CHAPTER I. 



GEOGRAPHICAL DISTRIBUTION AND DISPERSION OF LEPTINOTARSA. 



The Genus LEPTINOTARSA. 



The genus Leptinotarsa Stal is one of a number of closely allied genera 

 which constitute the major portion of the Chrysornelid fauna of America 

 north of the Isthmus of Panama. In the Mexican and Central American 

 regions 13 genera and about 225 species are known. Of these all but 

 Phcedon, which is a genus of cosmopolitan distribution, are entirely confined 

 to the American continents, and several of them to North America. The 

 genera and their distribution in Mexico and Central America are given in the 

 following table : 



Table i. Distribution of the Genera and Species of Chrysomelidas in 

 Mexico and Central America. 



With the exception of Phcedon, all of these genera are so closely allied that 

 only trivial characters are used as generic differentials, and these are often 

 highly variable. Within the genera the species form groups, or series, 

 about some central type, and the same type is often found running through 

 several genera. The slight generic differences, the still less pronounced 

 specific characters, and the continuity of the series are strongly suggestive 

 of a recent origin, or at least of a recent rise of species, which may still be 

 going on. 



