432 SANITARY ENTOMOLOGY 



Host Relations. — Ticks develop upon a great variety of species among 

 the higher animals. Toads, lizards, snakes, and turtles are infested to a 

 considerable extent, birds are attacked by a number of species and espe- 

 cially by immature stages of forms which when mature attack larger 

 animals. Practically all mammals, from the small field mice to the pachy- 

 derms, ruminants, and man, are infested by ticks. In general those ticks 

 which remain on the host for their molts attack fewer species of 'animals 

 than those forms which pass their molt on the ground, and nearly all 

 ticks attack more than one host, but many species develop sticcessfuUy 

 only on certain related animals. These points are made use of largely 

 in practicing control or eradication. 



Relation Between Stages and Disease Transmission. — In connection 

 with the transmission of disease, the infective stages of ticks vary with the 

 species and the disease organism concerned. In the case of a number 

 of diseases, the organism passes from one generation to the other through 

 the egg. This is true in the case of the^ cattle tick and Texas fever and 

 also with Rocky Mountain spotted fever. With certain diseases the 

 adults only are infective and these derive the infection from the adult of 

 the preceding brood. Some disease organisms are taken up by the larvse 

 and transmitted by the nymphs or adults of the same generation. 



Life History and Habits. — Owing to the wide diversity in life history, 

 habits, and economic considerations among the ticks, it is thought best to 

 briefly outline some of the principal points along this line, treating the 

 matter according to species. 



The Fowl Tick, Argas persicus (Fischer Von Waldheim) miniatus 

 Koch (plate XXVI). — This is a serious pest of various kinds of poultry 

 and is tropicopolitan in distribution, usually being most abundant in the 

 semi-arid regions. In the United States it occurs in Florida, and from 

 Central Texas westward to the Pacific. It not only acts as a simple para- 

 site but is responsible for the transmission of a disease of fowls known 

 as spirochaetosis. It has been reported as attacking man, but can not be 

 considered of any special importance in this regard. 



The seed ticks remain attached to the fowls from four to ten days, 

 dropping at night and spending the remainder of their life hidden away 

 about the roosting places of the fowls, only venturing out to feed at 

 night. Several batches of eggs are deposited, engorgement taking place 

 after each deposition. These ticks are remarkable on account of the fact 

 that they can live over two years without food. They are also very 

 resistant to insecticides. 



There is another species of Argas A. reflexus (Fabricius) Latreille, 

 which is of considerable economic importance. This attacks pigeons. 

 Most of the other members of this genus feed upon birds and bats. 



The African Relapsing Fever Tick : Ornithodoros moubata ( Murray) 



