91 43 |70.49 | 744.66 
5. 
Lr cee fal (REG ge 10" Mayriot 2a: 33 ci ee July 61-| 95 51 |74.6 979.6 
Apr, 12) Apr. 18.....- Gilece sa MO ee. oe 32 inby. 19-Aug. | 61-78 | 91 43 |70.33 74. 56 
De. ..t) Ape. 2s. 10 |) ‘May 25:.:.-... 34 ae eee cee 75 | 91 43 74.8 |1,081.2 
-1Apr. 13 oe. | ia es qyere . 5 36 Aug. 5-20....| 72-87] 91 43 |71.78 |1, 036. 08 
Apr. 26] May 2....... 6| May 31........ 30 uly 20-Aug. | 50-66 | 91 59 |71.66 | 859.8 
1May 1] May 10...... 9 | June 6.... 28 way, 21-Aug. | 45-60 | 100 59 |77.02 | 952.56 
1 May 14| May 23...... Ou MUNG Oe se. BE he: 25-31....| 74-80 | 100 60 |79.64 | 769.44 
1June 4] June 13...... 9°) June 29: 20.5. h Lf Sept. 29... -...< 92] 97 69 |84.37 | 703.29 
Ges HOw ess. oy ae ol  ge eae eee 19 Aug. 25-31...) 55-61 | 97 69 (84.59 | 790.21 
July 16 | July 25...:.. 9| Befowe Aug. | 17— | Sept. 24-Oct. | 45-56 | 104 79 |90. 19 | 755.23 
10. 5. 
1911. 1911. 1911. | 
Mor.) 20 Apr. 4...25-- hile Magy Ts 292s 41 | Ce Pe clyde 89 §2 (71.7 |1,1%6.7 
} 
1 This tick was picked from the host. 
The larva (Tables LXXVI-LXXVIII).—The longest time between 
the beginning of hatching of a lot of eggs deposited by a single female 
and the death of the last larva was 92 days. In this case the eggs 
and larve were kept on moist sand in a tube in the laboratory. 
Hatching began on June 29, 1910, and the last larva died on Septem- 
ber 29. In the majority of cases in a series of over 200 observations 
the last larva died within 85 days from the time the first eggs in the 
lot hatched. In a number of lots of eggs separated from the parent 
female the day they were deposited the larvee all died within 2 
months after hatching, even though kept under the most favorable 
conditions. In a number of instances larve which hatched the 
latter part of July and early in August all died within a month. 
Cooley’s experiments in Montana (1909, p. 102), as well as tests 
made by we ¥i King in that State, indicate that the longevity of 
larve in Montana is about the same as that observ ed by us at 
Dallas, Tex. 
On account of the fact that the period of deposition is frequently 
longer than the incubation period, in warm weather the larve begin 
