74. LIFE HISTORY OF NORTH AMERICAN TICKS. 
THE LARVA. 
Upon hatching, the larve of many species remain clustered to- 
gether for several days near the eggshells. Finally they crawl upon 
nearby herbage, such as grass, weeds, and even small trees, posts, 
or buildings, and there await the passing of a host. Some ticks, 
such as the species commonly found on dogs and rabbits, drop near 
the kennels or sleeping places of the hosts, and when the larve are 
ready to attach they may crawl about in search of the host. 
Having once found a host the larve cling with great tenacity, 
crawling about over the body until a suitable place for attachment 
is found. The position of attachment upon the host varies with 
the species. Attachment may take place at once, or the tick may 
wander about for several days before attaching. This delay in attach- 
ment, the quantity and quality of the ingesta obtained by different 
specimens, and individual vitality account, in part at least, for the 
variation of from 2 to 14 days in the period between the applica- 
tion to hosts and the dropping of engorged larvee from warm-blooded 
hosts and of from 10 to 18 days in the case of cold-blooded animals. 
After dropping, engorged larvee usually remain active for only a few 
days before becoming quiescent, durmg which time they crawl to 
some protective covering. In some species, however, a considerable 
period is passed before the engorged larvee become quiescent. From 
10 days to several weeks may be required for the metamorphosis of 
the larva. This quiescent period varies primarily with the species, 
the temperature, and the humidity, the first two being the more 
important. 
THE NYMPH. 
In general the longevity of the nymphs is somewhat greater than 
that of the larve. In awaiting the hosts, their habits are very 
similar to those of the larve. In those species which molt upon 
the host, the adults crawl from the nymphal exuvia and reattach 
nearby. The periods of engorgement are quite similar to those of 
the larvee, but the quiescent periods are somewhat longer. 
There is considerable variation in the size of the engorged nymphs. 
The smaller ones usually become males and the larger become females. 
In the species with color markings on the scutum, as in the species 
of Amblyomma, the markings can be seen through the skin that is 
about to be shed. The sex can thus be determined from one to 
several days before the molt takes place. Following engorgement, 
if passed upon the host, molting takes place after a very short quies- 
cent period. With the species which drop for the nymphal molt, 
from 1 day to as much as 6 months of activity are passed prior to 
the quiescent period. During this period of activity the nymphs 
attempt to find some protected.place in which to transform. Par- 
