THE EFFECTS OF TEMPERATURE AND SEASON ON THE O-2 CONSUMPTION OF 3RD-INSTAR LARVAE OF THE GOLDENROD GALL FLY (EUROSTA-SOLIDAGINIS)

Third-instar larvae of the goldenrod gall fly (Eurosta solidaginis Fit ch) live inside ball galls on goldenrod plants from summer to the foll owing spring, Because galls are highly exposed to the weather, larvae experience substantial variations in body temperature. This study docu ments the oxygen consumption of gall fly larvae with regard to the eff ects of ambient temperature, seasonal conditioning, and prior exposure to subzero temperature. The body mass of larvae doubles between the l ate summer and the autumn; it subsequently undergoes a modest decline by early winter. The O-2 consumption of field-acclimatized larvae incr eases with ambient temperature, especially between 0 and 10 degrees C (Q(10) = 2.6-3.4). The thermal sensitivity of metabolism declines at h igher ambient temperatures, most notably during the autumn/early winte r. After exposure to 15 degrees C for 1 week, autumn and early winter larvae maintain much lower rates of O-2 consumption than do late summe r specimens. Prior exposure to -5 degrees C for 24 h did not influence the O-2 consumption of larvae. Low thermal sensitivity of O-2 consump tion, especially at higher ambient temperatures, is an energy-sparing mechanism during seasonal inactivity. Indeed, the persistence of this metabolic pattern in larvae exposed to 15 degrees C suggests that they have entered a state of diapause.