This study was carried out to compare the host preference and oviposition behavior of T. petiolata in relation to different host plant species. Observations were made using stems of D. caespitosa contained in cages under laboratory conditions. Host plant preference was studied by introducing one adult T. petiolata female (4-5 days old) into a cylindrical cage containing four grass species including D. caespitosa, the natural host food plant. Female behavior was classified into five categories: grooming, resting, walking, searching, landing and oviposition. Walking and searching were distinguished by the attitude of the antennae. The mean time spent grooming and resting on each host food plant did not vary significantly between plants. In the oviposition choice experiments large number of larvae were reared from the host plant, but none were reared from other plants except for D. setacea, an unnatural host from which a few larvae were reared. This suggests that T. petiolata is at most potentially narrowly polyphagous and that females prefer one species much more than another. Since in the field, larvae of T. petiolata have never been recorded in the stems of D. setacea, the desposition of eggs in D. setacea can be regarded as a laboratory artifact and T. petiolata can be regarded as monophagous under natural conditions.