12 LIFE HISTORY OF NORTH AMERICAN TICKS. 
perature. Engorgement may take place somewhat sooner when the 
tick is attached at a place where the epidermis is thin and the hypo- 
stome reaches an abundant supply of capillaries than where the epider- 
mis is thicker and a poorer blood supply isfound. Usually ticks attach 
in favorable locations on the host’s body. However, we have found 
Amblyomma tuberculatum to attach to the edge of the carapace of 
the tortoise where the blood supply is exceedingly poor and prob- 
ably insufficient ever to produce engorgement. Few observations 
have been made on the variation in the time required for engorge- 
ment upon cold-blooded animals from that on warm-blooded hosts. 
The few records that we here present, however, are sufficient to show 
that much longer periods are required upon cold-blooded hosts 
even at summer temperatures. On such hosts the parasitic periods 
will undoubtedly be found to vary with the temperature to which 
they are exposed and, as the temperature falls, the difference between 
the parasitic period on warm-blooded and cold-blooded animals will 
probably be found to increase. 
Upon warm-blooded hosts, fertilization appears to be an important 
factor influencing the engorgement of females. While they usually 
engorge quite rapidly after being fertilized, we have observed unfer- 
tilized females to dry up and die while awaiting a mate; others, 
apparently unfertilized, have been observed to engorge, though not 
to repletion, and usually much slower than fertile ones. However, in 
some cases at least, engorgement has been observed to proceed equally 
asrapidly in unfertilized as in fertilized ticks. Definite conclusionscan 
not be drawn inregard to this point until further observations are made. 
Some ticks do not engorge to repletion owing to the formation of scabs 
at the points of attachment, which are sloughed off along with the tick. 
Frequently, being unable to detach from the scab and unable to obtain 
blood, the tick dies attached to the host. Wehave frequently observed 
specimens which were very weak when applied to a host to die shortly 
after attachment. The species of ticks with short hypostomes often 
leave the host as soon as it is killed, but this is not the case with 
those having long hypostomes. Lounsbury (1899) has the following 
to say in regard to this habit: 
Ticks of various kinds have been credited by different people with leaving an 
animal the moment death takes place. My observation does not confirm this state- 
ment. Mr. Roberts shot a badly infested cow while I was at Cottesbrook, and I was 
particular to watch the behavior of the ticks. None but a few fully-engorged blues 
[ Margaropus decoloratus] fell off at first. The pelt was removed and spread out on the 
grass. There were several dozen male tortoise shells [Amblyomma hebreum]and plenty 
of blues and reds [Rhipicephalus evertsi] and a few striped legs [Hyalomma xgyptium] 
present. Many of the males of all four kinds and a small proportion of the females 
detached themselves and wandered about the skin on the second and third days, 
but the majority of all kinds remained attached up to the fourth day, when because 
of the unbearable stench I discontinued my observations. Later it was observed that 
vast numbers of the ticks had dried out without disengaging themselves. 
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