200 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 
eggs 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 : ie 
engorged| Eggs |Hatching raped si eels 
female |deposited.| began. period. aeaal gevity. Maxi- | Mini. | Average | Total 
dropped. : mum. | mum. ay psec 
1908. 1908. 1908. Days. 1908. Days. oi Cir. CRs Se 
ee 22 a 29|} June 5 38 | Aug. 15 71 91 43 73.2 | 1,149.2 
(1 Pes Ieee! (0 ee ane 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 douss<* June 26 32 GOs" 50 96 62 80.3 | 1,195 
ay 2 May A ae 28 3 oe 9 aa Bs ga 80.3 | 1,232.5 
ay 22 ay 2 ObaaSe ug. 28 6 80.3 | 1, 268.2 
May 26} June 2] July 1 30 | Aug. 29 59 96 62 80.5 | 1,124.9 
IN THE LABORATORY. 
2|June 1 3l 87 56 75.2 999 
3 | June 3 32 88 56 75.8 1,049.5 
9} June 5 28 88.5 65 Ti.5 966 
10 | June 6 28 88.5 65 77.8 957 
13} June 8 Poy fig |L es Ses 3 IS eee ae 90 65 78.3 952.8 
14) J ane 9 ef en Sel | ee 90 e 78.7 963.3 
15h peeaOness Gy Sowa se ee oo ee 90 7 79 935.3 
31} Before Less than 30): -Dec:5s) About 98-52. -7<..|5 sss —e en oe ae oe Eee 
Aug. 29 
2,|...d0..2. -| Lessihan'28' |) Nov. 260) Aihowt)89)| 52. -2.2252 | aoe asec |o seca te | See 
6 | Aug. 2 24] Nov. 26-| 89-117 99 73 85.25 | 1,014 
Dee. 24 
9} Sept. 1 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 
Jarve 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 
