7.7.0 



SCIENCE. 



[N. B. Vol. XV. No. 38^. 



will also hold good to a considerable extent 

 of the social wasps and probably also oJ: 

 the termites. The colonies of the former, 

 however, are of annual instead of perennial 

 growth like those of ants and termites. 

 This is a difference of no little importance 

 from the standpoint of our discussion, since 

 it is readily seen that the conditions pre- 

 vailing among ants and termites must tend 

 to develop and strengthen the domesticating 

 instinct to an extraordinary extent. This 

 is indicated by the host of known myrme- 

 cophiles and termitophiles as contrasted 

 with the few guests and parasites known 

 to live in the nests of wasps. 



The dependence of variability on the age 

 and trophic status of the colony is most 

 clearly seen in ants that have polymorphic 

 workers. The huge, cosmopolitan genus 

 Pheidole, e. g., is particularly interesting 

 in this respect. Its species are character- 

 ized by having workers of at least two very 

 different aspects: minute, small-headed 

 workers proper, and huge-headed soldiers, 

 often of monstrous aspect. In a few Amer- 

 ican species (P. instabilis Emery, carion- 

 aria Pergande and vaslitii Pergande) these 

 two forms are connected in the same nest 

 by perfect series of intermediates. In the 

 vast majority of species, however, such 

 transitions are very rare or altogether 

 wanting. The queens of Pheidole are much, 

 the males but little, larger than the soldiers. 



The soldiers are put to different uses by 

 different species. In the grain-storing 



surrounded by five diminutive workers. While 

 it is certainly remarkable that one does not find 

 similar incipient colonies of our other Ponerinae, 

 this observation makes it probable nevertheless 

 that the ants of this subfamily agree with the 

 Componotinse, Myrmicinfe and Dolichoderinse in 

 their method of founding colonies. Concerning 

 the methods employed by the driver ants 

 (Dorylii) and ants of visitation (Ecitonii) noth- 

 ing is known. These remarkable insects are so 

 secretive in all that relates to their household 

 affairs that only time and lucky observation will 

 be able to fill this gap in our knowledge. 



species they function as the official seed- 

 crushers of the community. The diminu- 

 tive workers collect the seeds and store and 

 move them about in the chambers of the 

 nest. They are, however, quite unable to 

 break the hard shells, which yield only to 

 the powerful jaws of the soldiers. In the 

 carnivorous species the workers bring in 

 pieces of insects, while the soldiers act as 

 trenchers and sever the hard, chitinous 

 joints. In the above-mentioned American 

 species with polymorphic workers, I believe 

 that the transitional forms may also be of 

 use to the colony as seed-crushers and 

 trenchers, since the vegetable and animal 

 food is of different degrees of hardness and 

 the work of making it accessible is not 

 thrown on a single caste as it is in the 

 strictly dimorphic forms. In some species 

 the soldiers undoubtedly deserve their 

 name, for they run about with wide-open 

 mandibles and attack any intruder with 

 great fury. In other species they are very 

 timid and make for the concealed chambers 

 as soon as the nest is disturbed. They thus 

 ' manifest an instinct which is highly 

 developed in the sexual forms, especially 

 the queens, whom the soldiers also resemble 

 in certain morphological characters more 

 closely than they do the workers. 



Under ordinary conditions only the 

 workers of Pheidole go abroad, while the 

 soldiers remain at home and very rarely 

 stray beyond the entrance of the nest unless 

 the whole colony is moving to a new home.* 



* The Pheidole soldiers may leave the nest 

 when needed as trenchers to carve the carcass of 

 some insect that is too unwieldy to be dragged 

 home by the workers. I have observed this in two 

 of our smaller species, Ph. vinelandica Forel and 

 Ph. splendidula n. sp. (allied to Ph. metallescens 

 Emery). In the former ease a caterpillar had 

 fallen into a large ant-lion pit about three yards 

 from the nest and had evidently been killed and 

 partially consumed by the ant-lion. The carcass 

 was covered with workers and soldiers busily en- 

 gaged in cutting it into portable fragments. In 



