Aquatic
Insects of Michigan
by
Ethan Bright, Museum of Zoology Insect Division and School of Natural
Resources and Environment
University of Michigan
Baetidae of Michigan
Key to Adult Baetidae of Michigan
(adapted from Waltz and Burian 2007)
| 1a | a. Hind wings present and with a blunt costal projection and 10 or more crossveins | Callibaetis Eaton |
| b. Abdomen with distinct dark speckles | ||
| c. Forewings of most species patterned | ||
| 1b | a. Hind wings present or absent, if present, then usually with less than 6 crossveins | 2 |
| b. Abdomen variable, rarely with speckles | ||
| c. Forewings of most species without patterns | ||
| also: Costal projection of hind wings never blunt, either pointed, hooked, or absent | ||
| 2a(1b) | a. Marginal intercalaries of forewings occur singly | 3 |
| b. Hind wings present or absent, if present, hind wings with costal projection hooked or recurved | ||
| 2b | a. Marginal intercalaries of forewings occur in pairs | 6 |
| b. Hind wings present or absent, if present, costal projection of hind wings variable, rarely hooked | ||
| 3a(2b) | a. Males with spine-like process present between the forceps of most species | Centroptilum Eaton |
| b. Terminal segment of forceps elongate | ||
| 3b | a. Males without a spine-like process between forceps | 4 |
| b. Terminal segment of forceps variable | ||
| 4a(3b) | a. Hind wings absent and male genitalia with distinct coniform penes cover between the forceps bases | Cloeon Leach |
| b. Terminal segment of forceps small, rounded | ||
| c. Females with brownish pigment at the pterostigma of forewings | ||
| 4b | a. Hind wings present or absent, and male genitalia with rounded or rectangular penes cover between forceps bases | 5 |
| b. Terminal segment of the forceps usually elongate | ||
| c. Females without brownish pigment at the pterostigma of forewings | ||
| 5a(4b) | Segment 2 of male forceps with a distinct inner swelling or bulge |
Pseudocentroptiloides usa Waltz and McCafferty |
| 5b | Segment 2 of male forceps without distinct swelling or bulge | Procloeon Bengtsson |
| 6a(2b) | a. Anterior process of mesothorax coniform, projecting dorsally |
7 |
| b. Hind wings present or absent, if present, hind wings without a costal process | ||
| 6b | a. Anterior process of mesothorax not coniform and not projecting dorsally | 8 |
| b. Hind wings, when present, with or without a costal process | ||
| 7a(6a) | Hind wings minute, without veins |
Heterocloeon curiosum (McDunnough) |
| 7b | Hind wings present or absent, when present, with 2 longitudinal veins | Acentrella Bengtsson |
| 8a(6b) | a. Hind wings without a costal process, or with costal process greatly reduced |
Pseudocloeon Klapálek |
| also: Distinct plate present between forceps bases of male; terminal segment of forceps small and rounded | ||
| 8b | a. Hind wings present or absent, if present, hind wings with a costal process | 9 |
| 9a(8b) | Hind wings with a second longitudinal vein forked, vertex or fork proximad and toward wing base | Diphetor hageni (Eaton) |
| also: Terminal segment of male forceps elongate | ||
| 9b | Hind wings present or absent, if present, hind wings with second vein simple, or if forked, vertex or fork occurs distally beyond the middle of the hind wing | 10 |
| 10a(9b) | Costal process of hind wing acute, prominent, with a curbed anterior margin preceding the costal process |
Acerpenna Waltz and McCafferty |
| also: Beyond the costal process, anterior margin of hind wing undulate; terminal segment of male forceps approximately 4x long as wide | ||
| 10b | Hind wings present or absent, if present, hind wing costal process variable, not as acute or prominent as above | 11 |
| also: Terminal segment of male forceps variable | ||
| 11a(10b) | Hind wings present |
Baetis Leach (in part) |
| 11b | Hind wings absent or, if present, small, slender, with only 2 longitudinal veins | 12 |
| 12a(11b) | a. Small species, maximal forewing length 2.5-4.5 mm | Paracloeodes minutus (Daggy) |
| b. Terminal segment of male forceps elongate, cylindrical, with terminal segment of forceps about 2.5-3.0x longer than wide | ||
| c. Male genitalia without small rectangular plate between forceps bases | ||
| 12b | a. Larger species, forewing length generally > 4.0 mm | 13 |
| b. Terminal segment of male genitalia not elongate, only about as long as wide | ||
| c. Male genitalia with a small rectangular plate between forceps bases | ||
| 13a(12b) | a. Forceps of male strongly curved |
Plauditus Lugo-Ortiz and McCafferty |
| b. Ab3-4 terga strongly pigmented in red medially, with Ab5-6 terga washed in red | ||
| c. Rectangular plate present between male forceps bases | ||
| 13b | a. Forceps of male not strongly curved as above | Baetis Leach (in part) |
| b. Abdominal terga not pigmented as above | ||
| c. Rectangular plate usually absent between male forceps bases | ||
Key to the mature nymphs of Baetidae in Michigan (adopted from Waltz and Burian 2007)
| 1a | a. Apex of the labial palpi simple and truncate |
2 |
| b. Trachae of gills palmate, or asymmetrical with most branches on median side | ||
| c. Tails with a distinct dark band every third to fifth segment | ||
| d. Gills simple, or with dorsal flaps on one or more abdominal segments | ||
| 1b | a. Apex of the labial palpi variable, but not truncate as above | 4 |
| b. Trachae variable | ||
| c. Tails rarely banded as above | ||
