To obtain a bait composition excellent in the control of ants by making the composition include a fenitrothione microcapsule and boric acid as active ingredients and a hydrous gel as a base material.

This poisonous bait composition is obtained by blending (A) a fenitrothione microcapsule (e.g. a microcapsule formed by covering fenitrothione with a film of a polyurethan polymer or the like) and (B) boric acid as active ingredients and a hydrous gel (e.g. a gel formed by adding a gelatinizer such as agar or the like into water under heating, converting it into a liquid state and solidifying it under cooling) as a base material. It is favorable that the above composition contains the components A and B in amounts of 0.1-2 wt.% and 1-10 wt.%, respectively and the combination ratio between the components A and B is 1:1 to 1:10. Further, as the other component, a grain, e.g. wheat flour, corn flour or the like, and an oil, e.g. butter or the like, can be blended as an attraction-tasting agent.