ACARINA. 



S49 



Kt 



FIG. 560. Oral apparatus of Irodes 

 (after Al. Pagenstecher). Kf cheli- 

 cera ; Kt pedipalpus ; B' first pair of 

 legs. 



concealed from above, stigmata between the two last pair of legs, integu- 

 ment leathery and granulated ; eyes may be present. 



This and the next family are most formidable foes both to man and 

 domesticated and feral animals. They convey a Protozoan parasite, which 

 is as a rule a species of Pirosoma, from 

 one host to another just as Anopheles 

 conveys the malaria organism. No- 

 thing is known as to what goes on in 

 the body of the tick as the parasite 

 cannot be found there ; perhaps it 

 breaks up into ultra-microscopic spores, 

 but it is known that in the case of 

 Texas fever an infected female tick 

 can infect her eggs and that these give 

 rise to infected larvae. The members 

 of this family attack mammals and 

 birds, especially the latter. Argas with 

 8 species (Fig. 551). A. persicus at- 

 tacks man in Western Asia often with 



fatal results. Ornithodoros with 1 1 species has one European representa- 

 tive O. talaje. Like the Ixodidae the members of this family seem to 

 flourish best in warm climates. 



Fam. 5. Ixodidae.* The terminal rostrum comprises (1) a basai 

 portion, (2) a pair of pedipalps, (3) a hypostome beset with recurved hooks, 



and (4) a pair of 

 chelicerae, cutting 

 instruments with 

 serrated outer bor- 

 der. The sucking 

 tube is between the 

 hypostome and che- 

 licerae. Integument 

 leathery, stigmata 

 behind the coxae of 

 the last legs, male 

 very much smaller 

 than the gorged 

 female, the latter is 

 when young flat- 

 tened but the de- 

 velopment of the 

 eggs, aided by the 

 sucking of blood, 

 brings about an 

 enormous increase 

 in size and the body may attain the size of a filbert. The males are enclosed 

 in a dorsal shield which does not permit them to swell as the females do. 

 The larvae of most ticks live upon and amongst plants, but they readily 

 seize hold of passing animals and thrust their rostrum into the victim's skin. 

 The Ixodidae are parasitic upon mammals and to a less degree on birds and 

 reptiles, but the several species are catholic in their tastes and do not confine 



FIG. 561. Hyalommt aegypti-um, under side, o Chelicerae ; b 

 pedtpalpi ; c genital aperture ; d anal aperture ; 1-7 joints 

 of leg. 



* Neumann v. supra. 



Z III 



3 I 



