Aquatic Insects of Michigan
by Ethan Bright, Museum of Zoology Insect Division and School of Natural Resources and Environment
University of Michigan
- Home
- Species Lists
- Coleoptera
- Diptera
- Ephemeroptera
- Acanthametropodidae
- Ameletidae
- Ametropodidae
- Arthropleidae
- Baetidae
- Baetiscidae
- Behningiidae
- Caenidae
- Ephemerellidae
- Ephemeridae
- Heptageniidae
- Isonychiidae
- Leptohyphidae
- Leptophlebiidae
- Metretopodidae
- Neoephemeridae
- Oligoneuriidae
- Palingeniidae
- Polymitarcyidae
- Potamanthidae
- Pseudironidae
- Siphlonuridae
- Heteroptera
- Hymenoptera
- Lepidoptera
- Megaloptera
- Neuroptera (Sisyridae)
- Odonata
- Orthoptera
- Plecoptera
- Trichoptera
- Other Orders
- Keys/Identification
- Aquatic Insects of Michigan
Stenonema (Ephemeroptera: Heptageniidae)
Adults (adapted from Bednarik and McCafferty 1979)
| 1a | Males | 2 |
| 1b | Females | 20 |
| 2a(1b) | a. Posterior margins of Ab3-8 terga each with a median dot and a pair of transverse submedian dashes | Stenonema femoratum (Say) |
| b. Fore wings with crossveins crowded in at least 3 interspaces of the bulla region | ||
| 2b | a. Posterior margins of Ab3-8 terga each without above markings | 3 |
| b. Fore wings with crossveins crowded or not crowded in the first 3 interspaces of the bulla region | ||
| 3a(2b) | Compound eyes separated dorsally by the distance equal to, or less than, the maximum width of the lateral ocellus | 4 |
| also: Fore wings with crossveins either crowded in the first 3 interspaces of the bulla region, or not crowded at all; hind wings with outer margins not darkened | ||
| 3b | Compound eyes separated dorsally by the distance greater than the maximum width of the lateral ocellus | 6 |
| 4a(3a) | Fore tarsal ratio 3.5 or more | Stenonema vicarium (Walker) (in part) |
| 4b | Fore tarsal ratio less than 3.5 also: Penes more or less boot-shaped | 5 |
| 5a(4b) | a. Mesonota and abdominal terga with a reddish-brown cast | Stenonema ithaca (Clemens and Leonard) |
| b. Posterior margins of abdominal sterna narrowly to broadly darkened, resulting in more or less annulate appearance | ||
| 5b | a. Mesonota and abdominal terga brown | Stenonema vicarium (Walker) (in part) |
| b. Abdominal sterna immaculate or with variable brown patches and shading, but posterior margins not as above | ||
| 6a(3b) | Spiracular marks absent | 7 |
| 6a | Spiracular marks present | 10 |
| 7a(6a) | Hind wings with outer margins darkened | 8 |
| 7b | Hind wings with outer margins not darkened | 9 |
| 8a(7a) | a. Penes shaped as in figure | Stenonema exiguum Traver (in part) |
| b. Fore tarsal ratio 1.3-1.9 | ||
| c. Distinct reddish tinge in the stigmatic area | ||
| d. Median band on the middle and hind femora | ||
| 8b | a. Penes less rounded, shaped as in figure | Stenonema terminatum (Walsh) (in part) |
| b. Fore tarsal ratio < 1.5 | ||
| c. Faint reddish tinge in stigmatic area | ||
| d. Median band absent, or faint on the middle and hind femora | ||
| 9a(7b) | Crossbands present at the posterior margins of Ab2-7 terga, sometimes enclosing narrow dashes | Stenonema terminatum (Walsh) (in part) |
| 9b | Narrow crosslines present at the posterior margins of Ab2-7 terga | Stenonema luteum (Clemens) |
| 9c | Submedian transverse dashes present at the posterior margins of Ab2-7 | Stenonema terminatum (Walsh) (in part) |
| 10a(6a) | Ab2-7 terga with short median transverse lines at the posterior margins | 11 |
| 10b | Ab2-7 terga with posterior transverse lines extending across segments | 12 |
| 11(10a) | a. Thorax deep black-brown |
Stenonema mediopunctatum (McDunnough)(in part) |
| b. Caudal filaments entirely white | ||
| 11b | a. Thorax pale brownish or clay colored | Stenonema modestum (Banks)(in part) |
| b. Part of caudal filaments with alternate segment articulations pigmented | ||
| 12a(10b) | Hind wings with darkened outer margins | Stenonema exiguum Traver (in part) |
| 12b | Hind wings without darkened outer margins | 13 |
| 13a(12b) | Fore wings with 2 or 3 crossveins in each of the first 3 bulla interspaces | Stenonema modestum (Banks)(in part) |
| 13b | Fore wings with 1 or 2 crossveins in each of the first 3 bulla interspaces (if 3 present in the the third interspace, then 1 crossvein in the first interspace) | 14 |
