THE ACARIXA OK MITES. 



59 



Fig. 109.— Shield of -l/ar- 

 garopus annulatus, 

 (Original.) 



female. 



them have been showu to transmit the germs of some disease, so that they become, in 



many cases, economic pests of prime importance. The losses caused by ticks are of 



enormous extent. The damage done by the cattle tick follows 



not only from the transmission of disease, but sometimes also 



from the loss of blood caused by heavy infestation and greater 



susceptibility to attacks of the screw worm. Besides, there 



is a quarantine inspection of cattle which restricts the shipping 



and importation of cattle, so that from all sources the loss is 



figured at $100,000,000 each year. 



Considering the losses from the fowl tick, spinose ear tick, 

 spotted-fever tick, and damage by ticks in general, it is prob- 

 ably not too much to say that ticks cost our country 8150,000,000 

 a year. 



Frequently an animal has more than one species of ticks 

 upon it. In such cases the ticks are usually of different 

 genera; thus Margarojpus, Dermacentor, and Amblyomma, or 

 Ixodes and Dermacentor, may be associated on the same host. 

 In some cases, as Ixodes, but few specimens occur on one host, 

 while in other cases, Margaropus and Rhipicephalus, hundreds 

 or even thousands attack one animal. As a result of her bloodthirsty nature the 

 female tick becomes enormously distended, and is then in a mature condition. 



The male tick does not enlarge, and 

 doubtless does not feed to such an extent 

 as his mate. The engorgement of the 

 female produces a characteristic shape to 

 the body in each species; thus-a Derma- 

 centor engorged is more elongate than an 

 engorged Ixodes. In some cases complete 

 engorgement depends uj^on fertilization. 

 The life history of ticks has been in- 

 vestigated by many authors, notabh' 

 Curtice, Morgan, Lounsbury, and Hun- 

 ter, Bishopp, and Hooker. The true 

 Fig. no.- Margaropus annulatus, male. Ixodidse engorge but once in adult life, 



(Author's illustration.) o\iposit, and then die. The Argasidse 



may engorge several times, ovipositing after each engorgement. In all cases the female 

 tick drops to the ground to deposit her eggs. These are usual ly placed upon the surface 

 of the soil or just beneath it. They form 

 an elongate massdn front of the tick, and 

 may be as many as 1,000 to 20,000 in num- 

 ber. The number probably varies con- 

 siderably, as the cattle tick deposits from 

 2,000 to 4,000. Several other ticks have 

 egg-laying records of over 2,000, and Mor- 

 gan has recorded 6,519 eggs for an Am- 

 blyomma americanum Linn, and Hooker 

 1] ,265 for Amblyomma maculatum Koch, 

 while two species of Dermacentor have 

 records of above 7,000 eggs each. The 

 Argasidae, however, deposit fewer eggs. 



Fig. 111.— Larva of Margaropus annulatus. 

 (Author's illustration.) 



and these are placed in batches of 20 to 50 eggs each. When the mother tick is abou fc 

 to deposit eggs she bends the capitulum downward toward the genital aperture; the 

 membrane between the capitulum and scutum is thus exposed and bulges out till it 

 extends over the capitulum in the form of two lobes. The ovipositor is extruded until 

 it comes in contact with the swollen membrane; it is then withdrawn, leaving: the es:s: 



