310 THE UNIVERSITY SCIENCE BULLETIN. 



tion as this species has been taken only a single time in the 

 state. 



It is very likely that with more thorough and extensive col- 

 lecting several more species will be found in Kansas. The 

 writer has been greatly impressed with the number of cicadas 

 that apparently reach one of the limits of their geographical 

 distribution in the state. Thus the Kansas members of the 

 western genus Okanagana seem to reach their eastern limit in 

 the state. Similarly the eastern and southern genus Tibiclna 

 seems to reach its western limit with us. Various members of 

 the genus Tibicen also just enter Kansas. Thus we have T. bi- 

 fidus reaching eastward into the western counties. The eastern 

 T. pruinosa seems to be very common in eastern Kansas but 

 does not occur in the western part. The eastern and southern T. 

 lyricen seems to reach its northwestern limit in the southeast- 

 ern counties of our state. The southern T. vitripennis reaches 

 its northern limit in the southern counties. The relatively 

 eastern T. marginalis is found in the eastern two-thirds of the 

 state, while the closely related T. dealbata evidently does not 

 go much further east than central Kansas. Again, T. linnei 

 seems to reach its western limit with us while T. superba and 

 T. eugraphica are not found further north. Proarna venosa 

 likewise finds its northern boundary in the state, and Tibici- 

 noides hespcrius is confined to the western counties and likely 

 reaches its eastern limits with us. 



This convergence in one state of so many species of varied 

 distribution is undoubtedly due to its central geographical posi- 

 tion, to the extremes of its rainfall, and to its varying eleva- 

 tion. Thus the eastern part of the state is distinctly mesophy- 

 tic, starting with an elevation of 800 feet and with an average 

 rainfall of as high as 45 inches. This condition gradually 

 changes as one goes west over the gradually rising and drier 

 portions of the state, till at its western border the elevation has 

 reached 3,600 feet and the average rainfall has decreased to as 

 low as 16 inches. With this change one finds a corresponding 

 change both in the flora and fauna which is very evident even 

 to the casual observer, at least as far as the flora is concerned. 

 This latter change, combined with those causes which produce 

 it, is undoubtedly responsible for the variety of insect forms 

 and their distribution in the state, for it has repeatedly been 

 found that in many if not all groups of insects, the eastern and 



