Sexual dialogue in Pachyloides thorellii (Opiliones: Gonyleptidae): a Neotropical harvestman with much to say

Abstract. Describing the signals involved in sexual interactions is crucial to understand how mating and fertilization success is achieved. We analyzed sexual interactions in the gonyleptid harvestman Pachyloides thorellii Holmberg, 1878 to test the possibility of associations between female and male behaviors. For that purpose, we recorded 21 sexual interactions of P. thorellii under laboratory conditions and performed fine scaled analyses of the videos. We found three female pre-copulatory behaviors (“Mouth parts protrusion,” “Genital operculum opening,” and “Ovipositor eversion”) that seem to be related to sexual receptivity and cooperation with mating occurrence, and four copulatory behaviors (“Bucking,” “Pulling,” “Body lowering,” and “Leg II movements”) that could be indicating to the male that further stimulation is required or that mating is about to end. We also found that males use multimodal courtship displays that include the exchange of tactile and possibly chemical signals between sexes. This study shows that courtship and copulation in P. thorellii include intense information flow between sexes and female evaluation from the beginning until the end of the sexual interaction.