TEXAS CATTLE FEVER. 1353 



Only a part of the development of the tick takes place on the host ; the 

 rest of the development occurs on the pasture occupied by the host. 



II. Development on the Ground. 



In tracing the life history of the cattle tick it will be convenient to begin 

 with the large, plump, olive-green female tick (fig. 1), somewhat more 

 than half an inch in length, attached to the skin of the host. During 

 the few preceding days she has increased enormously in size as a con- 

 sequence of drawing a Jarge supply of blood. 



When fully engorged she drops to the ground, and at once, especially 

 if the weather is warm, begins to search for a hiding place on moist earth 

 beneath leaves or any other litter which may serve as a protection from 

 the sun and numerous enemies. The female tick may be devoured by birds 

 or destroyed by ants, or may perish as the result of unfavorable conditions, 

 such as low temperature, absence or excess of moisture, and many other 

 conditions ; so that many which fall to the ground are destroyed before they 

 lay eggs. 



Egg laying (see fig. 2) begins during the spring, summer, and fall 

 months in from two to twenty days, and during the winter months in thir- 

 teen to ninety-eight days. The eggs are small, elliptical-shaped bodies, 

 at first of a light amber color, later changing to a dark brown, and are 

 about one-fiftieth of an inch in length. As the eggs are laid they are coated 

 with a sticky secretion which causes them to adhere in clusters and no 

 doubt serves the purj^ose of keeping them from drying out. During egg 

 laying the mother tick gradually shrinks in size and finally is reduced 

 to about one-third or one-fourth her original size. Egg laying is greatly 

 influenced by temperature, being retarded or even arrested by low tem- 

 peratures. It is completed in from four days in the summer to one hun- 

 dred and fifty-one days beginning in the fall. During this time the tick 

 may deposit from a few hundred to more than 5,000 eggs. After egg 

 laying is completed the mother tick has fulfilled her purpose and dies in 

 the course of a few days. 



After a time, ranging from nineteen days in the summer to one hun- 

 dred and eighty-eight days during the fall and winter, the eggs begin to 

 hatch. From each egg issues a small, oval, six-legged larva or seed tick 

 (fig. 3), at first amber colored, later changing to a rich brown. The seed 

 tick, after crawling slowly over and about the shell from which it has 

 emerged, usually remains more or less quiescent for several days, after 

 which it shows great activity, especially if the weather is warm,, and ascends 

 the nearest vegetation, such as grass, or other herbs, and even shrubs. 



Since each female lays an enormous mass of eggs at one spot, thousands 

 of larvae will appear in the course of time at the same place and will ascend 

 the nearby vegetation and collect on the leaves. This instinct of the seed 



