We studied the calling patterns of common true katydids (Pterophylla camellifolia) from sound recordings made during August through October 2007 in an oak-hickory forest in western Maryland. Nightly patterns of calling frequency were determined using 1-s samples spaced five min apart. The relationship between calling frequency (i.e., the number of twelve 1-second samples per hour in which singing occurred) and time of night, date, and weather variables, was modeled using logistic regression. Model predictability was high (73% of variance explained), with temperature and two rainfall-related variables having the most influence on calling frequency. This species of katydid exhibits a highly predictable degree of consistency in calling frequency, and consequently is well suited for use in ecological, distributional and status surveys.