Cleptoparasitism, also known as brood parasitism, is a widespread strategy among bee species in which the parasite lays eggs into the nests of the host species. Even though this behavior has significant ecological implications for the dynamics of several species, little is known about the molecular pathways associated with cleptoparasitism. To shed some light on this issue, we used gene expression data to perform a comparative analysis between two solitary neotropical bees: Coelioxoides waltheriae, an obligate parasite, and their specific host Tetrapedia diversipes. We found that ortholog genes involved in signal transduction, sensory perception, learning, and memory formation were differentially expressed between the cleptoparasite and the host. We hypothesize that these genes and their associated molecular pathways are engaged in cleptoparasitism-related processes and, hence, are appealing subjects for further investigation into functional and evolutionary aspects of cleptoparasitism in bees.

Cleptoparasitic or cuckoo bees lay their eggs in nests of other bees, and the parasitic larvae feed the food that had been provided for the host larvae. Nothing is known about the specific signals used by the cuckoo bees for host nest finding, but previous studies have shown that olfactory cues originating from the host bee alone, or the host bee and the larval provision are essential. Here, I compared by using gas chromatography coupled to electroantennographic detection (GC-EAD) the antennal responses of the oligolectic oil-bee Macropis fulvipes and their cleptoparasite, Epeoloides coecutiens, to dynamic headspace scent samples of Lysimachia punctata, a pollen and oil host of Macropis. Both bee species respond to some scent compounds emitted by L. punctata, and two compounds, which were also found in scent samples collected from a Macropis nest entrance, elicited clear signals in the antennae of both species. These compounds may not only play a role for host plant detection by Macropis, but also for host nest detection by Epeoloides. I hypothesise that oligolectic bees and their cleptoparasites use the same compounds for host plant and host nest detection, respectively.