2°00 LIFE HISTORY OF NORTH AMERICAN TICKS. 
which dropped from a host on July 27. These ticks were kept at a 
mean temperature of 85.4° F. The period of deposition ranged from 
15 to 37 days. The length of this period, as well as that of the preovi- 
position period, is materially affected by temperature, the high tem- 
peratures producing the shortest periods. The maximum number of 
eges deposited by 1 tick was 3,392 in the lot of 12 females observed; 
the average was 2,784. 
The minimum incubation period for eggs in the laboratory at a 
mean temperature of 85° F. was 24 days. An effective temperature 
of 935° F. appears to be required for incubation. 
TaBLE XCVI.—Preoviposition, incubation, and larval longevity of Dermacentor nitens. 
OUT OF DOORS. 
Temperature during incubation. 
Date ae 5 
engorged| Eggs |Hatching ee i Bees pein l 
deere OUSTEET | T0252 period. dead. | gevity. | Maxi- | Mini- pies com 
aes aber mean. tive 
1908. 1908. 1908 Days. 1908 Days. pels uae eH eae 
Apr. 22| Apr. 29| June 5 38 | Aug. 15 71 91 43 73.2 | 1,149.2 
DOW | i. dolce June 6 39 | Aug. 7 62 91 43 73.5 | 1,187.7 
May 17| May 21 | June 20 31 | Aug. 14 55 93 62 79. 3°) 1,125.3 
May 18| May 26 | June 24 30 | Aug. 15 52 96 62 80.4 | 1,120.6 
May 19 doesce - June 26 32 O22 50 96 62 80.3 | 1,195 
May 20| May 27 | June 28 33 | Aug. 19 52 96 62 80.3 | 1,232.5 
May 22| May 26 |...do..... 34 | Aug. 28 61 96 62 80.3 | 1,268.2 
May 26} June 2] July 1 30 | Aug. 29 59 9657 62 80.5 | 1,124.9 
IN THE LABORATORY. 
a A May 2) June 1 Bille Lv eee eae, ts Seek ees oe 87 56 toe 999 
satewio ss May 3) June 3 Oke pees een eee ce oe 88 56 75.8 | 1,049.5 
AMS arse May 9j| June 5 DR | Wee cna Sela ee aes 88.5 65 77.5 966 
ee ee May i0| June 6 DA Sak Se eee | ie igaee 88.5 65 77.8 957 
Es eee May 13] June 8 PAB) Sosa renee SM Oe pa te ar 90 65 78.3 952.8 
op. © pple May 14]| June 9 7 fa | eee? eh ea Pe aes ee ey 90 65 78.7 963.3 
ye A eee Maye 5) edoees- AG yi al ee Ne ea 90 67 79 935.3 
ay Le ae July 31 | Before essithan'30 | Decs ui -Abouti98)|S-e 22-0 52|o- 42 eases) aceemse ae oe eee 
Aug. 29 
Amare Auge, 22-20). 231 bess than 28" Nove 26) |PAIDOUT SO) Saas e eee eet aera | sate see ae 
Saeaice ores Aug. 6] Aug. 29 24 | Nov. 26-| 89-117 99 73 85.25 | 1,014 
Dec. 24 
ee Ang. 9 | Sept. £ 24| Oct. 26-| 55-77 96.5 73 84.4 | 1,000 
Nov. 17 
The larva (Tables XCVI-XCVIT) .—As is shown in Table XCVI, the 
longevity of larve which hatched in June and were kept in tubes 
under the most favorable conditions was only 71 days. All of the 
larve from eggs of females which dropped in May were dead 2 months 
after hatching. Seed ticks hatching from eggs isolated at daily 
intervals and kept in tubes in the laboratory were frequently found 
to die in 10 days or 2 weeks. The greatest longevity of this stage 
observed by us was between 89 and 117 days. This species, the 
cattle tick, and another species of Dermacentor (albipictus), which 
is now being studied, are the only species occurring in the United 
States, which, so far as known, pass both molts upon the host. As a 
