Keys to Aquatic Heteroptera of Western Canada
I have attempted to assemble as a reference some keys to Notonectidae and Corixidae of Western Canada. Although I believe these keys to be accurate, they have not been thoroughly tested, and I do not consider myself an expert in this group. Nevertheless, I hope they may be useful, at least as a starting point.
Notonectidae
| 1a. | Relatively small; where the hemelytra meet, at the anterior end there is a hair-lined pit (commissure) | 2 |
| 2a. | Pronotum distinctly broader than head at its widest point; [known from nearby WA, ID] | Buenoa margaritacea |
| 2b. | Pronotum no wider than head | 3 |
| 3a. | Narrowest dorsal distance between eyes (synthlipsis) much narrower than anterior vertex width; [AB, BC, SK] | B. confusa |
| 3b. | Synthlipsis at least half the anterior vertex width; [BC, SK] | B. macrotibialis |
| 1b. | Relatively large; no commissure where the hemelytra meet | 4 |
| 4a. | Keel of fourth abdominal sternite bare, with hairs restricted to sides | 5 |
| 5a. | Hemelytra mostly made of substantial dark/black and orange patches; [BC, AB, SK, YK, NT] | Notonecta kirbyi |
| 5b. | Hemelytra mostly white; generally stubbier than other pale Notonecta species in Western Canada; [BC, AB, SK, NT] | N. borealis |
| 4b. | Keel of fourth sternite not bare | 6 |
| 6a. | Hemelytra darkly coloured, and generally with orange reticulation; [SK] | N. irrorata |
| 6b. | Hemelytra usually predominantly pale | 7 |
| 7a. | Mesotrochanter nearly rounded; hemelytra typically white with one transverse black band; [BC, AB, SK, NT] | N. undulata |
| 7b. | Mesotrochanter angular or tooth-like | 8 |
| 8a. | Mesotrochanter extended into a spine; synthlipsis less than half anterior vertex width; [BC, AB] | N. spinosa |
| 8b. | Mesotrochanter not spine-like; synthlipsis at least half anterior vertex width; [BC] | N. unifasciata |
From Hungerford, 1933; Menke, 1979.
Corixidae Genera
Identification of Corixidae is generally difficult or impossible without physical male specimens for close examination. Males are recognized because the segments of their abdomen are asymmetrical. Certain features, especially the shape of the dorsal surface of the abdomen beneath the wing covers (including the strigil) as well as the pala (fore tarsus) are highly important for identification.
| 1a. | Body shape distinctive, unlike any other species in area; male without strigil (Cymatinae) | Cymatia americana |
| 1b. | Body shape typical; strigil present or absent (Corixinae) | 2 |
| 2a. | Eyes bulging (Glaenocorisini) | 3 |
| 3a. | Male pala significantly dorsally expanded at base; northern, mostly known from the territories | Glaenocorisa |
| 3b. | Male pala not dorsally expanded at base | Dasycorixa |
| 2b. | Eyes normal (Corixini) | 4 |
| 4a. | Male lacking strigil, or male with strigil on left | 5 |
| 5a. | Male lacking strigil | Callicorixa |
| 5b. | Male with strigil on left | Trichocorixa |
| 4b. | Male with strigil on right | 6 |
| 6a. | Rear margin of head sharply curved; interocular space much shorter than the width of an eye | Palmacorixa |
| 6b. | Not as above | 7 |
| 7a. | Generally large species; prothoracic lobe about as long as wide | Hesperocorixa |
| 7b. | Prothoracic lobe distinctly elongate | 8 |
| 8a. | Pronotum and clavus mostly smooth and shiny | Corisella |
| 8b. | Pronotum and clavus distinctly rough, either rastrate, rugose, or both | 9 |
| 9a. | Clavus predominantly with broad, distinct transverse bands; pronotal carina absent or at most faintly expressed at anterior margin | Sigara |
| 9b. | Clavus reticulate, or rarely with irregular transverse bands broken and merging; at least anterior 1/3 of pronotum with medial carina | 10 |
| 10a. | Median pronotal carina well-defined; male pala elongate | Arctocorisa |
| 10b. | Median pronotal carina usually only visible on anterior third; male pala broad | Cenocorixa |
References
Checklist of Hemiptera of Canada and Alaska. Maw et al., 2000.
A revision of the genus Buenoa (Notonectidae, Hemiptera). Truxal, 1952.
The genus Notonecta of the world (Notonectidae-Hemiptera). Hungerford, 1933.
Aquatic Heteroptera (Notonectidae and Macroveliidae) new to Washington and Idaho. Jack, 1990.
The semiaquatic and aquatic Hemiptera of California. Menke, 1979.
The Corixidae of Oregon and Washington (Hemiptera: Heteroptera). Stonedahl & Lattin, 1986.
The Corixidae of the Western Hemisphere (Hemiptera). Hungerford, 1948.
New Provincial and State Records for Heteroptera (Hemiptera) in Canada and the United States. Scudder, 2008.
New Waterboatman Records for Western Canada (Hemiptera: Corixidae). Kenner & Needham, 2004.
New Waterboatman Records from Alberta, Canada (Hemiptera: Corixidae). Lapierre et al., 2020.
Nine Heteroptera (Hemiptera) new to Canada, with Additional New Provincial Records for Three Other Species in Canada. Scudder, 2009.
