First records of Baetis vernus Curtis (Ephemeroptera: Baetidae) in North America, with morphological notes

• Published in: Journal of the Entomological Society of British Columbia 2018-12, Vol.115, p.3-24
• Main Authors: Burian, Steven K, Erasmus, Daniel J, Shrimpton, Claire M, Currie, Douglas C, Giberson, Donna J, Huber, Dezene P W
• Format: Article
• Language: English
• Subjects: Abdomen; Baetis; Baetis brunneicolor; Cuticles; Cytochrome; Deoxyribonucleic acid; Developmental stages; DNA; Gills; Labrum; Larvae; Library collections; Mandible; Morphology; New records; Segments; Setae; Shading; Spinules; Trachea; Zoology
• ISSN: 0071-0733; 1929-7890

Ståhls and Savolainen (2008) stressed the importance of combining molecular and morphological data to sort out species distributions in this group. [...]recently, only three species in this group were known in North America (McCafferty and Jacobus 2017). Larvae of Baetis vernus can be separated from those of B. brunneicolor by the presence of the following combination of characters: (1) Dorsal surface of body with distinctive contrasting colour pattern of brown with large pale spots and marks (Fig. 27), especially on abdominal terga, terga V and X mostly pale but other terga brown with large paired pale submedian spots, (2) General shape of abdomen from dorsal perspective somewhat cylindrical appearing to very gradually taper from segments I to X, (3) Dorsal surface of labrum with subtriangular raised area flanked by two brown bands that converge medially near base of notch in anterior margin, dorsal setal formula 1+3-4, (4) Prostheca of right mandible with cluster of setae along inner edge near apex, (5) Paraglossae of labium with apices distinctly curved inward, (6) Femora with large blunt setae along outer edge with narrow bases and broad ends, (7) Foretibia and -tarsus slender, (8) Foreclaw with 8-10 denticles that gradually enlarge from base of claw toward tip, (9) Tip of claw not attenuated (i.e., narrowed) beyond denticles, (10) Abdominal terga with distinctive dark brown shading around gill insertions and spinules along posterior margins dark brown, (11) Cuticle of abdominal terga moderately grainy with many distinct cuticular ridges among bases of scale setae, and (12) Abdominal gills 2-4 with only faint traces of the medial trachea and trachea not visible on other gills. Mature larvae of B. brunneicolor can usually be separated from those of B. vernus by the presence of the following combination of characters: (1) Dorsal surface of body relatively uniformly brown, lacking large distinct contrasting pale spots or marks, especially on abdominal terga where some small paired dark marks are present (Fig. 27), Tergite X is usually a uniform light brown on mid-instar larvae but can be pale on black wing pad larvae, (2) General shape of abdomen from dorsal perspective conical appearing to taper more distinctly from segments I to X, (3) Dorsal surface of labrum with rounded raised area with no associated dark bands, dorsal setal formula 1+4-5, (4) Prostheca of right mandible with single row of uniformly spaced setae along inner edge near apex, (5) Paragl