THE ROCKY MOUNTAIN SPOTTED-FEVER TICK. VL 
the thirteenth and sixteenth days; when the mean temperature was 
about 77° F. molting began between the efghth 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. 
rd Temperature 
Engorged larvee molted—days following 2 | from dropping 
dropping. xe) to date first 
Date Fs) tick molted. 
engorged 5 
larve Host. = : Sifonss 
dropped. as 5 g 5 aoe 
o , =r. 
[6/7] 8] 9 [10/11 )12/ 13 | 14) 15] 16 | 17/18) 19 a Ble |e a8 
5 $|8 |8/e08 
A SP iret ess 
1908. ie pal eee ks 
Ars 4.) OVINE: <}.\sai- <i <i-ia' 3] 0} O} OF OF OF OF OF OF OF OF 1] 1) OF O 2) 85 [54 70 
L273) peal Jal RSA (aera recat 23} 0) O;| O| OF OF OF OF OF OF 2) 2 7 2 1) 14/85 I58 70.5 
pte Olio Cs EOE ees eme 27) 0} OF OF OF OF OF OF 1) 5} 11) 6] 2) OF OF 25) 85 J58 70.4 
AMDT talleanes GOmeae seeees 17} 0; OF OF OF O OF OF LT] 7% 2 2 2) Ly OF 615) 85 [58 70.3 
Apres (Saitek. 2 GOs ese 13] 0} O; O} O| OF OF OF OF 5] 8} OF O} OF O} 13) 80 58 70.3 
May 17012. -.-2 Geen sane rs 15} O} O; OF OF 1) 9] 2 1} OF OF OF OF OF] OF 613) 87 6g 77.4 
May 18 |..... 0 kt eS Ae 10} 0} O} OF 1) 6 3) OF OF OF OF OF OF OF OF 610) 87 [6s 77.6 
duly, 15) |.5--: GOS ests siec ees 76; Oj} O} O} 2 26] 31) Of] O}| OF OF} O} OF OF O} 659) 95 176.5) 84.3 
July 16 Fdo: Sse -25-3 = 43) 0} O} 4/17) 20) 2) 0} O} O} OF OF OF} O} O} 43) 95 176.5] 84.4 
duly 27 2-32. OWS anns are wees 9g) O} OF O} 5} -1) 1} OF OF OF OF OF OF O} O 7| 95 {76 83.9 
1909. 
duly, 19). 225. doe s< eet oe Site Ub) Zap Os dS oA Peele a5) [se] Eccl oodl hae ace| bee 3] 97 179.5) 89.72 
Aug. 2] Guinea pig.....-..- GO en UO} th SO On OOo Ole ales. 6/102 |78.5) 88.57 
Aes) (Oils cera Oiisaes o1- 5 33 mipeOne ale] OUTIL ole ese ere cies oaeete as 96 |78 85.75 
(ATI. 292: GObe acct eeeed 36} 0} ()} 22) 5} 5} 1) OF O} O} OF OF OF O} O} 633) 98 {80 88.5 
Aug. 30 }..... GOse eens Fences 49] (1)} 8] 21) 7} 2) O} O} OF OF OF OF OF OF O} 38] 98 Iso 88.37 
Aug. 31 }..... GO soscce sieaee 60} 0} 10} 30) 12) 0} O} 0} OF OF OF OF O} OF O} 652) 98 78.5) 8s.1s 
Septaedy |. 2522 OG) 255. eet eh = 56) 2) 14) 27; 5] Of 0} O; O} OF OF OF OF} OF OF 48) 98 I78.5) 88.29 
Do RAD DIG ao se 2a 2) O| 1) O} OF OF -O} OF OF OF OF OF OF OF O 1) 98 |78.5} 88.32 
Sept. 2] Guinea pig........ 25) 0} 12; 8) Of OF O}| OF OF OF OF OF O O} O| 20) 99 I78.5) 88.55 
1910. 
July 42) Ground squirrel...| 17] 0) 0} 0} ©} O} 1] 0} Oj 06} 12) Oo} 1] Of O| 14] 97 I73 85.5 
July 142)..... On cee ELES-E 23) 0) 0} O} O} O} 17) 0} 3) OF OF} OF OF OF} OF = 20/103.5)73 88. 25 
July 222) Chipmunk........ 20; 0} O| O}| OF OF OF 17; OF OF OF OF Of OF OF 17/104 Js0 90.5 
July 292) Ground squirrel...| 14] 0) 0} 0} 0} ©} O| 0} 6] 2) 6...]...]...]...| 14/104 179 84. 48 
Aug. 102) Pine squirrel...... 2a Ol Ol, Ol Ot iG) | ea sees 5 ASee Gee Gee 19/104. 5/82 92.1 
Aug. 142) Woodrat......... 3} 0} O} 0} Of O| O TY 8) aT 3/104. 5/73 90. 69 
TOUS sews se 586]. ..]...]--- B96) Seas sl! Sale ee ae 
1 The larve which molted on this day are included with those recorded on the following day. 
? These ticks were picked from native hosts in Montana and varied from one-half to fully engorged. 