| 14a(13b) | a. Thoracic nota deep brown to black | 15 |
| b. Penes as in figure | ||
| c. Body length < 7 mm | ||
| 14b | a. Thoracic nota pale yellowish brown | 17 |
| b. Penes shaped as in figure | ||
| c. Body length > 8 mm | ||
| 15a(14a) | a. Mesoscutellum brown | Stenonema modestum (Banks)(in part) |
| b. Fore tarsal ratio 1.1-1.3 | ||
| 15b | a. Mesoscutellum white or white-tipped | 16 |
| b. Fore tarsal ratio > 1.4 (usually 1.7) | ||
| 16a(15b) | a. Mesoscutellum entirely white | Stenonema pulchellum (Walsh) |
| b. Fore wings with 1 or 2 crossveins in each of the interspaces 2 and 3 of bulla regions | ||
| c. Abdominal terga generally white | ||
| 16b | a. Mesoscutellum white-tipped | Stenonema modestum (Banks)(in part) |
| b. Fore wings with 2 or 3 crossveins in at least 2 of the first 3 interspaces of the bulla regions | ||
| c. Abdominal terga slightly infumated | ||
| 17a(14b) | Fore wings with the stigmatic area opaque-white, without reddish stain | Stenonema modestum (Banks)(in part) |
| 17b | Fore wings with a distinct reddish stain in the stigmatic area | 18 |
| 18a(17b) | a. Mesoscutellum with a median pale area tinged with pigmentation | Stenonema modestum (Banks)(in part) |
| b. Compound eyes usually as in figure | ||
| c. Penes shaped as in figure | ||
| 18b | a. Mesoscutellum white, never tinged with pigmentation | 19 |
| b. Compound eyes as in figure | ||
| c. Penes shaped as in figure | ||
| 19a(18b) | a. Ab8 tergum nearly entirely shaded with pinkish brown | Stenonema mediopunctatum (McDunnough)(in part) |
| b. Mesonotum ocher-brown | ||
| c. Fore tarsal ratio < 2.0 | ||
| 19b | a. Ab8 tergum with median longitudinal pinkish brown shading only | Stenonema modestum (Banks)(in part) |
| b. Mesonotum light clay colored | ||
| c. Fore tarsal ratio usually > 2.0 | ||
| note: few species of female Stenonema can be conclusively differentiated without association with nymphs or male imagoes | ||
| 20a(1b) | Ab2-8 terga with a median black dot and a pair of transverse submedian dashes | Stenonema femoratum (Say) |
| 21b | Ab2-8 terga without the above markings | 22 |
| 22a(21b) | Ab2-7 terga each with a broad brown transverse band on the posterior 1/4 or more of the segment, and/or a dark middorsal band | Stenonema vicarium (Walker),Stenonema ithaca (Clemens and Leonard) |
| 22b | Ab2-7 terga variable, but without the markings as above | 23 |
| 23a(22b) | Longitudinal middorsal lines on Ab3 and Ab6 terga | Stenonema mexicanum integrum (McDunnough) |
| 23b | No longitudinal middorsal lines on Ab3 and Ab6 terga | 24 |
| 24a(23b) | Spiracular marks absent | 25 |
| 24b | Spiracular marks present | 26 |
| 25a(24b) | Ab2-7 with a transverse band only, the band enclosing a pair of short, submedian dashes, or with a pair of short, submedian dashes only on the posterior margin |
Stenonema terminatum (Walsh)(in part) |
| 25b | Ab2-7 with narrow, transverse lines on the posterior margin | Stenonema terminatum (Walsh)(in part), Stenonema exiguum Traver (in part), Stenonema luteum (Clemens) |
| 26a(25b) | Ab2-7 terga with short median transverse dashes on the posterior margin | Stenonema mediopunctatum (McDunnough) (in part), Stenonema modestum (Banks)(in part) |
| 26b | Ab2-7 terga with narrow transverse line on the posterior margin | Stenonema mediopunctatum (McDunnough) (in part), Stenonema modestum (Banks)(in part), Stenonema pulchelium (Walsh) |
Mature nymphs (adapted from Bednarik and McCafferty 1979)
| 1a | a. Gill lamellae on Ab1-6 rounded at apices | Stenonema femoratum (Say) |
| b. Ab7 gill tracheated | ||
| 1b | a. Gill lamellae on Ab1-6 truncate at apices | 2 |
| b. Ab7 gill untracheated | ||
| 2a(1b) | Posterolateral projections present on abdominal segments anterior to Ab6 | 3 |
| 2b | Posterolateral projections absent on abdominal segments anterior to Ab6 | 7 |
| 3a | Each maxillary crown < 10 (usually 0) hair setae | Stenonema mediopunctatum (McDunnough) |
| also: ventral abdominal patter consisting of dark bands extending obliquely or transversely; fore tarsal claws with or without denticles; body length of mature nymph < 10 mm | ||
| 3b | Each maxillary crown with > 10 hair setae | 4 |
| 4a(3b) | a. Ventral abdominal pattern consisting of dark bands (occasionally interrupted medially) extending transversely across the posterior margins of at least Ab5-8 sterna | 5 |
