Body size of polyphagous parasitoids of agromyzid leafminers directly depends on that of their hosts. The possible influence of plant host on parasitoid body size was studied for the pea leafminer, Liriomyza huidobrensis Blanchard, and three of its most abundant solitary parasitoids: Phaedrotoma scabriventris (Nixon) (Braconidae), Halticoptera helioponi De Santis (Pteromalidae), and Chrysocharis flacilla (Walker) (Eulophidae) on 12 plant species. The relationship between host and parasitoid sizes was also examined to determine whether parasitoids use a consistent proportion of the host or whether different host plants allow varying degrees of resource exploitation. Significant differences were found in L. huidobrensis wing length, as well as in body and wing length of all parasitoid species studied, depending on the plant where the leafmining larvae had fed. Female parasitoid and host sizes were highly correlated. Despite leafminers attaining large body size, the host exploitation rate was consistently lower on Beta vulgaris cycla L., suggesting that plant aspects other than those determining leafminer size could be impairing host suitability on this plant. Within the range of plant hosts considered, Vicia faba L. would be the most adequate for rearing L. huidobrensis and the three parasitoid species studied, providing large individuals and an efficient biomass exploitation. none