SUMMARY OF LIFE HISTORY. 19 
SUMMARY OF LIFE HISTORY OF THE SPOTTED-FEVER TICK. 
As is the case with nearly all species of ticks, this one passes 
through four distinct stages, namely, the egg, the larva or seed tick, 
the nymph, and the adult. « 
THE EGG AND LARVA. 
The eggs (PI. II, fig. 5) are small, ovoid, brownish objects, about 
one thirty-eighth of an inch long. These hatch into minute, light 
brown, active six-legged creatures known as larve or seed ticks. 
(Pl. III, fig. 2.) Before further development takes place it is neces- 
sary for these seed ticks to feed upon the blood of some animal. 
They usually attach to small mammals, such as ground squirrels, and 
become filled with blood in from 3 to 8 days. They then drop off the 
host and find a convenient protected place in which to continue their 
development. Before engerging the seed tick measures about one 
thirty-seventh of an inch in length, but during feeding the body is 
considerably distended, so that it measures about one-eighteenth of 
an inch in length by one thirty-first of an inch in width when en- 
gorgement is complete. The color of the larve when engorged is 
slate-gray. Activity is greatly reduced on account of the weight of 
the blood imbibed. 
THE NYMPH. 
a 
After a resting period cf from 6 to 21 days the skin is shed from 
the body of the engorged seed tick and an active eight-legged nymph 
appears. The extra pair of legs is gained during the resting stage. 
This character is sufficient to distinguish the nymphs from the pre- 
ceding or larval stage. In this stage it is necessary for the young 
tick again to find a host and fill with blood. This feeding period 
requires from 3 to 9 days. When engorgement is complete (see PI. 
II, figs. 3, 4), the nymphs measure about one-sixth of an inch in 
length, while before engorgement the length is usually about one- 
seventeenth of an inch. The engorged nymphs are bluish gray in 
color and not very active. : 
THE ADULT. 
As in the case of the engorged larvee, the nymphs, after dropping, 
seek a protected place in which to transform, and there become com- 
pletely inactive. This resting stage requires a longer period than 
the preceding. During this time the sexual organs of the ticks de- 
velop. When the skins are shed the ticks appear as mature males 
and females. Shortly before the molting of the nymphs the lght- 
colored shields on the back of the adult ticks can be seen through 
the thin skins which are soon to be shed. After the mature ticks es- 
cape from the nymphal skins they are rather soft and comparatively 
