398 



BUREAU OF ANIMAL INDUSTRY. 



bered the same as the legs, coxae I to IV, tarsi I to IV, etc., meaning 

 the coxae or tarsi of the first, second, third, or fourth pair of legSj 

 respectively. 



THE LIFE HISTORY OF TICKS. 



Ticks are temporary parasites, attacking mammals, birds, and rep- 

 tiles. They do not appear to be so strictly confined to certain hosts as 

 do parasites in general. Still, this may be more of an apparent than 

 a real rule. Certain it is that, although a given tick may be found 

 occasionally on animals which are very dissimilar (dog ticks have, for 

 instance, been found on snakes), still the various species show a 

 decided predilection for certain hosts. 



The parasites copulate during the period of parasitism, and suck the 

 blood from their hosts. The female grows to a large size and eventu- 

 ally drops to the ground and lays numerous eggs, which are usually 

 more or less clustered together. The larva upon hatching possesses 

 three pairs of legs, the fourth pair being added during a molt. Either 

 the hexapod or the octopod form may attack its host. 



In case of the Texas fever tick the details of the moltings have been 

 established by Curtice (1892, pp. 238, 239-241) as follows: 



The following table will serve to illustrate the sequence of events in the experi- 

 ment and present it in rough but compact form: 



Date. 



Stage of experiment. 



Time consumed in various stages. 



1889. 







Oct. 3 







Oct. 10 



Egg laying finished 



Ovipositing one week. 



Nov. 4 



Ticks appeared 



Hatching, three and four weeks. 



Nov. 15 



Bearing begun 



Unnecessary interval of one week. 



Nov. 22 



First molt, larva to nymph 



Larval stage lasted one week. 



Nov. 29 



Second molt, nymph to adult 



Lasted one week. 



Dec. 11 



Female half grown with male 



About two weeks later. 



Dec. 16 



Experiment closed 



About one week. 





Experiment endured 



About two and one-half months. 



Having briefly reviewed the experiment we may now study its products. 

 The eggs were laid in a little mass; were subovid, dark brown and opaque, and 

 coated with some protective substance. In alcohol they show a thin shell-like cov- 

 ering with a dark opaque mass within. In the latter stages of incubation the form 

 of the young ticks became more and more apparent until they emerged. The exit 

 from the shell seemed to be by the shell rupturing and the imprisoned occupant 

 / thrusting it off with its feet. The torn edges afterward rolled inward and produced 

 the appearance of clam shells, so frequently mentioned in writings on this subject. 

 * ^ ^ -x- * ^fr * 



The young ticks, or larvae, when they emerge are whitish, they gradually turn to 

 chestnut brown and resemble minute seeds. Though I have never seen the seed 

 ticks of the South since I have begun to study them from a standpoint other than to 

 rid myself of them, I think that the young of the cattle tick may form a large portion 

 of them. 



The date of the first collection, November 22, was a week from the time the young 

 ticks were put on the calf, and very fortunately coincided with the time of the first 



