Submitted to: Journal of Insect Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 18, 1995
Publication Date: N/A
Interpretive Summary: Horn flies are frequently used in various field trials and laboratory bioassays, and for convenience or from necessity, pupae may be stored at low temperatures for various periods prior to use. In addition to artificial low temperature storage, horn flies may experience similar conditions in nature during the fall and spring when temperatures are erratic. Little is know of the short- or long-term effects of such cold exposure on physiological processes and life history traits of these flies. The purpose of this study was to evaluate both the short- and long-term consequences of cold stress (at 4oC) on horn fly pupae and later life stages. The effects of low temperature exposure were substantial. Longer storage (up to 4 weeks) had greater deleterious effects on several life history traits. Exposures for 2-4 weeks reduced adult emergence, survivorship, mating performance, ovarian and follicular development, total egg production, f1 egg hatch, and f1 larval development. Cold stress, therefore, results in reduced overall population performance. Pupal storage at 4oC for 2 weeks or longer renders these flies unsuitable for bioassays or laboratory colony maintenance.
Technical Abstract: The effects of low temperature (4oC) exposure on Haematobia irritans pupae were substantial, and were both immediate, in terms of survival/failure, and long-term, in terms of effects on several life history traits. Deleterious effects of cold exposure were positively correlated with duration of exposure. Exposure of pupae to 4oC for 2-4 weeks significantly reduced eclosion, survivorship, mating performance, ovarian and follicular development, total fecundity, f1 egg hatch, and f1 larval development. Exposures of 1 week increased performance in several of these categories when compared to a control group. The results of this study demonstrated that success/failure evaluations of cold tolerance are inadequate for assessing ecologically relevant consequences of cold exposure. Late fall or early spring conditions may result in exposures of non-diapausing H. irritans pupae to periods of cold stress, resulting in reduced population fitness. Pupal storage at 4oC for 2 weeks or longer renders these flies unsuitable for bioassays or laboratory colony maintenance.