ENTOMOLOGICAL SECTION. 



Notes on the " Biologia Centrali-Americaiia." 



BY OEO. H. HORN, M. D. 



Students of the natural history of the North American continent 

 have niucli to be thankful foi' in the progress of the im])ortant work 

 undertaken under the editorship of Messrs. Godman and Salvin, with 

 the collaboration of those whose names scarcely need any. additional 

 lustre from the " Biologia." 



The work aims to embrace that portion of the continent of North 

 America south of the boundary line of the United States and in- 

 cluding the Isthmus of Panama. From a political stand-point the 

 Peninsula of California should have been included, but it has been 

 (emitted, from the fact that many of the species have been described 

 by Dr. LeConte and myself, showing that the fauna of that region 

 (with the exception of the extreme southern end) is much more 

 closely related to our Arizona region than would be any similar 

 .southern extension from the boundary line of Arizona. 



The territory along the boundary line is for the most part an in- 

 hospitable region — hot, dry and barren, with occasional more or less 

 fertile valleys extending in a general direction N. W. to S. E. Some 

 of these valleys are pi'operly Arizonian extensions, others extend 

 u})wards from Mexico. The latter case prevails in the northwestern 

 portion of Mexico, while the reverse exists in the northeast, in the 

 region west of the Rio Grande. This results in a preponderance of 

 the species of the region from which the fertile peninsula arises. The 

 broad belt of desert, hot and rainless, east and southeast of Fort 

 Yuma seems to act as an effectual barrier against the intermingling 

 of the species of the two faunas to any notable extent. 



The collection made by Morrison teaches very little. How far he 

 went below the boundary I do not know, although my series was 

 purchased as from Arizona purely, and the same series is quoted by 

 the authors of the " Biologia" as from northern Sonora. With very 

 few exceptions the series was such as we are accustomed to meet in 

 Arizona with no greater admixture of Mexican forms than we find 

 on the Texas side of the Rio Grande. 



