242 THE BIOLOGY OF INSECTS 



insects' abdomens become capable of considerable dis- 

 tension. This condition is brought to extreme development 

 by the oft-described Mexican honey-ants (Myrmecocystus)^ 

 in the underground chambers of whose nests special workers 

 with immensely swollen abdomens may be found hanging 

 from the roof by their feet, back downwards. These 

 bloated creatures (" repletes ") incapable of movement, 

 are fed by the foraging ants in order that they may serve as 

 " honey-pots " for the community as a whole. The 

 abdomen of a replete assumes approximately a globular 

 form, the pale intersegmental cuticle becoming greatly 

 expanded and the normal dark abdominal sclerites appearing 

 on its area as narrow transverse bars. H. McCook (1882), 

 who first carefully investigated the nests of these honey- ants, 

 believed that the repletes are workers definitely adapted 

 for their strange function by the structure and character 

 of their abdominal cuticle and the wall of their food-canal. 

 Wheeler, however, considers that there is no inherited 

 difference between the foraging and the honey-pot workers ; 

 the latter are modified if they assume the part of reservoirs 

 when sufficiently young, while their tissues are still plastic, 

 but *' thoroughly hardened workers of the ordinary form 

 . . . are no longer able to become repletes." 



The most specialised form of behaviour among ants 

 that feed on vegetable substances is probably exhibited by 

 the fungus-gardeners (Atta) already mentioned in this 

 chapter (p. 239). The harvesting ants, however, whose 

 activities are celebrated in the writings of Hebrew sages 

 and Greek and Roman poets, display purposive habits 

 hardly less surprising. The ancient accounts of these 

 insects were indeed regarded with no little doubt until 

 the careful observations of T. C. Jerdon (1854) on Indian 

 species of Pheidole and SolenopsiSy and of T. J. Moggridge 

 (1873) on the South European Messor harharus and allied 

 forms, convinced naturalists that the workers of these ants 

 do indeed collect the seeds of plants suitable for food and 

 store them in the underground chambers of their nests. 

 Germination of the harvested grain is prevented by the ants 



