ThreeApium graveolens(L.) varieties and cultivars within varieties were evaluated for host plant suitability to two polyphagous lepidopteran herbivores: the beet armyworm,Spodoptera exigua(Hübner), and the cabbage looper,Trichoplusia ni(Hübner). Overall, there were no significant differences in survivorship, developmental time, and pupal weight ofS. exiguaorT. nireared on the two varietiesA. graveolensvar.dulceandA. graveolensvar.rapaceum. Intravarietal differences did exist between cultivars ofA. graveolensvar.rapaceum; S.exiguareared on ‘Kockanski’ had a significantly lower mean survivorship to pupation (27.5 versus 82.5%), a significantly longer mean time to pupation (18.5 versus 13.7 d), and a significantly lower mean pupal weight (37.6 versus 75.0 mg) thanS. exiguareared on ‘PI 223333’, a different cultivar ofA. graveolensvar.rapaceum. In contrast to the response ofS. exigua, there were no significant differences in the life history variables amongT. nireared on the same cultivars ofA. graveolensvar.rapaceum.Quantitative nutritional analysis showed that the differential response ofS. exiguaandT. nito the twoA. graveolensvar.rapaceumcultivars was caused by inability ofS. exiguato compensate for reduced efficiencies of conversion of ‘Kockanski’ to larval biomass. Variation in total nitrogen contents were not responsible for the observed variation in compensatory abilities.