Bioacoustics of Okanagana georgi

Biological Notes. The species is associated with what Ku¨ chler (1964) calls chaparral. The chaparral in Arizona is a transition type vegetation between oakjuniper woodland and mountain mahogany-oak scrub. On Schnebly Hill, it interfingers with the juniper-pin˜ on woodland. The specimens of O. georgi have been collected primarily from Arizona cypress, Cupressus arizonica Greene , in a riparian habitat within the canyon. Additional specimens have been collected from alligator juniper, Juniperus deppeana Steud. ; scrub oak; and riparian trees. An aggregation was observed in the upper portions of a large Lowell ash, Fraxinus anomala variety lowelli [Sarg.]Little, in 2001, which quickly dispersed when a single individual was captured. Arizona Cypress seems to be the preferred plant for association and may be the host for the nymphal stages. The other plant species from which specimens were collected seem to be perching sites, because we have isolated references to the cicadas using these plants as perches rather than the repeated associations recorded between the cicadas and Arizona cypress. Calling Activity and Calling Song. Okanagana georgi were highly active between 10:30 a.m. and 2:00 p.m. and again late in the afternoon between 4:00 p.m. and 6:00 p.m. mountain standard time. Calling activity is regulated by the availability of solar radiation. Calling does not begin until the sun has been available to the animals for several hours, and calling activity ceases as the shadows fall over the canyon. These restrictions are probably the result of an inability to maintain the elevated body temperature necessary to coordinate calling as has been described in many cicada species (for reviews, see Sanborn 2002 , 2005 ). Similar acoustic behavior is exhibited by the sympatric species of Okanagana along Schnbly Hill Road. The cicadas were observed in both juniper and ash calling from the leaves instead of the branches or trunks. The call is a continuous train of sound pulses without frequency or amplitude modulation. The sound pulses are produced at a rate of 106.92 ± 1.331 Hz ( n = 10 segments of the single call recorded). The alarm call has an average peak intensity of 97.4 dB ( n = 1) at 50 cm (2 X 10 ¯4 dynes cm ¯2 ). The intensity of the O. georgi call does not differ from what would be predicted based on the size relationship described by Sanborn and Phillips (1995) . Thermal Responses. Minimum flight temperature of O. georgi was determined to be 19.76 ± 2.50°C ( n = 21). Maximum voluntary tolerance temperature was determined to be 33.13 ± 2.37°C ( n = 19). Heat torpor temperature was determined to be 43.00 ± 1.73°C ( n = 20). The values are related to the habitat and behavior of individual species (see summary in Sanborn 2002 ). Minimum flight temperature has been related to several morphological parameters of the flight system ( Sanborn et al. 2001 ). The mean maximum voluntary tolerance temperature is lower than reported from the cicadas inhabiting Arizona ( Heath and Wilkin 1970 , Heath et al. 1972 , Heath 1972 , Sanborn et al. 1992 ) except the small crepitating Platypedia putnami lutea Davis ( Sanborn et al. 2002 ), which is also a montane species. The value determined for O. georgi is similar to that of cicadas from cooler microclimates or endothermic animals ( Sanborn et al. 1995 a , 2003; Sanborn 2000 , 2004 ). This may be an adaptation to maximize the time of acoustic signaling, because the availability of solar radiation was necessary for the animals to call as stated above. Heat torpor temperature is strictly related to the habitat in cicadas ( Sanborn 2002 ). The heat torpor temperature determined for O. georgi is similar to other cicadas found at altitude such as O. hesperia (Uhler) ( Heath 1972 ) and Cacama ƲalƲata (Uhler) ( Heath et al. 1972 ) or those that inhabit cooler environments or microclimates such as Magicicada cassinii (Fisher) ( Heath 1967 ) , Fidicina torresi Boulrad & Martinelli , Guyalna bonaerensis (Berg) , Quesada gigas (Olivier) , and Proarna insignis Distant ( Sanborn et al. 1995 a , 1995b).