THE ROCKY MOUNTAIN SPOTTED-FEVER TICK. 171 
the thirteenth and sixteenth days; when the mean temperature was 
about 77° F. molting began between the eighth and tenth days, 
and when the temperature was about 88° F. molting began between 
the sixth and eighth days. Cooley reports (1909, p. 101) that larve 
which dropped during the latter part of July at indoor temperature 
at Bozeman, Mont., commenced to molt in as soon as 13 days there- 
after, and that the majority molted within three weeks. We have 
found that larve will often molt if removed from the host when 
only slightly over one-half engorged. The molting period of speci- 
mens which are not fully engorged is noticeably longer than in 
replete individuals. | 
The last six lots, the molting of which is recorded in the accompany- 
ing table, contained. individuals from one-half to almost fully 
engorged. The length of the molting period was undoubtedly 
lengthened on account of the ticks having been picked from hosts 
before they were replete. The temperatures given with these lots 
are those recorded at the Dallas laboratory from the time the ticks 
were collected in Montana until molting began. The specimens 
undoubtedly experienced lower temperatures than those recorded 
during the few days prior to their receipt at Dallas. 
TaBLeE LXXVIII.— Molting of engorged larvx of Dermacentor venustus. 
3 Temperature 
Engorged larve molted—days following & | from dropping 
dropping. : ir) to date first 
Date = tick molted. 
engorged 5 
larve Hast. a = is >| On 
dropped. = ! 31/8 /8/% 
2 “4 | 3 ¢ S sisic=s 
@ | 6] 7] 8/9 | 10/11) 12/13/14) 15/16)17/18/19] - | £ | B sag 
5 | a OM Die ee 
Z | = 3 = ee = 
a E a |lai< 
1908. | | 2. | °F. 
ee 2 3} 0} O} O}| 0} OF O 00 OF 1) 1 O 0} 2) 85 70 
mor. 66 |. .... Deans gatinds «5 0} Oo} OF OF} 0} O oO} 0} 2 2] 7 2 1) 614) 85 70.5 
pes 6.)..... ee ee 27; 0} O} OF OF OF O 1; 5) 11) 6 2 OF O} 25) 85 70.4 
iy Sak 2 Sa Se ee 17} 0} O} OF OF OF O 1 7 m2 2 ty O| 15) 8 70.3 
iv" se? oe ORG te ha Pat 13} 0} O} O} OF OF O oO} 5) 8} OF OF OF 0} 13) gO 70.3 
May 17|..... ae ee 15} O} OF OF} OF 1) 9 1) oO} OF OF OF OF OF 13) 87 77.4 
May 18 |..... i ee oe Sen 10} O} OF} OF 1) 6 3 0} O} OF OF OF} OF O} 10) 87 77.6 
July 15 |..... ie cee a3 76} O} O} OF 2) 26) 31 0} O} O} OF OF O} O| 659) 95 [76.5) 84.3 
July 16|..... ee oat 43| O| 0} 4| 17] 20} 2 0} O| Of 0} O Of OF 43195 |76.5| 84.4 
ge es _ eee 9) Oo} OF OF 5) 1) 1 0} oO} OF OF O OF O 7| 95 83.9 
1909. 
eee 9. 6e NOS os -s - - ee 2 TE Se es Se ee ee ee es 3} 97 5) 89.7 
Aug. 2 | Guinea pig........ Oo} 1; 1] 2 OF 1 a OO Oe <2 6,102 5) 88.57 
pe ee ee a A a SE ee ee ee ee ee 7) 96 85.75 
Aug. 29 ]..... ag eee PEE: 0} (2)} 22} 5) 5) 1 0} 0} OF OF O OF OF 33) 98 88.5 
Aug. 30 ]..... a eee (})} 8} 21) 7) 2] 0 0} Oo} 0} OF OF} OF} OF) 688) 98 88.37 
Aug. 31 |..... eS eee 0} 10} 30) 12} oO} O 0} O} OF} 0} O OF O} 52) 98 78.5) 88.18 
Sept. 1 }..... ag, SS tse 2) 14) 27; 5) O} O 0} OF} OF} Of} O OF OO 48) 98 -5| 88.29 
ee 5 a 0} 1] 0} O| oO} O 0} O} 0} 0} O OF O} 1) 98 J78.5) 88.32 
Sept. 2 | Guinea pig........ 0} 12; 8} OF OF O oO} Oo} OF 0 0} O} 20) 99 .5 88.55 
1910. 
July 42 Ground squirrel. .. o| 0 0 Of O} 1 0} 0} 12) 0 0 
OS eT, Sarees 0} 0} O OF O17] OF 3} OF OF O 0} 0 
July 222) Chipmunk........ o| 0 0 Of O 017] 0 | o Oo 0} 0 
July 292%) Ground squirrel... o} 0) OF OF OF OF OF 6G 62 6.-../.. aa 
Aug. 102) Pine squirrel...... Oo} 0} OF OF 7] @)} 11) 1)-..]-...].. 
Aug. 142) Woodrat......... Oo} Oo} O OF} OF} O} 1) 1) O 1. 
Ne SS SS eee ee 
— 
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1 The larve which molted on this day are included with those recorded on the following day. 
2 These ticks were picked from native hosts in Montana and varied from one-half to fully engorged. 
