1905.] Wheeler, Ants of the Genus Liometopum. 331 



server to believe that he has found the nest, but these cavities contain 

 no larvae, males, or females, and careful inspection shows that they 

 lead off into a continuation of the runway. The cavities are, in fact, 

 mere temporary resting places for the out- and home-bound com- 

 panies of workers. 



It is, perhaps, easy to account for the difference in the nesting- 

 sites of the European and American species of Liometopum. when we 

 consider the great climatic differences between southern Europe and 

 the mountainous regions of southwestern North America. The pro- 

 tracted periods of drought in the latter regions make the decayed 

 wood of tree-trunks extremely undesirable abodes for moisture-loving 

 insects like the ants. They are therefore compelled to nest in the 

 soil and naturally seek places under stones where the moisture is 

 longest retained. 



If the observations of Emery and Forel can be accepted as final, 

 there is also another great ethological difference between the American 

 and European species of Liometopum, a difference relating to the 

 feeding habits. Mayr was of the opinion that L. microcephalum could 

 be climbing about on the trees only for the purpose of attending 

 aphides, but Emery claims that the ants merely devour these insects 

 and Forel speaks of their despising the plant-lice. Our American 

 species, however, is eminently aphidicolous and coccidicolous, al- 

 though, like microcephalum., it is always ready to feast on any cater- 

 pillars, beetles, etc., that may fall in its path. In the Paisano Pass 

 the files of apiculatum were frequently seen attending the aphides on 

 the leaves of two species of mountain oak (Quercus emoryi Torr. and 

 Q. undulata Torr.). At Ft. Davis I found thousands of these ants in 

 attendance on a lot of aphides that covered the flower spikes of some 

 large yuccas. Another colony was similarly engaged on the leaves 

 of willows and cedars. At Manitou similar observations were made. 

 Here they were also attending snow-white Coccidae on roots that ex- 

 tended across their dark runways. These ants love to collect the 

 nectar of flowers. In the Paisano Pass a colony was busy plundering 

 the blossoms of the cat's claw {Acacia wrightii Benth.). At Ft. 

 Davis I saw unmistakable evidence of their pronounced carnivorous 

 instincts. A file was dragging caterpillars to its nest and a mass of 

 ants were trying to get at the soft parts of a dead specimen of one of 

 our largest longicorn beetles (Derobrachus geminatus Lee), measuring 

 6.5 cm. in length. These diverse observations show the close re- 

 semblance in habits between the species of Liometopum in the western 

 and the species of Dolichoderus in the eastern states of the Union. 



