40 Journal Xew York Entomological Society, t^'"'- >^>^n. 



importance in distributing the species over considerable land areas. 

 Now comparison of specimens of closely allied species or of the same 

 species from high altitudes and sea-level shows that the mountain 

 forms have distinctly longer wings. To take only one common example, 

 females o/ Lasiiis nigcr L. var. americanus Emery from Wisconsin 

 and Illinois have the fore wings only 7.5-8.5 mm. long, whereas these 

 appendages in females of the same size and weight from altitudes of 

 7,000-8,000 ft. in Colorado measure 9.5—10.5 mm. This enlargement 

 of the wing membranes in mountain ants, which I shall consider in 

 more detail in a later publication, is most readily explained as an 

 adaptation to flight in a more rarified atmosphere. It seems not to have 

 been observed in other insects, probably because the enlargement is 

 slight, amounting only to one or two millimeters or to a fraction of a 

 millimeter. One would expect the rarified atmosphere of great ele- 

 vations also to have the reverse efifect on certain heavy bodied insects 

 and to lead to the suppression of flight and its organs altogether. 

 This seems to be actually the case in some alpine beetles, as has been 

 observed by several authors. One might be tempted to explain the 

 aptery of two of the Hidalgo ants (Monomorinm cyaneum and M. 

 comprcssinn) as the result of such an adaptation, were it not that such 

 females occur in several species of this genus {e. g.^ M. cbcninum 

 Fore! and M. floricola Jerdon.) that live only at low altitudes in 

 tropical or subtropical countries. 



Family FORMICID^. 



Subfamily POXERIX.E. 



1. Ponera inexorata Wheeler. 



A single dcalated female from San Miguel. 



2. Ponera trigona Mayr var. opacior Forel. 



Three workers from Guerrero j\Iill. 



3. Odontomachus haematoda L. subsp. clarus Roger. 



Numerous workers, a dealated female and a male found nesting in 

 the soil under stones at San Miguel. 



Subfamily DORYLIN^. 



4. Eciton coecum Latr. 



Numerous workers and males from Guerrero Mill. The latter 

 were taken at lights. 



