Differences in growth and development of the parasitoids Dacnusa nipponica and D. sibirica (Hymenoptera: Braconidae) on the leaf-mining fly Liriomyza trifolii (Diptera: Agromyzidae) compared to various-sized leaf-mining Chromatomyia horticola hosts (Diptera: Agromyzidae)

The indigenous endoparasitic koinobiont Dacnusa nipponica is considered a potential parasitoid of the exotic leaf-mining fly Liriomyza trifolii in Japan. However, this endoparasitoid rarely emerges from L. trifolii pupae collected in the field. To determine why, we compared the parasitization, growth, and development of D. nipponica and the introduced parasitoid, D. sibirica, on L. trifolii hosts. When each parasitoid was only provided L. trifolii as a host, D. nipponica exhibited a slightly lower parasitization rate (confirmed by dissecting hosts, 34.7%) than D. sibirica (42.2%). However, the survival rate of parasitoid progeny within hosts was much lower for D. nipponica (7.2%) than for D. sibirica (69.4%), which was caused by the developmental arrest or death of D. nipponica at the prepupal stage within L. trifolii pupae. Furthermore, the survival rate of parasitoid progeny within hosts was much lower for D. nipponica (13.3%) than for D. sibirica (82.6%) when both parasitoids were allowed to parasitize artificially dwarfed individuals of Chromatomyia horticola, which is naturally much larger than L. trifolii and is a suitable host for both parasitoid species. The survival rate of progeny was lower for both D. nipponica and D. sibirica within smaller individuals of dwarfed C. horticola pupae. These results suggest that L. trifolii is large enough to host the growth and development of D. sibirica but too small for successful parasitization by D. nipponica.