none no species Populations of immature Ancyloxypha numitor (F.) were monitored in 1979 and 1981 on three dwarf (60 to 75 cm) and three tall (118 to 122 cm) cultivars of rice. Significant (P < 0.05) differences in the number of A. numitor larvae per 100 tillers (1979) and the number of eggs, larvae, and total immatures per 100 tillers (1981) were noted between dwarf and tall cultivars. The hymenopterous parasites Agathis n. sp., Pediobus n. sp., and Elachertus n. sp. were recoverd from infested A. numitor larvae. Overall, A. numitor parasitism varied from 3.7 to 48.0%. Agathis n. sp. was the dominant parasite, comprising from 72 to 100% of the total parasite population. The increased A. numitor immature populations and defoliation on the dwarf rice cultivars evaluated here suggest the need for identification and development of dwarf cultivars with A. numitor resistance. Nutrition; Diet; Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts; Host parasite relationships; Ecology; Population dynamics; Land and freshwater zones; Nearctic region; North America; USA Ancyloxypha numitor (Hesperiidae); Food plants; Oryza sativa (rice); Cultivar height effect on density; Hymenopteran parasites; Elachertus & Pediobus; Prevalence; Agathis; Elachertus & Pediobus (Hymenoptera) parasites; Population density; Food plant height relationship; Louisiana; Food plant height effects on density & hymenopteran parasites prevalence Agathis (Braconidae ); Elachertus; Pediobus (Eulophidae ); Lepidopteran hosts; Ancyloxypha numitor; Prevalence; Ancyloxypha numitor (Lepidoptera) host; Louisiana; Prevalence in lepidopteran host