The koinobiont parasitoid Halticoptera circulus (Walker) is a potential biological control agent of leafminers, but it has only rarely been collected from the invasive leafminer, Liriomyza trifolii (Burgess), in Japan. To understand why this is the case, parasitism and development of H. circulus in L. trifolii was compared with parasitism and development in two indigenous leafminer species, Liriomyza chinensis Kato and Chromatomyia horticola (Goureau). There was no significant difference in parasitism rates by H. circulus in the three leafminer species and the eggs and larvae successfully developed in L. chinensis and C. horticola. However, H. circulus failed to develop in L. trifolii, where developmental stages were encapsulated by host haemocytes. This parasitoid may be a good agent to control indigenous leafminers such as L. chinensis and C. horticola but is unlikely to be useful for the biological control of the invasive L. trifolii in Japan.

Studies on developmental biology and feeding and ovipositional preferences of the pea leaf miner, Chromatomyia horticola (Goureau), were carried out on 11 varieties of field peas, Pisum sativum L. Two varieties, P-200 and P-402, offered maximum resistance to the development of pea leaf miner by inhibiting growth as both larval and puparial development were prolonged, and adult longevity, survival and fecundity reduced. These varieties were also least preferred for feeding and oviposition. Differences between the moderately resistant HFP-4 and highly susceptible varieties HFP-5, HFP-6, HFP-12, PG-3, RAU-21, RAU-25, RAU-37and T-163 were not well marked, as most of these had a relatively high value for the developmental success index, based on indices for larval-puparial development, adult longevity, survival and fecundity, and were also highly preferred by the ovipositing females. Variety PG-3, though offering some resistance to development, was highly preferred for oviposition. The local variety T-163, was the most susceptible variety, as it had the maximum value for the developmental success index, and was highly preferred by ovipositing females. The physiological basis of resistance in the two pea varieties is suggested to be mainly non-preference and antibiosis.