256 J. A. G. REHN 



ern and southeastern United States to develop distinct specific 

 entities. All non-adventive forms found west of central Texas and 

 Kansas clearly have entered our limits within geologically recent 

 times. 



ORDER ORTHOPTERA: SUBORDER CAELIFERA 

 Superfamily Acridoidea 



Family Tetrigidae. The Tetrigidae, or "grouse locusts," are 

 cosmopolitan, except for the true arctic and antarctic regions and 

 New Zealand ; they are even represented on some of the Pacific island 

 groups by distinctive genera. Although terrestrial in habits, they 

 almost invariably show close association with moist areas, and many 

 species are fully capable of sustaining themselves on the surface of 

 water, or of swimming beneath the surface. Their known paleonto- 

 logical picture is represented by a fossil genus in the Baltic Amber, 

 material referred to a Nearctic and Neotropical genus from the 

 Upper Miocene of Bavaria, and an unplaced species of the family 

 from African copal gum. 



Very narrowly within our limits, in coastal south Texas, there 

 enters the genus Neotettix, an endemic eastern and southeastern 

 North American assemblage, possibly developed relatively early, 

 either from a primitive Tetrix-\\\<.Q ancestor, or more probably from 

 the Neotropical genus Liotettix, to which it has some affinity. A 

 similar history is probably that of the Mexican and Central American 

 Ochetotettix, which is related to Neotettix and also to Liotettix, but 

 Ochetotettix does not enter our territory. Indications point to Neo- 

 tettix being one of the number of orthopterous genera apparently 

 derived from a relatively early, certainly pre-Pleistocene, invasion 

 from the Neotropics; most of these genera are now isolated in the 

 eastern or southeastern United States. 



The genus Tetrix, which is represented in western North America 

 by five distinct lines, is clearly of Palearctic origin, but it is warranted 

 to believe that our North American lines of the genus represent a 

 number of distinct incursions from the Palearctic, certainly one or 

 two much earlier than the last. From the earlier one or ones three of 

 our stocks have probably developed: T. arenosa, presumably the 

 earliest, is now confined to the eastern, central, and southeastern 

 United States and extreme southeastern Canada; T. ornata is much 

 more broadly distributed; T. sierrana, clearly related to Old World 



