A sex-specific tri-trophic-level effect in a phoretic association

Hemisarcoptes coccophagus (Acari: Astigmata: Hemisarcoptidae) is an obligate parasite of armored-scale insects (Homoptera: Diaspididae). Hypopodes (non-feeding heteromorphic deutonymphs) of this mite cannot complete their development without a phoretic sojourn on the coccinellid beetle Chilocorus bipustulatus. We tested whether the feeding history of the beetles affects the probability of the hypopodes completing their development. Two diets were offered: armored-scale insects (Homoptera: Diaspididae) (suitable for both beetles and mites) and soft-scale insects (Homoptera: Coccidae) (suitable for the beetles but not for the mites). The hypopodial survival was similar for mites which had been on beetles reared on the different scales. However, female hypopodes which had stayed on beetles reared on soft scales suffered higher mortality than those from Chilocorus reared on armored scales. Male survival was not affected. A tri-trophic-level effect on sex-specific survival in a phoretic association was thus demonstrated.