The Male Drumming Call of Isoperla nevada Aubert , 1952 ( Plecoptera , Perlodidae )

The male drumming call of Isoperla nevada is described for the first time. The call is composed of a variable number (mode = 3) of diphasic sequences. The first sequence is longer, and contains more beats than the following ones. The number of beats per second increases during phase I of each sequence. The time between phases is less than 0.03 seconds while the time between two sequences varies from 0.13 to 0.24 seconds. The call of I. nevada differs from the morphologically similar species I. grammatica (Poda, 1761), whose call has been previously studied by other authors. The call of I. nevada contains fewer diphasic sequences than I. grammatica and its first sequence is different from the following ones, while all of the sequences of I. grammatica are similar. These behavioural characters support the separation of both species. The male mating call of I. nevada can be considered to be a derived pattern of drumming, and one of the most complex known in Isoperla.