j MATING AND FECUNDATION. 29 
becoming engorged appears to be an adaptation for protection and 
to provide moisture for molting. 
The clustering of the larve undoubtedly decreases the rapidity of 
drying out and thus increases the longevity of that stage. The 
larvee of Dermacenter albipictus, a species which is now being studied, 
remain in dense clusters for months on the sand in tubes without 
making any effort to find a host. This seems to be a protective habit 
developed in order to pass the time between generations. 
The engorged females of most of our species have a habit of find- 
ing protection as soon after dropping as possible in order that they 
may deposit their eggs unmolested. 
MATING AND FECUNDATION. 
Fertilization may take place during attachment or after the females 
have engorged and left the host. Several instances have been reported 
in which mating has taken place before attachment to a host, but 
whether such unions result in fertilization has not been determined. 
Thus E. G. Wheler (1899, p. 632) collected unengorged specimens 
of Ixodes ricinus on herbage which mated when kept in confinement. 
He also observed mating of a male and an engorged female taken 
from a deer. 
Mr. J. D. Mitchell, as reported by Hunter and Hooker (1907), 
observed a pair of Amblyomma americanum clinging to herbage with 
the mouthparts of the male inserted in the genital orifice of the 
female, and Mr. C. W. Howard (1909) reports a similar observa- 
tion in the case of Rhipicephalus ecinctus. 
Dr. H. T. Ricketts (1909, p. 99) states that with Dermacentor 
venustus fertilization will take place even when the ticks are not on 
an animal host. Just what he intended to convey is not clear, but 
it would appear that he meant that copulation took place away 
from the host, probably after removal. The writers have observed 
this habit in Jzodes scapularis, both upon and off the host. An 
unengorged, unattached female taken in the field from a hunting 
dog and placed in a pill box with unattached males taken from the 
same dog was shortly after found in this relation with one of the 
males. These observations do not prove, however, that fertiliza- 
tion follows such unions, and investigations may show that the 
engorgement of blood by one or both sexes is necessary. 
With the Argaside fertilization takes place after the adults have 
engorged and left the host. Thus the nymphs of Ornithodoros 
megnint leave the host, molt, and without further feeding are fer- 
tilized and commence oviposition. Prof. Lounsbury states (1903a, 
p. 268) that in Argas miniatus mating takes place a few days 
after engorgement. He says that the male inserts the rostrum into 
