262 CALIFORNIA ACADEMY OF SCIENCES  [Proc. 4TH Ser. 
of the species, Monomorium pharaonis, Tetramorim guin- 
cénse and simillimum, Tapinoma melanocephalum, Prenolepis 
longicornis and P. vividula itinerans, are well-known tropical 
“tramps”, evidently introduced by commerce within recent 
times. Not improbably three others, Solenopsis genunata, S. 
sevissima and Camponotus senex, have been similarly intro- 
duced. Only nine species, therefore, would seem to be clearly 
indigenous to the islands. All of these are distinctly neo- 
tropical in their affinities and all but three, or possible four 
of them, namely Pheidole williamsi, Pheidole species, Cam- 
ponotus macilentus and C. planus, are either well-known 
species, widely distributed in tropical and subtropical portions 
of America, or merely subspecies or varieties of such forms. 
Nevertheless, if we consider the distinct forms, no fewer than 
26, or 72.2%, of the 36 are endemic, and these forms would 
undoubtedly rank as true species if the same estimate were 
applied to the subspecies and varieties of ants as is applied 
by the ornithologists and mammalogists to their taxonomic 
categories. This high percentage of endemicity agrees with 
what has been observed in other groups of organisms. 
Stewart® cites 615 species of plants from the archipelago, 
with 252, or 40.9%, endemic. Among the birds, according 
to Ridgway®, 13.04% of the 46 genera are endemic; among 
the Arachnida, according to. Banks’, 31, or 57.4% of the 54 
species are endemic; among the Orthoptera, according to 
McNeill® and Snodgrass*®, and among the Coleoptera cited 
by Linell’®, the percentage of endemicity is also very high, 
-although the authors do not give precise percentages. 
Many writers have noticed closer affinities between the 
Galapagos and Central American or West Indian species 
than between those of the Galapagos and the western coast 
5 Stewart, Alban. A Botanical Survey of the Galapagos Islands. Expedition of 
the California pcan of Sciences to the Galapagos Islands, 1905-1906. II. Proc. 
Calif. Acad. Sci. (4) 1, 1911, pp. 7-288, 18 pls. 
6 Ridgway, Robert. Birds of the Galapagos Archipelago. Proc. U. S. Nat. Mus. 
19, 1896, pp. 459-670, 2 pls. 
™Banks, Nathan. Arachnida. Papers from the Hopkins-Stanford Galapagos Ex- 
pedition 1898-1899, VII. Entomological Results (6). Proc. Wash. Acad. Sci. 4, 
1902, pp. 49-86, 3 pls. 
8 McNeill, Jerome. Orthoptera. Papers from the Hopkins-Stanford Galapagos 
Expedition 1898-1899, IV. REtemolonical Results (4). Proc. Wash. Acad. Sci. 3, 
1901, pp. 487-506, 10 figs. 
9 Snodgrass, R. E. Schistocerca, Sphingonotus and Halmenus. Papers from the 
Hopkins Stanford Gear ee Expedition. 1898-1899, VIII, Entomological Results (7). 
Proc. Wash. Acad. Sci. 4, 1902, pp. 411-455, 2 pls. 
10 Tinell, M. L. On the Coleopterous Tngects of the Galapagos Islands: Proc. 
U. S. Nat. Mus. 21, 1898, pp. 249-268. 
