DIMORPHISM IN BLISSUS LEUCOPTERUS. 



333 



joined the Mississippi Valley branch in northern Ohio and around 

 the Great Lakes. 



The short-winged form, so far as known in America, is con- 

 fined to the ocean coasts and the immediate vicinity of the Great 

 Lakes. The vast interior region from Central America to Mani- 

 toba abounds with only the long-winged form. 



If Webster's theory is the correct one, we can scarcely escape 

 the conclusion that the short-winged form originated in the re- 

 gions where it is at present found. No short-winged specimens 

 have ever been reported from the Gulf States outside of Florida, 

 from Mexico or Central America, nor west of the Alleghanies, 



notwithstanding, the insect is common in those regions and the 

 short-winged form has been carefully looked for in some of them. 

 The long-winged insects, then, appear to have been the ancestral 

 form in America as far as history and hypothesis can give a clue. 

 There seems to be an inherent tendency in the species to produce 

 the short-winged form when the proper ecological conditions are 

 provided. How the species acquired this tendency is a very 

 difficult thing to understand and it is not the purpose of this 

 paper to attempt an explanation of a phenomenon that appears 

 to be older than the division of Heteroptera into the present 

 recognized families. 



According to Saunders l dimorphism is exceedingly common 

 among British Heteroptera and this caused much confusion 



1 Saunders, Edward, F.L.S., "The Hemiptera Heteroptera of the British Is 

 lands," 1892. 



