Submitted to: Entomologia Experimentalis et Applicata
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 20, 2010
Publication Date: N/A
Interpretive Summary: Hessian fly is an invasive insect in North America, introduced during the Revolutionary War. Since its introduction, it has posed great economic harm to wheat production on the North American Continent. In temperate regions, the Hessian fly has to survive through cold dry winter months and hot, dry summer months. Within the course of one year, a Hessian fly pupa may enter a summer diapause, a winter diapause, or both, depending on the latitude of their habitat. Winter and summer, because they are dry, are metabolically taxing for maintaining water balance for species like Hessian fly. The Hessian fly’s inability to migrate means it must rely on water acquired before it pupates and enters the dry seasons. In this study, we looked at the water balance requirements of winter diapause, summer diapause and non-diapausing Hessian flies. We wanted to see if there were similar water profiles between these flies. Based on our results, diapausing pupae are more resistant to dehydration than non-diapausing pupae.
Technical Abstract: We report the water balance of aestivating (summer), diapausing (winter), and non-diapausing pupae of Hessian fly, Mayetiola destructor (Say) (Diptera: Cecidomyiidae). Maintaining water requirements during pupal dormancy is particularly important because water cannot be replenished actively by drinking. Dehydration tolerance (25%loss before succumbing to dehydration) and water content (63–65%) were not different for the three types of pupae. Differences were noted in the net transpiration rates (NTRs, % body water per hour at 0% r.h.) between dormant (0.24–0.28% per hour) and non-diapausing (0.47%per hour) pupae 10 days after pupariation, but not between aestivating (0.28% per hour) and diapausing (0.24% per hour) pupae. These reduced NTRs result in extended pupal survival, indicated by adult eclosion, during exposure to dehydrating conditions. Net transpiration rates for aestivating and diapausing pupae were further reduced as dormancy progressed (up to 130 days) until individuals were moved to conditions that break dormancy. Pupae could not take up water from the atmosphere below vapor saturation (100%r.h. or 1.00 av), and rely upon contact with liquid water or moist plant tissue to replenish their water stores. The critical transition temperatures (CTT) of the aestivating and diapausing pupae were significantly higher than those of non-diapausing pupae, suggesting that modified cuticular lipids are present on aestivating and diapausing pupae. Thus, aestivation and diapause trigger a dormancy specific water balance profile characterized by reduced NTRs and increased CTTs.