No.422.] NEW AGRICULTURAL ANT FROM TEXAS. 97 
the least improbable that these ants, like the South-American species of 
Didelphys, deer, camelids, and mastodons, are of North-American origin. 
Without being able to adduce stringent proof in favor of my opinion, I 
nevertheless incline to accept this latter view. 
The migration between the continents is supposed to have 
taken place during the Pliocene. This view of the North- 
American origin of Pogonomyrmex is supported to some extent 
by the flourishing condition of the closely allied holarctic 
genera Myrmica and Stenamma (including the subgenera 
Aphzenogaster and Messor) in the United States and Canada. 
A problem of more subordinate interest is suggested by the 
close morphological relationship of the Brazilian P. negelii 
and the Texan P. imberbiculus, without known forms of a simi- 
lar aberrant character in the intervening geographical region. 
It is possible, how- 
ever, that a more 
searching  investiga- 
tion of the Mexican 
and West-Indian 
fauna may bring to 
light still other beard- 
less forms of Pogono- 
myrmex and thereby fill this gap. It should be mentioned, 
nevertheless, that the new Texan species has all the appearance 
of being a geological “ relict.” 
In conclusion I subjoin a dichotomic table to aid in the 
identification of the workers of the North-American species of 
Pogonomyrmex : | 

badius Latreille. Worker. 

Fic. 8. — P E Y 
I. Small species, less than 5 mm. long ; under surface of head without a 
beard of long cürved hairs; epinotum armed with four spines; head, 
thorax, and petiole coarsely reticulate rugose, base of gaster not 
striated. Formicary under stones. (Central Texas.) 
P. imberbiculus n. sp. 
2. Larger species, more than 5 mm. long; under surface of head with a 
beard of long, curved hairs; epinotum with only two spines or none; 
head and thorax finely rugose, the ruge being more or less parallel 
with one another, not reticulate. Formicary not under stones, 
exposed... ea oA ee LE NISL T 3 
3. Epinotum with a single pair of spines  . 
* - * 
ec] $ 
