VU1 INTRODUCTORY REMARKS. 



So far as we know, the southern and colder regions of the con- 

 tinent of South America, Patagonia, and the south of La Plata 

 supply no representatives of the groups described in this volume*, 

 the limits of their distribution throughout the world being appa- 

 rently, in the south, 32 or 34, and in the north, 40. The Euro- 

 pean species are found, as has been noticed, in the south of Portugal 

 and Spain (that is, between the degrees of 36 and 38) ; although on 

 one occasion I took examples of Lithonoma cincta, Fab., at Bar- 

 quero, on the Asturian shores of the Bay of Biscay, in latitude 43 

 nearly t. 



But between these limits the group would appear to be generally 

 distributed-, we have no reason to suppose the existence of any 

 special numerical centre or centres ; wherever the district has been 

 examined, there species have been found to be indigenous, and the 

 number of species discovered always bears a fair proportion to the 

 amount of labour and patience that has been expended in research. 

 Thus (and thus solely) we have more species from the neighbourhood 

 of Eio Janeiro than from any other three or four localities united ; 

 not because the province of Eio is a focus where examples of this 

 group especially abound, but because in other provinces we have 

 not had the advantages of the residence of such zealous and able 

 naturalists as Mr. Fry and Mr. Miers. 



Thus, also, the district of the Amazon supplies to us, in this and 

 other groups, more new genera and species than the districts of 

 Bahia and Pernambuco ; but only because we still have to find some 

 one who, impelled by an earnest love of nature, will devote himself 

 to the exploration of the basin of the San Francisco River with the 

 same patient energy that has been manifested by Mr. Bates in his 

 researches during many years in the district of the Amazon. 



In considering, with reference to this group, the interesting ques- 

 tion as to the probable amount of influence exercised by tropical lati- 

 tudes on the size and the brilliancy of species, as contrasted with 

 subtropical latitudes, our present very imperfect knowledge of the 

 fauna of the Continent as a whole will not permit more than the 



* In Chili, which ranges from 40 to 34, a single species has been detected, 

 Hypolampsis melanotus. 



f The isothermal line of 43 in Spain, however, is the same as that of 36 N. 

 in the United States. 



