t 



March, 1914.] WhEELER: AntS FROM HiDALGO,, IMeXICO. 39 



2. Thirty-four of the thirty-nine forms enumerated in this paper, 

 or 87 per cent, nest under stones. The exceptions are the two species 

 of Myrmccocysfus and Pogonomynncx barbafits, which make crater 

 nests in the ground, Pseudomyrma flavidula, which nests in hollow 

 twigs and Camponotus nitidus, which lives in wood. 



3. Equally striking is the pronounced melanism, which in a large 

 proportion of Hidalgo ants is not only very apparent in the males 

 and females, but extends also to the workers. This phenomenon is 

 observable in fully twenty-nine, or 74 per cent, of the forms. The 

 only ones in which a decided increase of pigmentation is not apparent 

 in the worker phase, are Odontomachus darns, Ponera inexorata, 

 Eciton ccccum, Pseudomyrma, flavidula, Solcnopsis minutissima, Pogo- 

 nomxrmcx barbatus, Lasius mexicanus and Formica nahua. In four 

 of these, the species of Ponera, Eciton, Solcnopsis and Lasius, the 

 worker, as shown by the vestigial eyes and pale coloration, is hypo- 

 gasic in habit. The absence of melanism in the few remaining species 

 is not so readily explained, but is also probably associated with 

 peculiarities of habit. 



Undoubtedly this pronounced melanism in the ants of Hidalgo is 

 due to the intensive and protracted insolation to which they are sub- 

 jected at the high altitudes in which they live. The same peculiarity 

 has been noticed in alpine insects in Mexico and other parts of the 

 world, in mollusks, birds and mammals. Herrera and Lope call 

 special attention to it in their voluminous work on the plants and ani- 

 mals of the IMexican plateau. ^ 



It is interesting to note that Mr. Mann, who is preparing a paper 

 on the Hidalgo myrmecophiles notices a high degree of melanism in 

 some of these, especially in a species of Xenodusa (X. sharpi) and in 

 two other Staphylinids of the genera Dinardilla and Apteronina, which 

 live with Liometopum apiculatum, itself a melanistic, subalpine species. 



4. Still another peculiarity, which has impressed me while working 

 on the Hidalgo ants, is the great lejigth of the wings in the females, 

 especially when these have large heavy bodies, as in the genera 

 Pheidolc, Lasius, Camponotuus, etc. Of course nearly all heavy bodied 

 female ants have long wings, to facilitate the nuptial flight, which not 

 only serves to unite the sexes from different nests, but is of very great 



2 Herrera, A. L., and D. Vergara Lope, La Vie sur les Hants Plateaux. 

 Mexico, L Escalante, 1899, 790 pp., iii plates, 19 tables. 



