Variation, Distribution and Evolution of the Tabanus (Hybomitra) frontalis Complex of Horse Flies (Diptera: Tabanidae)

Abstract

Nearctic horse flies usually identified as Tabanus (Hybomitra) frontalis Walker or septentrionalis Loew, or simply as T. frontalis septentrionalis complex, have puzzled taxonomists for more than a century. These tabanids (Figs. 1-3), which are among the most widely distributed, most abundant and most troublesome biters of animals and man in North America, are extremely variable, especiallly in color and size. Those who have studied the group have widely different views concerning the taxonomic significance of the variations observed. To date, five nominal species (excluding T. opacus Coq.) have been described from small samples of populations of the group from various parts of Canada, i.e., frontalis and incisus Wlk. (Nova Scotia), septentrionalis Loew and labradorensis Enderlein (Labrador), and canadensis Curran (central Manitoba).