Conspecific presence increases the attractiveness of visual targets to host-seeking stable flies, Stomoxys calcitrans

The ‘friend factor’ describes the phenomenon that the presence of flies on a foraging site increases its attractiveness to conspecific flies. Stable flies, Stomoxys calcitrans, obtain one to two blood meals per day from a bovine host. Spending only short periods of time on-host, stable flies rest most of the time on a variety of perching sites that facilitate thermoregulatory behaviour and interactions with prospective mates. The presence of conspecifics on host animals may signify host suitability as a feeding site. However, according to a previous field study, captured flies on white sticky traps reportedly render traps less attractive to foraging flies. Our objective was to determine whether, or not, this off-putting effect is context dependent. In two-choice bioassays, we tested the response of starved female stable flies to black targets with or without the presence of conspecific females. Preliminary data indicate a strong preference towards visual targets with conspecific flies being present. Further rigorous testing of this phenomenon was underway at the time when abstract submission was due.