Diversity and foraging behaviour of floral visitors assemblages in onion Allium cepa L.

Anthophilous insects are of key importance for onion reproduction due to the protandrous nature of flowers, related to inbreeding avoidance. We documented the diversity of floral visiting insects on onion flowers at the ICAR-Indian Institute of Horticultural Research, Bengaluru, Karnataka, India, during 2019-21. The pollinator community is composed of thirty hymenopteran species, sixteen dipteran species, eight lepidopteran species, four hemipteran species, and one species from Coleoptera. From these, Hymenoptera and Diptera contributed >75% of the floral visitors. The majority of the floral visits by the anthophilous insects were for collecting nectar (81.59%) followed by nectar as well as pollen foraging (9.97%) and only pollen (8.44%). The proportion of stigma contact did not depend on the body size of the floral visitor. However, stigma contact depends on whether floral visitors collected nectar or pollen and also on the head width of the floral visitor. The present study helps to understand the pollination efficiency of pollination candidates for onion. Further, there is a need to study the pollen harvest and effective stigmatic pollen deposition by the floral visitors.