484 PROCEEDINGS OF THE ACADEMY OF [Oct., 



and fall far short of giving a complete picture of the Odonate fauna. 

 It is also clear, especially from the Cuernavaca list, where the same 

 species appear at frequent intervals throughout the year, that a num- 

 ber of different, perhaps overlapping, broods must exist, as there is no 

 reason for supposing that the life of an individual imago is prolonged 

 for many months. 



Rainfall and Odonata on the Atlantic and Pacific Slopes. — Various 

 authors^^ have remarked the greater abundance of species of animals, 

 including insects, on the Atlantic than on the Pacific slope of Mexico 

 and much of Central America. Sumichrast {I.e., p. 5) has attrib- 

 uted the relative poverty of the Pacific slope of Tehuantepec and 

 adjoining areas in birds to "the extreme dryness of the soil; to the 

 scarcity of vegetation and of insect life; and to the duration of the 

 \vinds from the northeast and southwest which there prevail with great 

 violence." Harrington^^ has concluded that for Central America, 

 "The rainfall is greater on the Atlantic than on the Pacific side as two 

 or three to one." Table 11 gives the distribution of the Odonata 

 on these sides and on the Mexican plateau for the whole of our district, 

 from which it appears that the total nimiber of Atlantic slope species 

 is 235 against 181 for the Pacific, a proportion of nearly 4 to 3. Tables 

 6-8 (pages 471-473) give the proportions for Mexico, Guatemala and 

 Costa Rica respectively as, approximately, 4 to 3, 4 to 2, 4 to 4^. 



Neither the rainfall nor the Odonate fauna can be summarized bo 

 briefly, however, as local conditions may cause both of these to vary. 

 Not only the map of Puga,^^ but also the publications of Sapper^^ and 

 of Lottermoser^^ show as heavy a rainfall on parts of the Pacific slope 

 of Mexico and Guatemala as on the Atlantic side. The Odonate 

 fauna of Altamira and Tampico, in Tamaulipas, numbers 40 speciea- 

 that of Tepic 42; for Jalapa, Vera Cruz, we know 24 species, for Guada; 

 lajara 50; for the vicinity of the city of Vera Cruz, including Medellin, 



32 Sumichrast, quoted by Lawrence (Bull. U. S. Nat. Mus., No. 4, 1876) for 

 birds of the Isthmus of Tehuantepec. Godman (Biol. Cent. Amer. Lepid. Rhopal., 

 I, p. vi, 1901) for Lepidoptera Rhopalocera generally "to perhaps as far south as 

 Costa Rica." V. Martens (Biol. Cent. Amer. Land and Freshw. Moll., p. xxvii) 

 for this group to the same distance; he correlates the greater abundance of 

 species -nith the greater area of the Atlantic slope of Mexico, Guatemala, Hon- 

 duras and Nicaragua. Champion (Entom. News, XVIII, p. 33, 1907) for insects 

 of Guatemala. 



=3 Bidl. Philos. Soc, Washington, XIII, p. 7, 1895. 



^* " Distribucion de las Lluvias en la Republica Mexicana," Mem. Soc. Cien., 

 ".\ntonio Alzate," XVI, 1901. 



3^ Petermann's Mitth., XLIII, pp. 117 et seg. and map, 1897; Das Nordliche 

 Mittelamerika, pp. 182-3; Mittelamerikayiische Reisen u. Studien, pp. 299-300. 



58 Meteorol. Zeitschr., XXIII, pp. 237 et seq., 1906. 



