Experiments were conducted on Mygalopsis marki Bailey to determine the response of calling males to singing intruders. By increasing the density of natural aggregations of singing males we were able to observe the behavioural responses of individuals. In high density situations, males sang from lower perches in their plant and this effect was correlated with each male's proximity to other calling males. Furthermore, to examine if resident males were affected by conspecific song, a playback technique was employed using tape recordings of M. marki song. The design of the experiment was such that when confronted with an intruder, steadily increasing the intensity of its song, resident males moved to a lower position in the plant and ceased singing.