Microhabitat segregation and physiological differences in co-occurring tiger beetle species, Cicindela oregona and Cicindela tranquebarica.

The daily movements of two co-occurring tiger beetle species were monitored in conjunction with changes in microclimate along streams in Northeast Arizona. Cicindela oregona and C. tranquebarica temporarily segregated across areas of beach exhibiting different microclimates. C. oregona progressively moved from the dry upper beach to the wet stream edge as beach temperatures increased and humidity decreased. The actively foraged throughout the day in this moist habitat at air temperatures between 25 and 38°C. C. tranquebarica remained on the dry, upper portions of the beach and shuttled between sun and shade at air temperatures above 35°C. Only when stream edge temperatures exceeded 30°C was tranquebarica found in this subhabitat. Both species exhibited physiological tolerances in the laboratory that were consistent with their microhabitat preferences in the field. Although both species had similar high lethal temperatures (47-48°C) in saturated air, oregona died at lower temperatures (39-43°C) than tranquebarica (46-47°C) under dry (0% RH) conditions. C. oregona was considerably more active than tranquebarica at body temperatures below 30°C and exhibited higher levels of active metabolism between 25 and 40°C. In addition, C. tranquebarica exhibited significantly lower water loss rates than oregona at 30, 35 and 40°C.

Effect of antecedent muscle tension levels on motor behavior.

In Experiment 1 there was an appreciable elevation in the levels of electromyographic activity recorded from the right forearm flexor of intercollegiate wrestlers prior to an important competition. With the aid of biofeedback, subjects in the second experiment maintained these same elevated levels of electromyographic activity before performing a battery of simple motor tasks. These elevated levels of antecedent muscle tension were found to disrupt hand steadiness and grip strength. Thus, the high levels of pre-competition muscle tension occurring in athletes are capable of disrupting performance. The use of biofeedback relaxation techniques in the pre-competition period may significantly improve the performance of competitive athletes hampered by particularly high levels of pre-competition muscle tension.