Stenacron
| Stenacron | |
|---|---|
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Insecta |
| Order: | Ephemeroptera |
| Suborder: | Schistonota |
| Superfamily: | Heptagenoidea |
| Family: | Heptageniidae |
| Genus: | Stenacron |
Stenacron is a genus of mayflies in the family Heptageniidae.
The genus of Stenacron (Jensen 1974) is a vastly understudied and largely misunderstood genus. From P A Lewis (1974) "The Taxonomy and Ecology of Stenonema Mayflies" forward, very little to nothing has been done with this genus in the field and in laboratories.
Although the larva can be found in many different conditions they have some basic and preferred requirements. All samples I have collected regardless of the form or species are found near the bank. They tend to cling to the underside of rocks that are a minimum of 8 X 8 inches and 2 inches thick. The larger the rock the greater the population per rock. They are seldom found in the faster riffle waters but more so at the slower moving banks. Typically with a water depth of no less than 3 inches and up to 16 inches deep. The most important factor is the waters "DO" (dissolved oxygen). Stenacron can live in waters that are not moving and low in (DO). In rearing experiments I have found that they can survive and hatch in a bucket with little oxygen added for up to 4 days. However, in a watershed they do prefer a stable and moderate DO in which greater populations will occur. Lewis (1974) showed that the form (Stenacron interpunctatum / heterotarsale) historically carried an EBI (Empirical Biotic Index) rating of a level (7) showing a high tolerance level to pollution's both Toxic and Organic. (under updates)
Dr J R Traver, the second author of the Biology of a Mayfly (1935), erected three distinct groups in the genus Stenonema in 1933. The interpunctatum group later became the genus Stenacron. Steven L Jensen in 1974 erected the genus name Stenacron.
There are currently 16 forms that reside in this genus and only 7 of the forms carry a valid species status. The other remaining forms have all been synonymized into the valid species Stenacron interpunctatum. These forms are referred to as Stenacron interpunctatum / interpunctatum not as Stenacron interpunctatum.(Say 1839)
Thomas Say, the god father of American entomology, first documented the species interpunctatum in 1839 in Indiana from 20 halotypes and 14 paratypes. Hagan (1861) confirms and expands the geographical range of the species with the collection of others in Virginia that concurred with Says (1839) halotypes.
Here is a list of the currently valid species as of 2014:
Below are the synonym forms that make up the interpunctatum complex.
New larva morphological information has been found! Before we review these findings let me quote a few important statements from previous authors on this genus to set the pace.
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Wikipedia