4 Bulletin American Museum of Natural History. [Vol. XXIII, 



The acme of the colonial activities of Ph. instabilis is attained during 

 the latter part of May and the first weeks of June. Then the nest is full 

 of eggs, larvfe, pupae, and callows of all the castes and presents a bewildering 

 appearance, owing to the fact that the brood is not assorted according to 

 ages, as in many ants, but lies jumbled together in the different chambers 

 and galleries. The functions of the workers and soldiers are clearly dis- 

 tinct. The former are far and away the more numerous, and notwithstand- 

 ing their diminutive size, may be said to manage the affairs of the colony. 

 They collect the seeds and dead insects and drag them to the nest. They 

 excavate the galleries, feed the brood and carry even the huge female larvae 

 and pupae from chamber to chamber and assist the callows in escaping from 

 their pupal envelopes. The soldiers act as carvers, or trenchers of the 

 tough insects and hard seeds brought in by the workers. Their powerful 

 mandibles admirably fit them for this office and for guarding the nest. 

 They are often seen to form a stationary cordon about the brood and the 

 callows in the chambers. They are never seen to eat the seeds or insects 

 which they cut up for the other members of the colony but are fed on liquid 

 food regurgitated by the workers. They are very stolid and inactive, very 

 rarely leave the nest and never assist in carrying the larvae and pupae about. 

 Their heads are so large in proportion to their bodies that, when dropped 

 on their backs on a smooth surface like that of glass or polished wood, they 

 are often unable to right themselves and may die standing on their heads. 

 The intermediates are much more active and may be seen to leave the nest, 

 collect food, carry larvae and, in short, perform all the duties of the workers 

 which they approach in their smaller size and smoother sculpture. 



The larvae of all the castes are provided with several pairs of flexuous, 

 anchor-tipped dorsal hairs, by means of which they may be temporarily fixed 

 to the earthern walls of the chambers or to the rough surfaces of the stone 

 covering the nest. While in this position they are fed by the workers with 

 bits of crushed seeds or insect fragments in the same way as the larvae of the 

 Ponerine ants. At least the younger larvae of the males and females, how- 

 ever, appear to be fed largely, if not exclusively, with regurgitated liquid 

 food. 



Ph. instabilis is very common at Austin in the bottom and along the 

 banks of a small limestone caiion, known as Shoal Creek. There, during 

 May and June, 1903, I found a great number of colonies. Several of them 

 were confined in artificial nests of the Fielde pattern and one was kept 

 under observation till the latter part of September. I also preserved whole 

 colonies in alcohol after killing them in water heated to 80° C. 



Fully half of the colonies examined were found to contain the peculiar 

 parasites which Dr. W. H. Ashmead has kindly identified for me as Orasema 



