Z ENTOMOLOGICAL SOCIETY 



subdivision,* but with marked affinities to the austroriparian 

 region. 



The valley of the Rio Grande nowhere forms a natural divid 

 ing line, and the flora and fauna of southwestern Texas extend 

 into the State of Tamaulipas how far south, I am unable to state. 

 The explorers of the Mexican fauna have entirely neglected this 

 region, and only a few representatives thereof are recorded in 

 the Biologia Centrali-Americana. 



That a number of genera and species of animals belonging to 

 the neotropical region extend northward along the tierra caliente 

 of eastern Mexico and cross the Rio Grande into Texas has long 

 since been recognized, but since nothing definite regarding the 

 exact extent of the region where this tropical fauna is to be found 

 north of the Rio Grande seems to be known, at least so far as 

 the insects are concerned, I venture to place on record a few ob 

 servations made by myself during a very short visit to the lower 

 Rio Grande in June, 1895. 



Collections made at Laredo, San Diego, Corpus Christi, and 

 in the lower Nueces river valley prove that, with few exceptions, 

 no tropical forms occur in that section, and the trip on the stage 

 from Alice to Brownsville shows that the character of the coun 

 try does not change southward until the black alluvial soil of the 

 delta of the Rio Grande is reached. Here, within the bends of 

 the river, as well as along: the various backwaters and old river 



O 



arms (resacas) which dissect the delta, isolated areas or strips of 

 larger or smaller extent are covered with a dense forest having 

 thick undergrowth of varied shrubbery and a rich vegetation of 

 lower plants, the like of which is not seen at any other place in 

 southwestern Texas. These forest jungles (in Florida they would 

 be called hammocks) are the home of the semi-tropical insect 

 fauna of Texas, which, so far as known to me, has, previous to 

 the year 1895, never been investigated by any entomologist, since 

 even many of the most abundant species are either entirely new 

 or not yet recorded from the United States. If, confining myself 

 to Coleoptera found by Prof. Townsend or myself near Browns 

 ville, I mention the genera Agra, Dasydactylus, Physorhinus, 

 Achryson, Gnaphalodes, Amphionycha, Megascelis, Plectrotreta, 

 Brachycoryne, Listronychus, Polypria (quite a number of others 

 are not yet determined, or undescribed), no one can deny the ex 

 istence of a semi-tropical insect fauna along the north bank of the 

 lower Rio Grande. The number of species composing this fauna 

 is very large ; in Coleoptera alone I estimate that, after proper ex- 



* Prof. E. D. Cope, in his paper " On the Zoological position of Texas " 

 (Bull. 17, U. S. Nat. Museum, i8So), calls thi region th<? Texas district 

 of the austroriparian fauna." 