| d. Gills simple, or large and compound | ||
| 2a(1a) | a. Labrum with a deep triangular median notch at the distal margin |
Pseudocentroptiloides usa Waltz and McCafferty |
| b. Paraglossae broad, longer than the glossae | ||
| c. Claws longer than their respective tarsi | ||
| d. Gills simple | ||
| 2b | a. Labrum with a small median notch along the median margin | 3 |
| b. Paraglossae subequal to the glossae | ||
| c. Claws usually shorter than their respective tarsi | ||
| d. Gills simple, or with dorsal flaps | ||
| 3a(2b) | a. Mandible incisors deeply cleft to the base, or united less than 0.5x the height of the incisors |
Centroptilum Eaton |
| b. Length of segment 3 of the maxillary palp subequal to segment 2 | ||
| c. Laterla bristles of the caudal filaments present on proximal three-fourths, apices of the filaments without bristles | ||
| d. Gills simple | ||
| 3b | a. Mandible incisors united above the base, or fused to the apex | Procloeon Bengtsson |
| b. Length of segment 3 of the maxillary palp, when present, shorter than segment 2 | ||
| c. Laterla bristles of the caudal filaments present to filament apices | ||
| d. Gills simple, or with a dorsal flap at least on Ab1 | ||
| 4a(1b) | Gills on one or more segments compound, with distinct large flaps |
5 |
| 4b | Gills simple | 6 |
| 5a(4a) | a. Labial palpi apparently 2-segmented, blunt apically |
Callibaetis Eaton |
| b. Hind wing pads present | ||
| c. Gills with recurved flaps folded ventrally | ||
| 5b | a. Labial palpi 3-segmented, obliquely truncate apically | Cloeon dipterum (Linnaeus) |
| b. Hind wing pads absent | ||
| c. Gills with recurved flaps folded dorsally | ||
| 6a(4b) | Claws about one-half as long as the resepctive tarsi |
Paracloeodes minutus (Daggy) |
| 6b | Claws clearly less than one-half as long as the respective tarsi | 7 |
| 7a(6b) | a. Villopore present on all or some legs | 8 |
| b. Terminal filament subequal or reduced to the cerci | ||
| c. Mandibles without setae between the prostheca and molars | ||
| 7b | a. Villopore absent on all legs | 14 |
| b. Terminal filament subequal to the cerci | ||
| c. Mandibles with setae on the surface between the prostheca and the molars or, if mandibles lack setae in this area, the prostheca of the right mandible is reduced to a single simple setae | ||
| 8a(7a) | a. Antennal scape with a distal lobe | Pseudocloeon Klapálek |
| b. Maxillary palps with a subapical excavation | ||
| c. Segment 2 of labial palps greatly expanded medially | ||
| d. Villopore often reduced or absent on the forefemora | ||
| 8b | a. Antennal scape without a distal lobe | 9 |
| b. Maxillary palps without a subapical excavation | ||
| c. Segment 2 of labial palps variable, but not greatly expanded as above | ||
| d. Villopore usually well-developed on forefemora | ||
| 9a(8b) | a. Terminal filament well-developed |
Baetis Leach (in part) |
| b. Hind wing pads present | ||
| 9b | a. Terminal filament reduced | 10 |
| b. Hind wing pads absent or present | ||
| 10a(9b) | a. Tarsal claws with two rows of denticles, or a row of denticles and a secondary ridge that may be serrate or not (these claw characters require viewing at 400x) |
Heterocloeon curiosum (McDunnough) |
| b. Terminal filament minute to a visible stub not longer than Ab10 tergite | ||
| c. Procoxae with or without gills | ||
| 10b | a. Tarsal claws with a single row of denticles | 11 |
| b. Terminal filament reduced, but longer than Ab10 tergite | ||
| c. Procoxae without gills | ||
| 11a(10b) | Hind wing pads present (although sometimes reduced to a small thread-like flap) |
12 |
| 11b | Hind wing pads absent | 13 |
| 12a(11a) | a. Segment 2 of labial palp with a well-developed medially-projecting corner |
Baetis Leach (in part) |
| b. Abdominal tergal scale-like setae present | ||
| 12b | a. Segment 2 of labial palps without a well-developed medially-projecting corner | Acentrella Bengtsson (in part) |
| b. Abdominal tergal scale-like setae absent | ||
| 13a(11b) | a. Femora, tibiae, and tarsi without a row of long setae on the outer margin |
Plauditus Lugo-Ortiz and McCafferty |
| b. Labial palps as in picture, with the inner apical edge of segment 3 more or less straight (i.e., not forming a smooth curve to the apex) | ||
| 13b | a. Femora, tibiae, and tarsi with a row of long setae on the outer margins, or the femora and tibiae with a few long setae but none on the tarsi | Acentrella Bengtsson (in part) |
| b. Labial palps as in picture, with the inner apical edge of segment 3 smoothly curved | ||
| 14a(7b) | Gills present on Ab2-7 |
Diphetor hageni (Eaton) |
| also: Segment 2 of labial palps without a well-developed medial digitate-lobe; paraglossae not rectangular, but more broadly rounded apically; prostheca of right mandible slender, bifid, and minutely pectinate | ||
| 14b | Gills present on Ab1-7, gill 7 slender to apically pointed | Acerpenna Waltz and McCafferty |
| also: Segment 2 of labial palp with a well-developed anteriorly projecting digitate-lobe; Claws with one row of denticles, and without unparied subapical setae; no tuffs of setae on abdominal sterna | ||
References
Waltz RD, Burian SK. 2007. Ephemeroptera, pp. 181-236 in Merritt RW, Cummins KW, Berg MB (eds.), An Introduction to the Aquatic Insects of North America, Fourth Edition. Kendall/Hunt Publishing Company, Dubuque, Iowa, USA.
Last updated: October 19, 2007 (EB)