ceramic absorber for the walls and ceiling and SPY-12 pyramidal rubberized absorber for the floor) and separated from the outer box by a vented air space. A styrofoam exposure platform (61 x 61 cm) was situated above the pyramidal absorber and located 121 cm from the horn. Two identical anechoic chambers for sham and microwave exposures, respectively, were situated side by side, 46 cm apart. Because of the low power level utilized in this study, passive cooling of the chambers provided adequate temperature control. The sham and treatment hives (Fig. 2) were 18 x 18 x 22 cm boxes constructed of nonmetallic materials. The sides and removable top were made of pine (2 cm thick); the front and back were made of box shook (0.64 cm thick). Hives were assembled with glue (Weldwood Resorcinol water proof). Each hive was ventilated through a front entrance-exit hole and a back ventilation hole (both 3 cm diam), the latter covered with fiberglass screen. During the exposure period, each colony contained 4 beeswax combs (10 x 3 x 14 cm) in wooden frames that were parallel to the front wall of the hive. A runway system (Fig. 1) connected each hive to a separate exit hole leading to the outside and permitted bees to enter and exit freely, thereby providing the opportunity for normal foraging activities. Extending from the hive entrance to the chamber wall was a styrofoam runway (21 x 15 x 5 cm) (Fig. 1, H) covered with fiberglass screen. This runway and the hive rested on a piece of 0.64 cm thick plywood (41 x 20 cm) on top of the styrofoam exposure platform. Two Plexiglas® tubes (15 cm long, 0.95 cm i.d. and 1.3 cm o.d.) extended from the styrofoam runway
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