Novel associations in antibiosis stemming from an insect pupal cell

•Novel antibiosis was confirmed in pupal soil cells of three curculionids.•Antibiosis occurred against both insect and plant pathogenic fungi.•Antibiosis was suspected to originate from inside the insect in the soil cell.•Antibiosis in Curculio caryae was associated with a bacterium related to Serratia nematodiphila.•Antibiotics from pupal soil cells may be developed as novel bio-fungicides.