30 CALIFORNIA ACADEMY OF SCIENCES. 



flattened and more angular prothorax, the stouter scale, 

 finer pubescence and in the coloration of antennas and 

 legs. 



Described from many specimens, taken at San Esteban, 

 San Jorge, El Paraiso, San Julio, San Jose de Gracias 

 and San Jose del Cabo. 



6. Myrmecocystus mexicanus Wesm. 



Myrmecocystus mexicanus Wesm., Bull. Ac. r. sc. et bell. lett. 

 Brux., V, 1838, p. 770. 

 One . Santa Maria. 



7. Dorymyrmex pyramicus Rog. 



Prenolepis 2^yramicus Kog., Berl. Ent. Zts., 186.3, p. 160. 

 Formica insana Buckley, Proc. Ent. Soc. Phila., 1866, p. 165. 

 Dorymyrmex insanns McCook aud var. favus McCook, Cotton Ins., 

 1879, pp. 185 and 186. 

 Two ^ . Magdalena Island. 



Differs from the typical form only in the entirely black 

 antenna? and legs. 



8. Tapinoma sessile Say, var. 



Formica sessile Say, Boston Jouru. N. H. S., I, p. 287. 



TajMnoma boreale Eog., Berl. Ent. Zts., 1863, p. 165. 



Tapinoma boreale Mayr, Myrm. Beitr., Sitzb. d. k. Acad. d. Wis- 



seusch., liii, 1866. 

 Formica parva Buckl., Proc. Ent. Soc. Phila., 1866, p. 159. 



Fifteen 5 ^ . Margarita Island and San Jorge. 



The genus Tapinoma, as far as known at present, is 

 represented in North America by but one species with 

 numerous varieties, varying in size and coloration, all of 

 which pass so gradually from one to the other that it is 

 almost hopeless to separate them satisfactorily. The 

 present form is smaller and paler than most of those 

 found in the United States, and comes nearest to var. T. 

 boreale Rog.; I hesitate, therefore, without having a 

 knowledge of the sexes, to describe this form as new. 



