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Title: Horn fly, Haematobia irritans irritans L., overwintering

item Showler, Allan
item Osbrink, Weste
item Lohmeyer, Kimberly - Kim

Submitted to: International Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/3/2014
Publication Date: 5/21/2014
Citation: Showler, A., Osbrink, W.L., Lohmeyer, K.H. 2014. Horn fly, Haematobia irritans irritans L., overwintering. International Journal of Insect Science. 6:43-47.

Interpretive Summary: Overwinter diapause in the horn fly has largely been assumed as the pest's mode for surviving, but studies indicate that horn fly diapause does not always occur. Although adult numbers on cattle usually fluctuate seasonally, definitive criteria for horn fly diapause have not been identified, and analyses of diapause are inconclusive. Diapause induction and termination cues are shown to be contradictory. Other modes of overwintering are more likely and overwinter survival in cold conditions is poor.

Technical Abstract: Putative diapause in the horn fly, Haematobia irritans irritans (L.), has frequently been assumed as the pest's mode for overwinter survival from the tropics to temperate regions of northern and southern hemispheres. Examination of the scientific literature indicates that putative horn fly diapause is "facultative" because it does not always occur. While it is certain that adult populations on cattle generally fluctuate on a seasonal basis, with low numbers occurring in regions with cold winters, studies do not indicate the criteria by which the term "diapause" has been assigned. Horn fly behavioral, biochemical, and genetic analyses relating to the possibility of diapause are inconclusive. Similarly, assessment of diapause induction and termination cues has revealed contradictions and conditions attributable to other, nondiapause, forms of overwintering, and suggests that diapause, even if it does occur in the horn fly, might not be a substantially effective mechanism for surviving environmental extremes.