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IV 



INTEODUCTION. 



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by recent discoveries. The reason of the comparative paucity of Carabidse in the Tropics 

 has been supposed, apparently on good grounds, to be that their place, as predaceous 

 terrestrial insects, is to a great extent occupied by the ubiquitous ants. The undoubted 





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fact that purely epigseous Carabidse, except marsh species, are 



the Trop 



especially near the Equator and in the low-lands, and that arboreal or climbing forms 



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alone are numerous and varied, affords support to the hypothesis. 







The essentially Neotropical character of the Central- American fauna is generally 

 admitted, and is strikingly confirmed by the Cicindelidse and Carabidse, no fewer than 

 62 out of the 154 genera being purely tropical American forms, besides 31 others which 



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are chiefly Neotropical, although extending a smaller or greater distance into the tem- 

 perate zone north or south, chiefly north. A further series of 15 genera belonging to the 



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Tropics of both hemispheres ought also to be included, as they appear to have spread 



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north from the Neotropical zone ; thus making a total of 108 tropical genera in the 

 fauna. This leading feature may be considered therefore well established ; but with 

 regard to the northern limits of the fauna, and especially the extent to which Nearctic 



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and North-temperate forms have penetrated the region from north to south, these 

 are points not yet settled . Wallace, in his ' Geographical Distribution of Animals ' 

 (vol. i. p. 79, and Map, vol. ii. p. 115), included, or seemed inclined to include, the 

 whole of the central highlands of Mexico and Guatemala in the Nearctic province, 

 which must mean that North-temperate American forms are there in the majority. 

 Our two families of Coleoptera do not support this conclusion. It is true that a consi- 

 derable number of northern genera occur in Central America, and not in the tropical 

 region further south ; but the purely Nearctic forms are comparatively very few, and at 

 least in the middle zones of altitude (the "tierras templadas") are far out-numbered by 



pical g 



The total number of northern genera in the fauna is 26, of which only 



10 are purely Nearctic, 16 being North-temperate. 22 out of the 26 do not pass south 



of Guatemala, and 15 



south of Mexico, the remaining 4 extending to Nicarag 



Costa Rica, or Panama. Of Neotropical genera (excluding such as pass into temperate 

 North America) Mexico possesses 37. A few genera, three in number, viz. Pelecium 

 Trichopselaphus, and Euchroa, belonging to Mexico, occur elsewhere only in the hilly 



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regions of South Brazil. If we analyze the species the result is still more conclusive as 

 to the distinctness of the Mexico-Guatemalan fauna from that of the Nearctic province, 

 the number common to the two regions being exceedingly restricted. 



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The northern limit of the Central- American fauna appears to be — on the central 



highlands if not also on the maritime lowlands east and 



tical frontier of Mexico 



little south of the poli 





This is indicated pretty clearly by two collections acquired for 











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