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Many ants and hemipterans are bound by a mutualistic relationship (trophobiosis) which represents an ecological keystone: ants receive food (honeydew) providing different kinds of protection. Partner protection against arthropod natural enemies is considered to be frequent and to interfere with biological control strategies of hemipteran pests.We carried out an ant‐exclusion field experiment in a fava bean (Vicia faba) plantation in Italy to monitor the abundance and behaviour of the ants (Plagiolepis pygmaea, Tetramorium semilaeve and the exotic Nylanderia jaegerskioeldi) and their relationship with facultative mutualist (Aphis fabae) and non‐mutualist (Megoura viciae) aphids, the arthropod natural enemies of the aphids, and extrafloral nectaries.Ants concentrated their activity on the attendance of facultative mutualist aphids much more than on the extrafloral nectaries. The ant‐exclusion treatment had no effect on the abundance of M. viciae and on the parasitization rate of A. fabae, while it reduced the abundance of A. fabae, aphid predators, and aphid parasitoids.Our results demonstrate that ant attendance does not imply the protection of aphids from arthropod natural enemies and suggest that the identity of the ant species involved is important for the outcome. As relatively few species have been studied in this regard, extending our knowledge to the role of more ant species is desirable to understand the ecology and evolution of ant‐aphid mutualisms and to refine integrated control strategies of aphid pests. [ABSTRACT FROM AUTHOR]

Bumblebees are opportunistic resource consumers and have been known to visit extrafloral nectaries and harvest aphid and scale honeydew. We report the first observation of bumblebees foraging psyllid honeydew in a tritrophic system in the boreal forest of Yukon Territory, Canada.In this system, a willow (Salix alaxensis) develops bizarrely enlarged petiole bases which act as nursery cavities for large numbers of psyllid immatures of Cacopsylla macleani (Homoptera: Psyllidae), with later instars dispersing over the underside of the leaf.These immatures produced abundant honeydew which was vigorously and persistently foraged by several bumblebees of multiple species (we identified Bombus vancouverensis, Bombus melanopygus and Bombus mckayi). Ants and vespid wasps were also present but in lower numbers.Salix alaxensis and Salix‐feeding psyllids are common throughout arctic and boreal regions, so honeydew production is potentially a supplementary food source for Bombus when floral nectar flows are limited due to low temperatures or drought. [ABSTRACT FROM AUTHOR]