This study deals with preference of different seed particles of a novel type of foods by ants of the species Messor arenarius (Fabricius). Given choices between different wheat seed particles at the same distances from the nest, the first time wheat was offered to M. arenarius they reacted as follows: They preferred halves of wheat seeds cut longitudinally most significantly over whole-wheat seeds. Three-quartered of wheat seeds were preferred significantly over one-quartered wheat seeds. There was no preference in the choice between whole-wheat seeds and halves of wheat seeds cut transversely. From the second day and up to the fourth day when these choices were offered, the ants showed no preference in choice between whole-wheat seeds and halves of wheat seeds cut longitudinally. The preferences in the other choices were about the same as the first time that wheat was offered to the ants. The average returning time of ants to the nest with a whole-wheat seed did not differ significantly from that with a half seed cut longitudinally. From these findings, it seems that the first time wheat is offered to the ants, both the odor and the relative length of the food item are preference criteria used by the ants in their food choice.