30 Irans. Acad. Sci. of St. Louis. 



is true that in the Analgesidae we may have a single 

 species found on hosts belonging to different families, or 

 even in a few cases to different orders, but never are 

 these forms found on other hosts than birds. That a 

 single species like Ixodes ricinus Linn, has been found 

 on such widely separated hosts as bats, birds, hedgehogs 

 and man shows that they possess most of the characters 

 necessary for a wide host distribution. Perhaps the most 

 important point in this regard is their peculiar adhering 

 apparatus. This consists of a strong, dartlike hypos- 

 toma with prominent recurved teeth. This structure, as 

 can easily be seen, is capable of being inserted with about 

 equal ease into the skin of a mammal, a bird, or a reptile ; 

 this is in marked contrast with the clinging apparatus of 

 Myobia, which can only be used upon a single mamma- 

 lian hair, and that of a definite size. Then the ticks pos- 

 sess good walking legs, have a very tough skin, are re- 

 sistant to temperature changes when off a host. Being 

 blood suckers, they can engorge themselves with blood, 

 drop to the ground and live for months upon this meal. 

 Again the females are enormously prolific, laying in 

 some cases as high as 10,000 eggs. These eggs usually 

 hatch uponthe ground and the young are given oppor- 

 tunities to find various hosts, each for himself. In clos- 

 ing my remarks about this group it might be safe to say 

 that almost every condition necessary for a great range 

 in distribution among host species has been fulfilled in 

 regard to it. 



A List of the Species of Listrophoridae Which Have 

 Been Recorded from More than One Host Species, 

 'Together with Their Hosts. 



listrophorus Pgst. 



L. gihhus Pgst. — Lepus cuniculus, L. timidus L. 



L. mustelae M6gn. — 'Mustela valgaris Erxl., M. erminea L., M. putorlus 



L., also on pole cat. 

 L. leuckarti Pgst.— Paludicola terrestris (L.), P. amphlbius (L.), Arvlc- 

 ola arvalls (Pall.), Mus sylvatlcus L. 



