NATURAL VARIATION IN THE TEMPORAL PATTERNING OF CALLING SONG STRUCTURE IN THE FIELD CRICKET GRYLLUS-PENNSYLVANICUS - EFFECTS OF TEMPERATURE, AGE, MASS, TIME OF DAY, AND NEAREST-NEIGHBOR

Genetic and environmental sources of variation in the temporal pattern ing of song structure may be important variables influencing male fiel d cricket reproductive success. Song structure in both field and labor atory populations of Gryllus pennsylvanicus was examined to assess pos sible sources of variation. Factors examined included temperature, mal e age, body mass, time of day, and male spacing patterns. Temperature was positively correlated with pulse rate and negatively correlated wi th interchirp interval for both field and laboratory populations. Temp erature was negatively correlated with chirp duration only in the fiel d population. Calling song structure did not vary with male age or mas s. Time of day had a significant effect on the song parameters examine d, even when data were corrected for temperature differences. Males ca lling in the morning had faster pulse rates and shorter chirp duration s than males recorded at night time. Male spacing patterns also influe nced calling; isolated males had longer intervals between consecutive chirps than clumped males. Data are discussed in terms of acoustical c ompetition between males and female choice.