THE BROWN DOG TICK. 107 
TaBLE XXXIII.—Engorgement of larve of Rhipicephalus sanguineus. 
Larve dropped engorged—days following application. 
Date larve applied. Host. SQ a] ee 
Oct. Sw1907escct~ tenons Boviie.s-: 0 
0} 51] 138 6 2 0 0 0 197 
Mavi 1908-0500) 6. 4.-|.<< 00.0... 0 0 Ou) 5811.48 2 0 0 0 78 
June/6, 1908.......-..... yay: eae 0 0} 25] 85] 31 0 0 0 0 141 
At a mean temperature of 82° F. larvee which dropped engorged on 
June 18, 1908, commenced to molt on the sixth day, while ticks which 
dropped October 6-8 did not commence to molt until the twentieth and 
twenty-third days. An effective temperature of 235° F. was required. 
Christophers states that 9 or 10 days are required for molting. 
The nymph (Tables XXXIV, XXXV).—In order to determine the 
longevity of nymphs, a large number which molted September 30 
and 31, 1907, were kept in a tube in the laboratory on moist sand. 
On March 5, 1908, 12 were alive, while on March 28 only one survived. 
On April 1 the remaining tick was found to be dead. Thus all of this 
lot were dead in 6 months from molting. Four of 6 nymphs which 
molted June 8 and 9, 1908, were dead August 3; on August 10-one 
was still alive, but on August 20 the last one was dead. Thus in 
summer nymphs lived but two and one-half months at the longest. 
Of a lot of 23 nymphs, slightly to one-third engorged, that were 
collected on dogs, October 29, 1910, 2 lived until April 5, 1911, or 
158 days. 
Engorgement was found to take place as soon as 4 days after attach- 
ment. The greatest number dropped on the fifth and sixth days; all 
were engorged and had left the host by the tenth day. 
TABLE XXXIV.—Engorgement of nymphs of Rhipicephalus sanguineus. 
Nymphs dropped engorged—days following application. 
Total 
ota Host. number 
lie (nde hl l= Il wg Vl Wh ala | 10 | dropped. 
Wowenn etOOT see. cc Bovine.... 0 0 0 3 10 2 0 1 0 0 16 
auilyels e008. == —.|0 --dO.2 -..5..,- 0 0 0 3 10 15 5 5 1 0 39 
In summer, when the mean temperature was between 84.65° F. 
and 85.42° F., molting has been observed to take place as soon as the 
twelfth day. A total effective temperature of 500° F. is required to 
produce this molt. The molting period of nymphs which form males 
appears to be the same as for those which form females. Christophers 
found 15 days to be required for molting. 
