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. 
TasLeE XCI.—Engorgement of larvxe of Dermacentor variabilis. 
Larvee dropped engorged—days following 
application. Total 
Date larve applied. Host. number 
dropped. 
PalyiS) WOOT a2 smaann a Bovine... - 0 0 0 3 3 0 0 6 
Aa. GO yates oh eet Sudorsk 42 ) 0 Oia e3Tbll ok27 2 0 66 
wurne)5; L908 s= 2-2). y= 2d022.<-=- 0 0 0 5 17 24 3 49 
0 0 0 0 0 5 0 5 
RTL 0 a ae as Nee a Os oO eea see 
Molting occurred in August as soon as the seventh day after drop- 
ping. Ata mean temperature of 81° F. molting took place in 8 days, 
during which time a total of 306° F. of effective temperature 
accumulated. 
TasBLe XCII.— Molting of engorged larve of Dermacentor variabilis. 
Engorged larvee molted— Temperature from 
days following drop- dropping to date first 
ping. tick molted. 
Total 
Date engorged larvee dropped.| Host. hee 
Aver- 
molted. Maxi- Mini- age 
ee 
oO 
a 2 
5 Bp Bo AO pth 2 mum. | mum. | daily 
mean. 
v4 
ae PRE be 
Aiea 1007 5-2-3202 coc ee :...-| Bovine SOP TOA ple La este) SO 3 25..9208 | oO Sale eee 
aie 95: W007 s25,. 25 5558-38 OSs Oey a) Oe OG Bil. uczalic ae eee 
TREE AC 1 ty Peas ae ae ae Ae peidoesee Se Sa S| alll OL. © ry (RR [ES ARR NESS - 
HAUTE US OF Gone seer eaae BSEC OBER onl 4 | kel ale outa) 20) ZAP | cra cela stele [ernie cers Cement 
RGD bel G0 sen -accee cia aeinciele Dog HH O79 \ OP PORNO | 051710 hi Peeper Mer sem casos 
WIN COS AGUS. coe wclnnsniwiesists won i COO CO ey |p ON) 4 91.5 69 79. 87 
June 10, 1908 Re eee | (Gl ree OJ fit mc wach 16 91.5 69 80. 50 
June 11, 1908 OG| mesial wiin| heron eel) nO 14 91.5 70 81.19 
June 12, 1908 sate 0 2 0; 0 0 0 2 91.5 71.5 81.39 
Alig 324,908 «seis Sooo oes SoEOO eee SP On) “Onl 2) a2 a 5 90 75.5 83. 27 
Motel 195 [oe tie oa eee 100 | als PEST 
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. 
