4s8 proceedings of the academy of [oct. 



Relations of the Odonate Fauna to Altitude. 



Table 9, page 476, in connection with the map (Plate XXVI), may be 

 used as indicating not only temperature zones, but also the elevated 

 or non-elevated character of the country in which Odonata have been 

 found, the higher zone numbers corresponding to higher altitudes. 

 Zone II in Central America and in Mexico south of 20° N. Lat. (25° 

 N. Lat. on the Pacific side) embraces all the low coast lands. The 

 highest point on the Atlantic slope of Mexico to which it attains 

 appears to be Actopan,^^ in Vera Cruz (311 m.*^), whence it descends 

 to sea-level south of Tuxpan, while on the Pacific slope it reaches 487 

 m. at the city of Colima^^ and sea-level north of Culiacan. Its upper 

 limit in Central America is about 270 m. 



North of zone II the coasts of Mexico fall in zone III, which, 

 with the higher parts of zone II, includes everywhere the gradually 

 ascending slopes of the central plateaus and mountain ranges to an 

 elevation of about 1,160 m. in Central America, 1,560 m. at Oaxaca 

 City, 1,000 m. at Mirador, Vera Cruz, 700 m. in Nuevo Leon and higher 

 than this last in Sonora. 



In zones IV and V the larger rivers arise, to descend (except in some 

 parts of northern Mexico) through zones III and II to the sea. Zone 

 IV extends to an elevation of 2,050 m. in Central America, 2,200 m. 

 in the southern part of the Mexican plateau, but to not above 1,200- 

 1,300 m. in places in New Mexico. 



The only species which appear to be exclusively confined to the 

 actual sea-coast are ^shna brevifrons, Erythrodiplax berenice nceva 

 and Tramea longicauda var. Libellula auripennis is chiefly a sea-coast 

 species, but in Mexico, as in the United States, has been found elsewhere. 

 A larger number (16)^" of forms are not known to descend below the 

 lower limits of zone IV and are, in our district, markedly highland 

 species. Such are Hetaerina tolteca, H. maxima, Cora skinneri, 

 Lestes henshaioi, Argia terira, herberti, chelata and tonto, Pro- 

 gomphus obscurus borealis, Cordulegaster godmani, >Eshna dugesi, 

 Plathemis subornata, Libellula comanche, foliata, nodisticta and luctuosa. 

 The remaining 274 forms have an intermediate or a more varied habitat, 



" Moreno y Anda and Gomez, El Clima de la Republ. Mex., Ano II, p. 136. 



*^ Revista Soc. Cien., "Antonio Alzate," XXIII, pp. 31, 32, 1905. 



" Hann, Hdh. d. Klimatologie, lite Aufgabe, II, p. 286. 



*° The apparent discrepancy between tliis figure (16) and that to be obtained 

 (19) from Table 9, page 476, is due to the fact that the three other species or 

 varieties, Anax longipes and Erythrodiplax connata a' and c' , while as yet found 

 only in zone IV in Mexico and Central America, have been taken at lower levels 

 in South America or in the West Indies. 



