DROSOPHILA PERCNOSOMA HARDY LEK SITES - SPATIAL AND TEMPORAL DISTRIBUTIONS OF MALES AND THE DYNAMICS OF THEIR AGONISTIC BEHAVIOR (DIPTERA, DROSOPHILIDAE)

Drosophila percnosoma form leks and defend leaves on isolated trees (C lermontia) in the Hawaiian rainforest. Males do not prefer lower leaf groups, but more male-male agonistic interactions take place on the lo wer leaf groups, suggesting that they may be preferred by the most agg ressive males. D. percnosoma males show diurnal variation at leks. The time of peak abundance was 1000 to 1300 hr, with numbers declining at 1500 hr. Male removal resulted in rapid occupation of previously occu pied leaves. Agonistic interactions occurred non-randomly among the 15 leaves that were monitored, with larger leaves or particular leaves i n a given leaf group being preferred. Males that win agonistic interac tions are usually either the larger or the resident or both. An intera ction begins when an intruder lands on an occupied leaf. Intruders may decamp early if the resident is much larger. If the intruder remains after landing, the agonistic interaction escalates to either wing flic ks by the resident or to a side-to-side pushing match. Two males may c ome together, oriented head-to-head, and then rear up anteriorly and ' 'box'' with the front legs. This may be followed by mutual wing-raisin g, and assumption of a side-to-side posture (each facing in a differen t direction) with wings still extended. In this posture the flies appe ar to push laterally, often toward the leaf margin. At any point eithe r male may decamp.