WILLIAMS, J.B.*; RUEHL, N. C. ; LEE, R. E.; Miami University, Oxford, Ohio; Miami University, Oxford, Ohio; Miami University, Oxford, Ohio: Links between cold hardiness and desiccation resistance in an overwintering insect

To investigate possible links between cold-hardiness and desiccation resistance in insects, we examined changes in seasonal parameters associated with these phenomena in overwintering larvae of the goldenrod gall fly Eurosta solidaginis. During the autumn, field-collected larvae gradually increased their capacity to survive freezing concomitantly with increases in cryoprotectants as measured by hemolymph osmolality (488 to 870 mOsm�Kg^-1). In contrast to gradual increases in larval cold hardiness, resistance to desiccation increased in two distinct phases. An initial 6-fold decrease in rates of water loss occurred in a two-week period in early October, reaching 0.57 �g�mm^-2�h^-1; this phase was primarily due to a reduction in respiratory water loss as the larvae entered diapause. The second phase was a more subtle 4-fold reduction that occurred over eight weeks beginning in mid-October. Interestingly, the second phase of reduced rates of water loss correlated strongly with increased hemolymph osmolality (568 to 870 mOsm�Kg^-1). In addition, we acclimated larvae at various temperatures in order to manipulate cryoprotectant concentrations. Our preliminary results suggest a trend exists between higher hemolymph osmolalities and lower rates of water loss. Taken together these data suggest that cryoprotectants may promote desiccation resistance as well as cold-hardiness in overwintering insects. Supported by NSF#IBN-0090204.