LIFE HISTORY OF NORTH AMERICAN TICKS. 
70 
The life cycles of 15 species and 2 varieties, representing the 
genera Margaropus, Rhipicephalus, Dermacentor, Hemaphysalis, 
Ixodes, and Amblyomma, have been followed and are here considered. 
All molt twice and all but three drop from the host for both molts. 
Dermacentor nitens, Margaropus annulatus, and M. annulatus aus- 
tralis pass both upon the host. One other species, Dermacentor 
albipictus, has also been found by us to pass both molts upon the 
host. Molting closely follows engorgement in species which do not 
leave the host, while with those which drop, a quiescent period of 6 
days or more follows. Some species burrow into the soil to the 
depth of an inch or more to pass the quiescent period and are thus 
afforded protection and drying out is largely prevented. 
As with the Argaside the oviposition, incubation, and molting 
periods vary with the temperature, while the periods of engorge- 
ment upon warm-blooded hosts are but slightly influenced. The 
female usually dies within a few days after oviposition is completed. 
The color of engorged ticks varies considerably, particularly in the 
immature stages; the color may be nearly white, pink, slate-gray, 
or black, dependent upon the comparative amounts of blood, lymph, 
and inflammatory exudate imbibed. i 
Table XIV shows the maximum and minimum periods of engorge- 
ment, molting, and preoviposition in the species studied by us. Owing 
to the fact that the figures for some of the species are based upon a 
small number of observations made at one time of the year, they are 
hardly comparable with others which are chosen from a larger number 
of records made under various temperature conditions. 
Taste XIV.— Marimum and minimum periods of engorgement, molting, preoviposition, 
and incubation of the ixodid ticks treated herein. 
| Larve. | Nymphs. 
Females. 
| Incuba- 
Species. Engorge- Moltine | Engorge- Moltin Engorge-| Preovi- ioe 
| ment | 7o3, e | ment at y a2 ment | position ae e 
period. | PeTOC- | period. | PeT°°: | period. | period. 888 
Days. Days. Days. Days. Days. Days. Days. 
Amblyomma americanum. ..... 3-9 8-26 3-8 13-46 9-24 5-13 23-117 
Amblyommacajennense........ 3-27 10-73 3-13 12-105 7-12 9-20 37-154 
Amblyomma dissimile.......... 4-16 7-16 5-14 12-32 28 6 27-40 
Amblyomma maculatum....... 3-7 7-121 5-11 17-71 14-18 3-9 21-10 
Amblyomma tuberculatum.....|......-.-- 86-165 8-11 29-207 20-25 8-10 91-112 
Dermacentor nitens ............ (4) 8-16 (1) 17-29 2 9-23 3-15 24-394 
Dermacentor occidentalis ....... 2-7 6-12 3-9 13-22 7-10 4-17 21-38 
Dermacentor parumapertus 
MATCINAUS.......----Seee eee 4-14 8-39 4-25 21-123 9-26 5-6 20-24 
Dermacentor variabilis......... 47 7-11 48 6-25 8-16 5-14 24-43 
Dermacentor venustus..........| 2-8 6-19 3-9 11-170 8-17 17 16-36 
Hemaphysalis chordeilis. ..._.. | 5-12 14-92 5-8 26-186 19M, |i. Sea 
Hemaphysalis leporis-palustris . 4-10 18-134 4-8 13-124 17-35 3-15 22-40 
Txodestkingits Shi ces sce +16 27-163 5-66 29-98) || Ske. F 19-65 26-53 
Ixodes scapularis............... 3-9 23-31 3-8 25-26 7+-30+ 15-16 72 
Margaropus annulatus.......... () 5-16 (4) 6-20 25-19 1-66 19-202 
Margaropus annulatus australis. (1) 6-9 | 1 8-13 27-13 1-7 24-34 
Rhipicephalus sanguineus. ..... 3-6 | 6-29 | 4-9 12-29 6-50 3-83 19-142 
1 This species molts on the host; hence the engorgement and molting periods can not be definitely sep- 
arated, and are combined in the molting column, ‘ 
2 These periods include the number of days from the molting of the first nymph to the dropping of the 
first engorged female, and from the molting of the last nymph to the dropping of the last female, 
