Rythmes d'activit\'e locomotrice chez deux insectes parasito\"ides sympatriques : Eupelmus orientalis et Eupelmus vuilleti (Hym\'enopt\`ere, Eupelmidae)

TL;DR

This study used automatic image analysis to compare the daily locomotor activity rhythms of two parasitoid wasp species, revealing a temporal shift that likely reduces their competition in shared habitats.

Contribution

It provides new insights into the activity timing differences between Eupelmus orientalis and Eupelmus vuilleti, highlighting how temporal separation may facilitate coexistence.

Findings

Both species show daily activity cycles with activity mainly during the day.

E. vuilleti starts activity 4-5 hours earlier than E. orientalis.

E. vuilleti begins activity before light onset, E. orientalis only in light.

Abstract

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.