WILLIAMS, J.B.*; RUEHL, N.C.; LEE, R.E.; Miami University; Miami University; Miami University: Partial links between the seasonal acquisition of cold tolerance and desiccation resistance in the goldenrod gall fly Eurosta solidaginis

Larvae of the goldenrod gall fly, Eurosta solidaginis (Diptera: Tephritidae), enhance their cold hardiness and desiccation resistance as they prepare for winter. In mid-September, gall tissues are well hydrated but later may become extremely dry as the plant senesces. Freeze tolerance gradually increased during the autumn and on Oct. 30 all larvae survived at least -20�C for 24 h. During this period there was a concomitant increase in hemolymph osmolality, consistent with previous reports of cryoprotectant (glycerol and sorbitol) accumulation. In contrast to the steady increase in cold tolerance, resistance to desiccation increased abruptly between Oct. 3 and Oct. 16. The dramatic increase in desiccation resistance was associated with drying of the gall tissue: water loss rates decreased by 83.6% as water vapor potential of the gall tissues became equal with that of the larvae. In a separate experiment, desiccated larvae significantly increased their resistance to water loss compared to larvae held at more humid conditions. Later in the season, water loss rates continued to decrease in correlation with increasing hemolymph osmolality, and thus suggests a link to cold hardening. Supported by NSF#IBN-0090204