Maccaffertium bednariki - (McCafferty, 1981)
a flat-headed mayfly
Synonym(s): Stenonema bednariki McCafferty, 1981
Taxonomic Status: Accepted
Related ITIS Name(s): Maccaffertium bednariki (McCafferty, 1981) (TSN 698212)
Unique Identifier: ELEMENT_GLOBAL.2.109032
Element Code: IIEPH40080
Informal Taxonomy: Animals, Invertebrates - Insects - Mayflies
Kingdom Phylum Class Order Family Genus
Animalia Mandibulata Insecta Ephemeroptera Heptageniidae Maccaffertium
Genus Size: D - Medium to large genus (21+ species)
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Concept Reference
Concept Reference: Purdue University Department of Entomology (W.P. McCafferty ed.) 1995. Last updated 9 July 2002. Mayfly Central- The Mayflies of North America. Online. Available:
Concept Reference Code: N95PUR01EHUS
Name Used in Concept Reference: Stenonema bednariki
Taxonomic Comments: Formerly placed in the genus Stenonema (see Wang and McCafferty, 2004).
Conservation Status

NatureServe Status

Global Status: G2G4
Global Status Last Reviewed: 11Dec2003
Global Status Last Changed: 11Dec2003
Rounded Global Status: G3 - Vulnerable
Reasons: This is a valid species that appears to be restricted to the south-central highlands extending from the Cumberland Plateau in Kentucky to the Ozarks of Missouri and Oklahoma. Thus it is expectd to be found possibly also in very high quality streams in such areas as the mounainous regions of Arkansas and the Shawnee Hills of southern Illinois. It is assigned a preliminary ranking, because it has only been known since 1981.
Nation: United States
National Status: N2N4 (11Dec2003)

U.S. & Canada State/Province Status
Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
United States Kentucky (S2), Missouri (S3), Oklahoma (S4?)

Other Statuses

NatureServe Global Conservation Status Factors

Number of Occurrences:  
Number of Occurrences Comments: McCafferty et al. (1997) cited occurrences in Oklahoma in Mayes Co.

Other NatureServe Conservation Status Information

U.S. States and Canadian Provinces

Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
Color legend for Distribution Map
Endemism: endemic to a single nation

U.S. & Canada State/Province Distribution
United States KY, MO, OK

Range Map
No map available.

U.S. Distribution by County Help
State County Name (FIPS Code)
KY Breathitt (21025), Casey (21045), Clay (21051), Larue (21123), Leslie (21131), Marion (21155), Nelson (21179), Owsley (21189), Pulaski (21199)*
MO Barry (29009), Bollinger (29017), Carter (29035), Christian (29043), Crawford (29055), Dent (29065), Douglas (29067), Iron (29093), Laclede (29105)*, Madison (29123), McDonald (29119), Oregon (29149), Reynolds (29179), Ripley (29181), Shannon (29203), St. Clair (29185), Ste. Genevieve (29186), Taney (29213), Texas (29215), Washington (29221), Webster (29225)*, Wright (29229)*
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
05 North Fork Kentucky (05100201)+, Middle Fork Kentucky (05100202)+, South Fork Kentucky (05100203)+, Upper Green (05110001)+, Upper Cumberland-Lake Cumberland (05130103)+*, Rolling Fork (05140103)+
07 Meramec (07140102)+, Big (07140104)+, Upper Mississippi-Cape Girardeau (07140105)+, Whitewater (07140107)+
08 Upper St. Francis (08020202)+*
10 Harry S. Missouri (10290105)+, Upper Gasconade (10290201)+*, Big Piney (10290202)+
11 James (11010002)+, Bull Shoals Lake (11010003)+, Upper Black (11010007)+, Current (11010008)+, Eleven Point (11010011)+, Elk (11070208)+
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
Non-Migrant: N
Locally Migrant: N
Long Distance Migrant: N
Riverine Habitat(s): CREEK
Special Habitat Factors: Benthic
Habitat Comments: In Kentucky, larvae were taken in an open canopy area of small fourth order streams, predominantly on slab rubble and gravelly substrates. The gradient was moderate and the water quality very good (P. McCafferty, personal communication, December 2003).
Economic Attributes Not yet assessed
Management Summary Not yet assessed
Population/Occurrence Delineation
Group Name: Mayflies

