Standardized chrysanthemum plants,Chrysanthemum morifoliumRamat, were exposed to selected numbers of ovipositing adult femaleLiriomyza trifolii(Burgess) (Diptera: Agromyzidae) to analyze thc effects of intraspecific competition on the survivorship of larvae and quality of emergent adults. The effect of intraspecific competition on the ratio of emergent pupae to newly eclosed larvae (P:L ratio) and pupal size was determined. Pupal size was found to be a positive indicator of longevity and oviposition of adults. The P:L ratio was inversely related to intraspecific competition and ranged from 0 (severe competition) to 1.0 (no competition). Smaller pupae were obtained from plants with low P:L ratios. A maximum of 30 larvae could complete development in a standardized chrysanthemum plant without adversely affecting the P:L ratio.