The polytene chromosomes of North American blackflies in the Eusimulium canonicolum group (Diptera: Simuliidae)

The polytene chromosomes of four taxa are described. These are (i) Eusimulium canonicolum Dyar and Shannon from four sites in Alberta; (ii) Eusimulium emarginatum (Davies, Peterson &Wood) from sites in Ontario, West Virginia, and Pennsylvania; (iii) Eusimulium euryadminiculum (Davies) with samples from Newfoundland, Ontario, Saskatchewan, and Alberta; and (iv) "Hinton," an undescribed species from western Alberta. These four taxa form a cytologically cohesive group, and they are characterized in terms of fixed inversion differences, sex differential segments, and inversion polymorphisms. Polytene chromosome idiograms and a cytophylogeny are presented. The morphologically related Eusimulium johannseni (Hart) is excluded on the grounds of its stronger chromosomal affiliation with the Eusimulium vernum group.