9 8 natural history bulletin. 



its port, Point Isabel, lies a range of low hills — the "yucca 

 ridges " — on which the growth of vegetation is that charac- 

 teristic of the arid regions of the Lower Sonoran, great yuc- 

 cas mingled with the usual legumes, mesquite, huisache and 

 screw-bean. Here the insect-fauna takes on a character befit- 

 ting its surroundings and we find the genera, often indeed the 

 species, which occur in like situations in Arizona and Mexico. 



Between these hills are wide valleys, salt in character and 

 either baked dry and hard or covered more or less completely 

 by the peculiar succulent plants common in such situations 

 elsewhere in the west. These salt-flats extend in a somewhat 

 broken sequence completely to the sea-coast at Point Isabel 

 and support a few forms of insect life more or less peculiar to 

 themselves. Reaching the Point, the long sand-beaches here 

 and on Padre Island (across the narrow bay) are inhabited by 

 a true maritime fauna, part of which may be called tropical in 

 in its nature while the remainder is identical with that of the 

 Gulf coast further north. All of the localities mentioned were 

 visited by the writer, and some description of them is essential 

 to a real understanding of the complex character of the 

 Brownsville insect-fauna. 



Regarding the true affinities of the Coleopterous fauna and 

 the claim of the region to be considered tropical in its nature, 

 opinions are more or less divided. Mr. Schwarz has stated, 

 in the paper previously quoted, that "no one can doubt the 

 existence of a semitropical insect-fauna along the north bank 

 of the lower Rio Grande." Prof. Townsend 1 classes the 

 Brownsville fauna as Lower Sonoran — with a considerable 

 touch of Austroriparian and about twenty-five per cent trop- 

 ical. Dr. Merriam 2 has included it in his Tropical region. 

 Dr. LeConte, 3 writing thirty-seven years ago, speaks of it as 

 a "sub-tropical province." 



Looking through the list of species belonging to the five 

 families treated in the present portion of this report, it seems 



1 Transactions of the Texas Academy of Science, 1895, p. 85. 



2 Proc. Biological Society of Washington, Vol. vn., p. 33 and map. 

 3 Coleoptera of Kansas and New Mexico: Smithsonian Contributions. 



