Walker summarized the diel patterns of calling in the singing Orthoptera. A number of social, ecological and environmental factors influence the daily rythms in calling. For mole crickets (Scapteriscus, upper left panel), two species differ slightly in their calling periods. Both species call for about 1 hours shortly after sunset, but S. vicinus begins and ends earlier in the evening (dotted line) compared to S. borellii (solid line). Male short-tailed crickets, Anurogryllus arboreus (lower left panel) also call for a brief period near sunset. Male arboreus that call from perches (dotted line) begin calling before and end later than those males calling from the entrances of their burrows (blue line). Another short-tailed cricket from Panama, A. muticus (upper right panel), can be heard calling at all hours of the night. Only about 20-30% of the males call at any one time. Male muticus calling near their burrows stop calling in the middle of the night, whereas wandering males call throughout the night. The diel calling patterns of field crickets, Gryllus (lower right panel), can depend on population density. Under low density conditions there is a peak of calling after sunset followed by a waning of activity throughout the night with a second peak of calling just before sunrise. The early evening peak is diminished when the populations are at high density.