DEVELOPMENT OF THE IXODIDE, cei 
LONGEVITY. 
The period of life of the free ticks while awaiting a host is of particular 
importance economically. In general the larve of the species which 
pass their molts upon the host appear to be shorter lived than those 
of other ixodid ticks. Dermacentor albipictus, which molts upon the 
host, is an exception, however, as the larvee of this species exhibit 
great longevity. Moisture is one of the most important factors in 
determining the longevity of ticks. After larve become weakened 
by fasting, a damp period has been observed to furnish conditions 
favorable to the development of various fungi upon them and to result 
in the destruction of large numbers. However, a certain amount 
of moisture is essential. The absence of moisture, especially during 
hot weather, is even more destructive than an excessive amount. 
The free nymphs are usually longer lived than the larvee; in a number 
of species they have been found to live as long as the adults. Accord- 
ing to Dixon (1910, p. 26) Lounsbury has found adults of Rhipicephalus 
evertsi to be alive, when kept in bottles, after a period of 18 months. 
Table XV summarizes our data on the longevity of the species 
observéd. These records can not be considered as falling exactly into 
either of the two seasonal divisions used, as some were made during the 
spring and fall and others include part of summer and part of winter. 
TaBLE XV.— Maximum longevity recorded for species of Ixodide. 
Larva. Nymph. Adult. 
Species. 
Summer.| Winter. |Summer.| Winter. |Summer.|} Winter. 
Days. Days. Days. Days. Days. Days. 
Amblyomma americanum,....-.....----- 1150 2297 476 476 | 393-430 393-430 
Amblyomma cajennense...-..------------ 2 386 2386 408 408 466 466 
Amblyomma Gissimile’. cco. sss cle ei Oe al Meee eee 1 101 eects 129 103 
Amblyomma maculatum......---....---- 2107 3 LFA) |= sae eR] CERT 888-411 388-411 
Amplyomms tiberculatumss.2-.c2ecss--|--cce-e eee 1 95-110 ‘US | awe eae tT RARE sasc 
Dermacentor mitens ja. x55 ceca... 2,-c ste -seee Ra aU i ate Babee SOme GeRere) GE ee nen lESereR eee Se oeoee aac 
Dermacentor occidentalis............----- 2 105-124 281 69 76-108 243-+- 243-+- 
Dermacentor parumapertus marginatus. -- 1227 WOT loaneonk ae LS lo l5S le cee 
DERMIACEHTOL VATIADINS \e'lsace o2ee ees e ee 2 335 2335 | 200-216 | 200-216 202 233 
Dermacentor venustus.................... CIN |e eee ees 185 | 252-271 413+ 413+ 
iHemaphysalis) chordeilis: 5. 22 22ee 2-52 9305 ett ceeeces| teas sce oe 74+ 305 305 
Hemaphysalis leporis-palustris....-...... 2258 2217 342 342 588 588 
ESO CLES MCI De reenter amc cet 2 209 VONS-l ee eweee eke 68-171 1O4As Ce Dee ee 
ES OGeSISCAPINATISE n Sueeee ~ sates oes (eee cise 75+ GOA=al Sot ae close eames aotearoa 
MarParopus annUlatuSs occ 2 << e anne 2125 Bi DTN ee eee ere | es ce eS ere eta ies ee 
Margaropus annulatus australis........... VA Ee EIS) CSO on] Reese sea Heme riceae Soren or 
Rhipicephalus sanguineus................ 280 | 2131-138 75 183 158 214 
1 Record based upon larve hatched from eggs ee onlor2days. Longevity computed from begin- 
ning of hatching to death of last larva. 
2 Record based upon larvze hatched from all eggs deposited by a female. Longevity computed from 
beginning of hatching to death of last larva. : 
PARASITIC PERIOD. 
There are a number of factors that influence, more or less, the para- 
sitic periods of the ixodid ticks. Among these are the point of attach- 
ment to the host, fertilization, inability to detach, body temperature of 
the host, and, especially on cold-blooded hosts, the atmospheric tem- 