Use Class: Not applicable
Minimum Criteria for an Occurrence: Occurrences are based on some evidence of historical presence or current presence of single or multiple specimens ideally with evidence of on-site breeding (including nymphs, subimago adults, and imago adults) at a given location with potentially breeding habitat. Evidence is derived from reliable published observation or collection data; unpublished, though documented (i.e. government or agency reports, web sites, etc.) observation or collection data; or museum specimen information. A photograph may be accepted as documentation of an element occurrence for adults only (nymphs and subimagos are too difficult to identify in this manner) provided that the photograph shows diagnostic features that clearly delineate the species from other species with similar features. The families, Ameletidae, Baetidae, Caenidae, Ephemerellidae, Heptageniidae, Leptohyphidae, Leptophlebiidae, and Siphlonuridae, are particularly difficult to identify from a photograph alone; geographic information in almost always an additional requirement. Sight records, though valuable, should not be accepted as the basis for new element occurrences. Instead, such records should be utilized to further study an area to verify the element occurrence in that area.
Separation Barriers: Within catchments there are likely no significant barriers to movement of adults between microhabitats, with even extensive sections of inappropriate waterway or major obstructions to flow being readily traversed by adults during dispersal following emergence.
Separation Distance for Unsuitable Habitat: 3 km
Separation Distance for Suitable Habitat: 3 km
Alternate Separation Procedure: None
Separation Justification: Mayflies (Order Ephemeroptera) are an order of insects with an immature larval stage that is entirely aquatic. Larvae usually undergo numerous molts and the length of larval existence is usually three to six months but can be as short as two weeks (some Baetidae, Leptohyphidae, and Caenidae) or as long as two years [Hexagenia limbata (Serville, 1829), in some cold climates] (Edmunds and Waltz, 1996). Following the larval molts, mayflies enter a unique life stage among living insects called the subimago. The subimago is a winged, though sexually immature stage, that is typically found perched on shoreline vegetation and lasts from four minutes to 48 hours (directly correlated with the lifespan of the adult) (Edmunds and Waltz, 1996). Females of some North American species are known to mate and lay eggs as a subimago (e.g. Tortopus, Campsurus, Ephoron, and Serratella) (Edmunds and Waltz, 1996).

The rate of mayfly dispersal is limited in the larval stage by drainage systems, and in adult stages by relatively short life spans and weak flying ability of gravid females (Berner and Pescador, 1988; McCafferty, 1998). Adults of most species live only two hours to three days (some less than 90 minutes) (Edmunds and Waltz, 1996; W.P. McCafferty, personal communication). Both subimagos and adults tend to remain along banks at emergence sites (Brittain, 1990; Knopp and Cormier, 1997). Dispersal at the population level has been little studied. At the species level, McCafferty (1998) claimed past dispersal of mayflies is reflected by both wide-ranging species resulting from diffusion dispersal (range expansion of individual species) and geographically radiating species diversity from secular migration (dispersal of a lineage via expansion with accompanying division of species ranges leading to geographic speciation) with the latter type spread over time resulting from a series of vicariant events on a small scale. Although passive dispersal (i.e. drift) is too unpredictable to consider when accurately assigning separation distances (see Stewart and Szczytko, 1983, for drift rates in m for a few species), it is worth noting that Humphries (2002) found that upstream movement in Baetis rhodani (Pictet) in the United Kingdom is sufficient to compensate for numerical losses in populations because of drift.

Separation distances (unsuitable and suitable) have been set at three km based upon several life history characteristics that limit occurrences to a short distance from the area of emergence, among them: (1) life cycles of adults and subimagos are extremely short compared to other aquatic insects; (2) adults (and particularly subimagos) tend to remain along the banks of emergence sites with males gathering in swarms to intercept females for mating; (3) flying ability (particularly for adult females) is not strong with dispersal rarely exceeding a few km (Malmqvist, 2000).

Date: 18Oct2004
Author: Cordeiro, J.
Population/Occurrence Viability
U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed

Zoological data developed by NatureServe and its network of natural heritage programs (see Local Programs) and other contributors and cooperators (see Sources).

  • McCafferty, W. P., R. K. Heth and R. D. Waltz. 1997a. The Ephemeroptera of Spring Creek, Oklahoma, with remarks on notable records. Entomological News 108:193-200.

  • Purdue University Department of Entomology (W.P. McCafferty ed.) 1995. Last updated 9 July 2002. Mayfly Central- The Mayflies of North America. Online. Available:

  • Wang, T.-Q. and W.P. McCafferty. 2004. Heptageniidae (Ephemeroptera) of the world. Part I: phylogenetic higher classification. Transactions of the American Entomological Society, 130(1): 11-45.

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