ENTOMOLOGY

432 SANITARY ENTOMOLOGYHost Relation8.-Ticks develop upon a great variety of species amongthe higher animals. Toads, lizards, snakes, and turtles are infested to aconsiderable extent, birds are attacked by a number of species and especiallyby immature stages of forms which when mature attack largeranimals. Practically all mammals, from the small field mice to the pachyderms,ruminants, and man, are infested by ticks. In general those tickswhich remain on the host for their molts attack fewer species of animalsthan those forms which pass their molt on the ground, and nearly allticks attack more than one host, but many, species develop successfullyonly on certain related animals. These points are made use of largelyin practicing control or eradication.Relation Between Stages and Disease Transmission.-In connectionwith the transmission of disease, the infective stages of ticks vary with thespecies and the disease organism concerned. In the case of a numberof diseases, the organism passes from one generation to the other throughthe egg. This is true in the case of the cattle tick and Texas fever andalso with Rocky Mountain spotted fever. With certain diseases the