Behavioural response of a parasitoid shows the effect on host parasitism
patterns at a given host distribution resulting in an increase or
decrease of parasitism intensity according to local host densities. This
relationship could be proportional, positive, or negative, as a
consequence of foraging of parasitoids searching for hosts. Mallophora
ruficauda is a fly parasitoid of Cyclocephala signaticollis scarab
beetle larvae and a predator of honeybees. Females search and place
egg-clusters overground in open grasslands near beehives. Larvae
actively searching for host underground following chemical cues arising
from the host itself. The parasitism pattern is a result of this complex
host-searching strategy which is shared between both stages of the fly.
In this work we carried out a study at four spatial scales in apiaries
located in the Pampas region of Argentina. We found that parasitism is
inverse density-dependent at high female activity and direct
density-dependent at low female activity at the larger spatial scale. We
found a direct density dependent pattern associated to substrate height
at intermediate spatial scale that is lost when the habitat has abundant
oviposition substrates. Conversely, parasitism is inversely
density-dependent at both smaller spatial scales, associated to
oviposition substrate distance and saturation of healthy host by larvae
attacking. We also found that M. ruficauda do not selects the
oviposition substrates according to the abundance of Cyclocephala
signaticollis inhabiting underground. We discuss the implications of
host searching behaviour on the observed parasitism patterns.