194 LIFE HISTORY OF NORTH AMERICAN TICKS. 
seen in the table, the longevity of the different lots varies greatly. 
We have not been able to account satisfactorily for the large differ- 
ences in lots kept under similar conditions. 
The shortest time in which engorgement took place was 4 days, 
the greatest number dropping from the host on the fourth to sixth 
days, while the last to leave the host dropped on the seventh day. 
TaBLeE XCI.—Engorgement of larve of Dermacentor variabilis. 
Larve dropped engorged—days following 
application. Total 
Date larve applied. Host. number 
dropped. 
DULY pol AGO oe seek ee ee cee ea eee Boyine.... 
0 0 0 3 3 0 0 6 
Aug. 5; 19076 seates. See ace eGEke J4 GOse2 ve 0 0 0 37 27 2% 0 66 
TUNE 5-1 GUSH aes cede se ome er ae eed Onssase 0 0 0} 5 17 24 3 49 
pA gS 1908 Me eel cccee me soceseeee & 2 GO yaaa 0 0 0 0 0 5 0 5 
Molting occurred in August as soon as the seventh day after drop- 
ping. At amean temperature of 81° F. molting took place in 8 days, 
during which time a total of 306° F. of effective temperature 
accumulated. 
TaBLeE XCIT.— Molting of engorged larvx of Dermacentor variabilis. 
Engorged larve molted— Temperature from 
days following drop- dropping ns date first 
ing. ¢ 
ping Total tick molte 
Date engorged larvee dropped.| Host. : | Bee 
B molted : |) EVER 
5 F mum. | mum. | daily 
mean. 
a 
pe ae ii oO 
At pVA MOOT Ss cto see = dee Somes Bovines.|) (3) (ONO As aie) IO 2 dl Ree ae Meee solo occ ac 
Wags '5, 1907S. Se Reale dOno=s Se Oa 2a, ACTON MOR Stii.i..colls 2 eee | ee 
TE 17 le en ee wi do: 87 |. 9) 1821 te) OLE sou 8 OR |e!) en 
AE. LOO fcc cao aso ce reel ooe d02..2. 20. |) Aalde eeeelsnte clatter 2a lien nee n|tson eee acer 
Sept WOO wes tennessee Dogs see ARs OF MOA MOS O4). a0 0 floor See 
Jurie'9;, 908 64. en 2 science Bovine:-| cov) O00) 925) 20) S00 4 91.5 69 79. 87 
SUNT OIGOSE eee ea ee ene dors--- TST ON On Sel ras ea 16 91.5 69 80. 50 
June G082 ce aa es - Se seal oe doses. ZAM HOR 23a) eee oul ya vata 14 91.5 70 81.19 
June d2: 1908= 3. 4-32 -oe--e 5c Orne. 33) Ol sa} MOM Only (One 2 91.5 71.5 81.39 
Agi 2419085 pe see sae ceee se elec do=2te- Be oe On| el ON || eae erect 5 90 75.5 83. 27 
Motal’ one edie os 100 | ie MD ra 
The nymph (Tables XCIII-XCIV):—A number of nymphs which 
molted on August 18, 1907, were alive March 5, 1908, but dead on 
March 21, 1908, the longevity of this lot being from 7 to 8 months. 
In another instance, however, nymphs which molted on June 18, 
1908, were dead on August 4 of that year, and the last individuals 
of a third lot, which molted September 9, 1908, died between October 
16 and October 26 of the same year. All of these lots were kept on 
moist sand in the laboratory. 
