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. 
Taste LXXVI.—Preoviposition, incubation, and larval longevity of Dermacentor 
venustus. 
| Temperature during incuba- 
3 ini- tion. 
Date a a ere 
Foun Deposition | posi-| Hatching |incu-| All larve [45)- 
a oA began. tion began. ba- dead. Beit Aver-} Total 
ROE Re peri- tion 8eVILY-| Mraxi-| Mini- age jeffective 
od. peri- mum. } mum, | daily | temper- 
od mean.} ature. 
1908. 1908. ‘Days. 1908. Days ORE eevee ike eal peaweents 
Ine 1G see ale i085 June 24..22...- LO Me | yee epee nia, No's| oe 91.5 69 |80.8 718. 25 
MUNG Sate oe mecieeieel- (OE Ree aes 1 a SSR aaa mee el aoe mre 91.5 69 |80.8 680.5 
Atine tsesese 144 2c | UNS 28 ose. oe GE |S etree otal saan ae 91.5 71 \81.4 614. 75 
UME WD: cosas cee |Pallbya Ls .Sac a. il?) BOM oe She OS 9 See Bie 90 71 |80.8 641. 75 
1909. 1909. 1909. 
1July 1 Bers July 1S | oulyzolee- == nce 18+ Belore Sept. AGRI Ws cee cial eer elcteis| 2 settee | nero mami 
1 Junell Fhe Bececiac Gu eantabyters = ese 19 ie 26-Sept. 42-62 | 102 47 |91.8 917 
15. 
1910. 1910. 1910. 
EMare28) | CAI! femsccie LON) Mary 10 In 34 J uly, 19-Aug. | 70-87 | 91 43 |70.49 | 744.66 
Atprn fe ADE. Leones 10 | May 19......-. 33 Beiore July 61- | 95 51 |74.6 979.6 
Apia te) ears 18. .36. = Galewaiers (6 {ol aera 32 suly 19-Aug. | 61-78 | 91 43 |70.33 | 874.56 
DOs ce | ADs eee cce sly 10))|| Mayi2bos ses =. 34 ee Sites 75} 91 43 |74.8 |1,081.2 
1Apr.13 | Apr. 20...... ls don sceaes 36 Aug. 5-20....] 72-87] 91 43 |71.78 |1,036. 08 
Avot) 26!) Moy 20.2. ..- 6. ayisi seen 30 july 20-Aug. | 50-66 | 91 59 |71.66 | 859.8 
1May 1] May 10...... 9} June 6.... -| 28 July 21-Aug. | 45-60 | 100 59 |77.02 | 952.56 
1May 14] May 23...... 9) une 1a ea ot 2 nts 25-31...) 74-80 | 100 60 |79.64 | 769.44 
1June 4] June 13...... 9) | June 29 ea 17 Sept.292-c-- 92] 97 69 |84.37 | 703.29 
EJOnEShlis< 1 < doyeeees bialeniiliy, deen eee 19 Aug. 25-31. ..| 55-61] 97 69 |84.59 | 790.21 
1July 16 | July 25...... 9| Before Aug. | 17— cept. 24-Oct. | 45-56 | 104 79 |90.19 | 755.23 
0. 
1911. 1911, 1911. 
Manse 27)\" Apr 4c .i5-. | 8) |) May, 140-38. = AN Al Paes ihe Sees oe ole 89 52 |71.7 {1,176.7 
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 inthe 
lot hatched. In a number of lots of eggs separated from the parent 
female the day they were deposited the larve 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 W. V. King in that State, indicate that the longevity of 
larve in Montana is about the same as that observed 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 
