232 IOWA ACADEMY OF SCIENCE Vol. XXV, 191^ 



half of the United States wouUl inchule all of the territory east 

 of the Rocky Mountains except the arid prairie counti-y. 



Iowa lies in the Austral life zone which is composed f-f three 

 ti'ans-continental belts, the Transitional. Upper Austral and the 

 Lower Austral. The Transitional belt dii^s down into northern 

 Iowa, extending as far south as CharlCiS City. The fauna of this. 

 belt Ls both Boreal (northern forms) and Austral. Ames lies 

 but one hundred miles .south of this zone, yet not a sinole 

 rorthern species has been collected, althouiih all of the forms in 

 the firet two columns of the table are found throu^liout the 

 entire transitional belt. 



On the other hand consider the Lower Austral belt, wliich 

 cuts throuuh Arkansas and extends north along Mississippi and 

 ]\Iissouri rivei>i a short distance. Ames is situated more than 

 two hiuidred mile« from the northern limits of this zone and yet 

 there are present three species which are stictly soutliern in 

 their range. 



This would seem to be an unusual state of affairs were it not 

 a well known fact that animal and insect migrations tend to fol- 

 low water courses. Our southern species could have :oll()wed 

 the Mississippi until they struck the Des ^loines at the junction 

 of these two rivers and from there found tl'cir way up into 

 this country. 



The MTiter has done considcralile work on the spiders of all 

 families collected in the vicinity of Ames and this paper is but 

 preliminary to a work on the entire spider fauna of Iowa. 



Althfmgh this is not the first work on sjiiders which has been 



