Tri-trophic interactions of Blepharoneura diva (Diptera: Tephritidae) infesting male flower buds of Cucurbita argyrosperma , and its unusual parasitism by the wasp Opius hirtus (Hymenoptera: Braconidae)

SummaryTri-trophic plant-insect-parasitoid interactions are one of major mechanisms of phytophagous diversification and niche exploitation. The flies of the genus Blepharoneura Loew, 1873 are highly specialised, feeding exclusively on plants of the family Cucurbitaceae. The pumpkin Cucurbita argyrosperma C. Huber, 1867, locally known as ‘calabaza pipiana’ is cultivated for seed consumption in several regions of Mexico, sometimes coexisting with a wild subspecies C. argyrosperma subsp. sororia (L. H. Bailey, 1943) Merrick & D. M. Bates, 1989, considered the ancestor of the domesticated plants. In this paper we assessed the infestation rates of Blepharoneura diva Giglio-Tos, 1893 on flower buds of ‘calabaza pipiana’, from both crops and wild plants over an annual flowering cycle between July and October 2021. The results showed that B. diva infested only male flower buds of cultivated plants, while it was absent from wild flowers. A significant increase in infestation rates (63.1%) was observed towards the end of the flowering season in early September, which correlated with an increase in the average size of the flower buds. In addition, the wasp Opius (Bellopius) hirtus Fischer, 1963 (Hymenoptera: Braconidae) was recorded for the first time parasitising larvae of the genus Blepharoneura, accounting for 37.2% of the viable pupae sampled. This is the first report of the tri-trophic interaction B. diva–C. argyrosperma–O. hirtus, revealing that this is a stenophagous fly specialised on male flower buds of the genus Cucurbita L., 1753. Domestication processes of C. argyrosperma probably influenced the host choice of the fly, which preferentially feeds on cultivated flower buds rather than wild plants. Historical background on the biology of this parasitoid wasp revealed that it only attacks the fruit-feeding larvae of several tropical tephritid species. Therefore, our results revealed a significant shift in the ecology of the wasp, to parasitise flower-feeding larvae of cucurbits.