DEVELOPMENT OF THE IXODIDA. 71 
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 larve of this species exhibit 
great longevity. Moisture is one of the most important factors in 
determining the longevity of ticks. After larvee 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 larve; 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 
observed. 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 Izxodidz. 
Larva. Nymph. Adult. 
Species. | 
Summer.| Winter. |Summer.|} Winter. |Summer., Winter. 
Days Days. Days. Days. Days Days. 
Amblyomma americanum,....-....-.---- 1150 2297 476 476 | 393-43 393-430 
Amblyomma cajennense.........---.----- 2 386 2 386 408 408 466 466 
Amblyomma dissimile...................- he eco ee Re Pei Fa See 129 103 
Amblyomma maculatum...............-. 2107 £2 SOROS eae ae | 388-411 388-411 
Amblyomma tuberculatum..............-|........-- 1 95-110 Sh ee eee hb Beemer es 2 
BeerInaePTILO’ MICOS... <2. 22 eee nee Po EE ify BARES EE) SL Cer REE eee ae ae ee a 
Dermacentor occidentalis..............-.-- 2 105-124 281 69 76-108 243+ 2438+ 
Dermacentor parumapertus marginatus. -. 1 297 27 ip eS KOR ge SO) eee S 
Dermacentor variabilis........-.....-..-- 2 335 2335 | 200-216] 200-216 202 233 
Dermacentor venustus...............-.-.- hi Silla aan 185 | 252-271 413+ 413+ 
Hecemaphysalis chordeilis................-. oe feo eee eal ee eee 74+ 305 305 
Hemaphysalis leporis-palustris........... 2 258 2217 342 342 588 588 
ONS See oe 6 RE ee ee 2209} 2215+ }.......... 68-171 1 Ba eey ss 
ee a ce Sh Be ees 75+ POSS Wee a ae Ae ee ee I RECS aE 
Marparopus annulatus.........-...-.....- 2125 i UC i 4 Seek eee! Wee Ae CO pe eed Dee at «3 
Margaropus annulatus australis..........- Boe Bae yl Pe aS Oe Ss ee Cae = 
. Rhipicephalus sanguineus..............-- 280 | 2131-138 75 183 158 214 
} Record based upon larve hatched from eggs deposited on 1 or 2days. Longevity computed from begin- 
ning of hatching to death of last larva. 
2 Record based upon larve 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- 
