Low humidity as a cue for habitat preference in the parasitoid Lariophagus distinguendus

The larval and pupal parasitoid Lariophagus distinguendusFörster (Pteromalidae) is a potentialcandidate for the biological control of thegranary weevil Sitophilus granarius L.and other stored product pests that mostlyprefer the dry conditions of a storageenvironment. To predict whether parasitoidswill remain within the dry storage environmentafter release, experiments with L.distinguendus were performed in a humiditygradient chamber. To our knowledge, this is thefirst time that humidity preference wasexamined directly for a parasitoid species.Regardless of experience, parasitoidssignificantly preferred drier areas in theorder 32.5% (most preferred), 53%, 75.5%,and 97.5% r.h. (least preferred). Thisindicates that humidity is used as cue for hosthabitat preference. When used as natural enemyagainst stored product pests this preferenceprobably will retain L. distinguenduswithin the storage environment after theirrelease.