





INTRODUCTION. 



V 



the purposes of this work, one made by Forrer near the north-western frontier, and the 

 other by Morrison at a locality sixteen miles south of the Arizona border-line ; both 



s 



were remarkable for the predominance of purely North- American species, very few of 

 which were contained in other collections made by Forrer further south, near Ciudad 

 in Durango, and Hepburn in Coahuila, and were still more strikingly dissimilar from 

 collections made in Central Mexico. We know, however, very little at present of the 

 Coleoptera of Northern Mexico. 







One more question with regard to the relations of the fauna may be, in conclusion 



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briefly touched upon 



Does the Central-American fauna constitute one homog 



province or is it divisible into two subprovinces, as Mr. Salvin has shown to be probably 

 the case with regard to the birds, many genera of which are represented by distinct 



species on each side of a line which 



inclined to place north of the Nicarag 



lakes and their outfall the Kio San Juan % The distribution of the Coleopterous families 

 treated of in this volume would seem to justify this subdivision. I have just now 

 stated that only 4 out of the 26 northern genera pass to the south of Guatemala ; the 

 tropical genera of the fauna are not similarly limited in range, for out of the 108 genera 

 included in this category only about 30 are not spread over both the great divisions of 

 the region ; but if we analyze the species, taking as good cases some of the largest genera, 

 the difference between north and south is strongly marked. Thus out of 145 species of 

 Colpodes, 101 are peculiar to Mexico and Guatemala, and 32 to the States further south, 

 12 only being common to the two subfaunas. In another genus, relatively equally well 



presented 



the fauna, viz. Cicindela, repr 



62 species, 47 do not rang 



further south than Guatemala, 7 only are peculiar to the southern section, and 9 are 

 common to both subfaunas. Neither of these genera is exclusively Neotropical or 

 even tropical, and they differ remarkably in the range of their species outside Central 



America, for whilst 



of the Central- American species of Colpodes appears 



the northern boundary of Mexico, no fewer than 12 of the species of Cicindela are 

 common to the two regions, being mostly Nearctic species which extend their range to 



the northern parts of Mexico. Lebia is a genus of similar general range to Cicindela,. 

 and yields similar results ; for, of its 86 Central- American species, 54 are restricted to 

 Mexico and Guatemala (4 of them only being also North- American), 20 to the southern 



.bp 

 .bp 



(of which 10 



also South-American), and 12 being common to both 



•ovinces. Calosoma, a genus also of nearly world-wide distribution, has 20 Central- 

 American species, of which no fewer than 17 are peculiar to Mexico alone, and form 



of the most distinctive features of its Coleopterous fauna 



only are common 



Mexico and North America, and 



West-Indian species. Another genus may 







be 







of different character, i. e. purely Neotropical, viz. Agra : of the 31 Central 





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