Male attraction to female airborne cues by the net-casting spider, Deinopis spinosa.

For many animals, finding a mate can be a difficult task. For males, it often involves actively searching for conspecific females, sometimes over great distances. This mate-searching can be aided through chemical or visual signals or cues produced by sexually receptive females. Here, we investigate the roles of olfaction and vision in mate-searching in a strictly nocturnal net-casting spider, Deinopis spinosa. First, we used an olfactometer assay to determine if mature male D. spinosa respond to conspecific airborne cues. We found that mature males, but not mature females, were attracted to airborne cues of mature female conspecifics. We next investigated the relative importance of olfaction and vision in male mate-searching. While manipulating airflow and light levels in screened enclosures in the laboratory, we tested freely moving mature males for mate-searching success. We found no effect of our airflow treatment on mate-searching success. Light levels, however, affected mate-searching in an unexpected way - males were more likely to locate females in complete darkness when compared to dim-light conditions. Our results suggest that visual cues are not necessary for successful male mate-searching in D. spinosa, but that the visual environment can nonetheless influence male behavior. In summary, we provide evidence suggesting that airborne cues, but not visual cues, are important in D. spinosa male mate-searching efforts, though the source of these chemical airborne cues remains unknown.