| b. 2-5 spinelike setae on maxillary crown | ||
| 4b | a. Ventral abdominal pattern without dark posterior crossbands on Ab5-8 sterna, maculations variable or absent | 6 |
| b. 2-8 spinelike setae on maxillary crown | ||
| 5a(4a) | a. Posterior band of Ab8 sternum narrowest medially, gradually widening sublaterally |
Stenonema luteum (Clemens) |
| b. Fore tarsal claws with denticles | ||
| c. Ab9 posterolateral projection shorter than on Ab8 | ||
| d. Setae sparse or lacking on outer margins of cerci | ||
| e. Armature on dorsal surfaces of fore femora often predominately of oval-shaped setae | ||
| f. Body length of mature nymph 9-10 mm | ||
| 5b | a. Posterior band of Ab8 sternum approximately the same width across most of segment | Stenonema vicarium (Walker)(in part) |
| b. Fore tarsal claws without denticles | ||
| c. Ab9 posterolateral projection as long or longer than that on Ab8 | ||
| d. Setae usually dense over much of the outer margins of cerci | ||
| e. Armature on dorsal surfaces of fore femora predominately with acute spinelike or elongate setae | ||
| f. Body length of mature nymph 10-18 mm | ||
| 6a(4b) | Ab2-7 terga with distinct crossbands on posterior 1/4 of segments forming a sharp contrast with pale areas |
Stenonema vicarium (Walker)(in part) |
| 6b | Ab2-7 not exactly as above, with posterior bands much narrower or absent | Stenonema luteum (Clemens) |
| also: Fore tarsal claws with denticles; 2-4 spinelike setae on maxillary crown; body length of mature nymph 9-10 mm | ||
| 7a(2b) | Maxillary crown < 10 (usually 0) hair setae | 8 |
| also: Mandibles with 4-8 (rarely 9) teeth on the inner margin of outer incisors; body length of mature nymphs 7-11 mm; no pale V-shaped areas on abdominal terga | ||
| 7b | Maxillary crown > 10 hair setae | 12 |
| 8a(7a) | Mesonota with conspicuous large pale spots or a complete pale band at the wing pad bases | Stenonema exiguum Traver |
| 8b | Mesonota without large pale spots or complete pale band at wing pad bases | 9 |
| 9a(8b) | Maxillary crowns with 1-8 hair setae or, if 0 hair setae, terminal abdominal sternum with a brown posterior margin | Stenonema terminatum (Walsh)(in part) |
| 9b | Maxillary crowns with 0 hair setae, and terminal abdominal sternum with a pale posterior margin | 10 |
| 10a(9b) | a. Ab4-7 with brown lateral longitudinal markings and anterior stripes or dashes extending obliquely laterad | Stenonema terminatum (Walsh)(in part) |
| b. Ab7 tergum mostly dark | ||
| 10b | a. Ab4-7 without above dark markings | 11 |
| b. Ab7 tergum variable in color | ||
| 11a(10b) | a. Ab7 tergum mostly white | Stenonema pulchelium (Walsh) |
| b. Fore tarsal claws with denticles | ||
| c. Maxillae each with 5-6 spinelike setae on crown | ||
| 11b | a. Ab7 tergum mostly dark | Stenonema terminatum (Walsh)(in part) |
| b. Fore tarsal claws with or without denticles | ||
| c. Maxillae each with 2-6 spinelike setae on crown | ||
| 12a(7b) | a. Ab7-9 with distinct V-shaped pale mark | Stenonema mexicanum integrum (McDunnough) |
| b. Maxillae each with 2-3 spinelike setae on crown | ||
| 12b | a. Ab7-9 without distinct V-shaped pale mark | 13 |
| b. Maxillae each with 3-7 (rarely 3) spinelike setae on crown | ||
| 13a(12b) | In ventral view, Ab3-8, 4-8, 5-8 or 6-8 sterna with a distinct pattern of oblique crossbars | 14 |
| 13b | Abdominal sterna without above pattern, if crescent-shaped crossbars present, then only on Ab7 and/or Ab8 | Stenonema modestum (Banks)(in part) |
| 14a(13a) | a. Fore tarsal claws not denticulate | Stenonema ithaca (Clemens and Leonard)(in part) |
| b. Crown of maxillae each with 15-35 hair setae | ||
| 14b | a. Fore tarsal claws with denticles | 15 |
| b. Crown of maxillae each with 15-50 hair setae | ||
| 15a(14b) | Crown of maxillae each with < 30 hair setae | Stenonema ithaca (Clemens and Leonard)(in part) |
| 15b | Crown of maxillae each with > 30 hair setae | Stenonema modestum (Banks)(in part) |
References
-
Bednarik AF, McCafferty WP. 1979. Biosystematic revision of the genus Stenonema (Ephemeroptera: Heptageniidae). Canadian Bulletin of Fisheries and Aquatic Sciences 201:1-73.
Page created: November 13, 2003; Last edited: November 06, 2013 (EB)