  With an automatic image analysis device, we studied the temporal distribution
of the locomotor activity of E. orientalis and E. vuilleti during 24 h, and
over several days to know whether the activity rhythms of these two Eupelmidae
play a role in their competitive interactions. The analysis of locomotor
activity rhythms of E. orientalis and E. vuilleti shows that the locomotor
activity of both species presents daily cyclic variations. These two Eupelmidae
have similar activity rhythms. Displacements of these parasitoids essentially
take place during the photophase. But the activity of E. vuilleti is earlier,
because the individuals of this species start their activity on average 4 to 5
h earlier than those of E. orientalis. E. vuilleti begins its displacements
several hours before the onset of lighting, whereas E. orientalis is active
only in the presence of the light. This shift of starting activity is thus a
factor allowing these concurrent species to minimize their interactions during
the cohabitation period in traditional granaries after the harvests of cowpea.
