172 LIFE HISTORY OF NORTH AMERICAN TICKS. 
The nymph (Tables LXXIX-LXXX).—The greatest nymphal 
longevity observed by us occurred in the case of a lot of 119 nymphs | 
which molted from larvee September 5-10, 1909. These nymphs, as 
also all other lots here recorded, were kept in the laboratory in tubes 
on moist sand. During the fall months 21 nymphs were removed 
from this lot and put on hosts, and during March, 1910, 16 were 
applied to hosts, 10 of these being applied March 18. On April 20, 
1910, only one specimen was alive. This individual died before 
June 3, 1910. Thus it is seen that during the winter months a con- 
siderable number of nymphs lived for at least 189 days, at which 
time they were applied to a host and became engorged, and one 
nymph lived between 252 and 271 days. It seems certain that had 
none of this lot been put on hosts, some individuals would have 
lived considerably longer.t In alot of 12 or more nymphs which 
molted from larve April 19-21, 1908, 3 individuals were alive 178 
days later. The last specimen died October 21, 1908, having lived 
between 183 and 185 days. One individual in a lot of 7 or more 
specimens which became nymphs July 24-25, 1908, lived between 
137 and 145 days. All specimens in two other lots of about 7 indi- 
viduals each were found to have died between 56 and 75 days after 
they transformed to nymphs on July 25, 1908. 
Among nymphs which were collected from hosts when slightly to 
one-third engorged, a longevity of from 47 to 122 days was recorded. 
The longest period—namely, 122 days—was observed in the case 
of one individual in a lot of 59 unengorged or very slightly engorged 
nymphs which were collected on a ground squirrel on April 12, 1910, 
at Florence, Mont., by Mr. W. V. King. 
Nymphs kept in tubes in the laboratory at Dallas were found to 
be active most of the time at all seasons of the year while awaiting 
hosts. Occasionally a few individuals were seen to be grouped 
together and remaining quiet. These, however, were readily dis- 
turbed. 
In most instances nymphs have been found to attach almost 
immediately after being placed on a host. Individuals have been 
found to attach to a host and become engorged after having been 
picked from another host when as much as one-fourth engorged. 
Engorged nymphs have dropped as soon as the fourth day following 
attachment, the last leaving the host on the ninth day. This period 
is the same as that recorded by Ricketts (1908, p. 101). The en- 
gorgement period of nymphs which were collected on hosts when 
slightly engorged appears to be somewhat shorter than in the case of 
those nymphs which have not before been attached to a host. In 
two instances these slightly engorged nymphs have been found to 
1 Since the above was written a record of nymphs living over 300 days has been made by us. 
