280 ANTS. 



single exception of the Honda harvester (P. had ins), all of these 

 ants are confined to the dry plains and deserts of the Western and 

 Southwestern State.-, where, just as in the deserts of the Old World, 

 insect food is -carce. at least during many months of the year. 



Of the five species of Messor, M. pcryandei, carbonarius, andrei, 

 jnliaims and studdardi, which are confined to the extreme southwestern 

 portion of the t'nited States and northwestern Mexico, I have been 

 able to study only the first in a living condition. It is a shining, jet- 

 black ant of moderate size, very common in the deserts of southern 

 Arizona and the Mojave Desert of California. The workers, which 

 form populous colonies, vary much in the size of the body and the head, 

 like the Mediterranean M. barbarus. The nests (Figs. 152-154) are 

 single or more rarely mtdtiple craters, much flattened, with rounded 

 slopes, 50 cm. or more in diameter, and with one to three large and very 

 irregular central openings. Sometimes these are slit-shaped and as 

 much as 5 or 6 cm. long. The rough galleries and granaries are ex- 

 cavated to a depth of at least 60 cm. in the hardest and most sunbaked 

 portions of the desert soil. Late in the afternoon long files of workers 

 may be seen in the full activity of harvesting. Sometimes these files 

 may be followed for a distance of 20 or 30 m. from the nest before, the 

 ants disperse among the scant vegetation in search of seeds. They seem to 

 have no preferences, but eagerly seize all the mature seeds they find and 

 carry them to the nest, where they carefully remove the husks and store 

 the edible kernels in the granaries. The chaff and seed-pods are then' 

 carried out and dumped on the kitchen midden which forms a crescen- 

 tric or circular zone at the periphery of the crater. Sound seeds are 

 often thrown out with the chaff and eventually germinate, so that old 

 nests are often marked by a circlet of growing plants, just as Moggridge 

 has described for the European -pecies. There can be little doubt that 

 the other North American species of Messor have very similar habits. 

 A number of alcoholic specimens of one of these, .17. andrei. sent me 

 by Professor H. Heath from California, still bear grass-seeds in their 

 clenched mandibles. 



One of our two species of Ischnoin\nnc.r, I. cockerelli (Fig. 155 ) is 

 widely distributed over the deserts of western Texas, southern New 

 Mexico and Arizona and northern Mexico from an altitude of 2,500 feet 

 in the northern portion of its range (at Monahans, Texas) to 7,000 feet 

 on the Mexican plateau. The other species, /. albisctosns, seems to be 

 a rarer ant of more circumscribed distribution. At Fort Davis, Texas, 

 both species were found nesting side by side, so that I was able to 

 compare their habits. /. cockerelli is a large, very slender, long-legged 

 ant of a deep cherry-red color, with jet black gaster adorned with a 



