Complete Taxonomy (Neuswanger 2012, Stang 2012, and Spieth 1933):
(Domain: Eukaryota)
Kingdom: Animalia - Animals
(Subkingdom: Bilateria, Branch: Protostomia, Infrakingdom: Ecdysozoa, Superphylum: Panarthropoda)
        Phylum: Arthropoda - Arthropods
        (Subphylum: Mandibulata, Infraphylum: Atelocerata, Superclass: Panhexapoda, Epiclass: Hexapoda)
             Class: Insecta - Insects
             (Subclass: Dicondylia, Infraclass: Pterygota)
                        Order: Ephemeroptera - Mayflies
                        (Suborder: Pisciforma, Superfamily: Heptagenioidea OR previously, Oligoneuriidae)
                                Family: Isonychiidae - Brush-legged mayflies
                                         Genus: Isonychia - The root "iso-," meaning "same," conjoins with "nych," or "night," to describe a genus of organisms whose life begins and ends in one day--that is, essentially, the "same night." Paired with the species name, which stands for "two colors," this insect has its full identity...
Species: Isonychia bicolor

Identifying Synapomorphies: From the Insect Class to the Specific Epithet

Class Insecta:
    ~ Head, thorax, and abdominal segments.
    ~ Pairs of antennae and compound eyes.
    ~ Up to three ocelli, otherwise known as "simple eyes," or "eyespots."
    ~ The front, lower part of the head includes several mouthparts, which appear as long, segmented rods
        (DeWalt et al. 2010).

- Order Ephemeroptera:
    ~ Commonly known as "the mayflies," these insects hatch, molt as they progress through all of their live
        stages, mate, and die within roughly one day (Neuswanger 2012).

- Family Isonychiidae:
    ~ Only some joints and jaws carrying tiny teeth (Spieth 1933).
    ~ Two rows of long setae "filters" on the insect's midsection
            * Hence this family's reputation, "the brush-legged mayflies."
    ~ Gills on maxillae.
    ~ Trachea without a branch running up the belly side to bring oxygen to the head.
- Genus Isonychia:
More specialized structures and cross-vein patterns on wings.
    ~ Smaller anus than its close cousins possess.
    ~ Adults have 4-jointed forceps (Spieth 1933)
    ~ There are gills on the first seven abdominal segments (Speith 1933).
        * This is the primary characteristic feature which sets Isonychia  apart from all other genera!
    ~Tuft-like gill slits at the base of the front leg pair (Neuswanger 2012).
    ~"Posterior marginal bands" of a gray-black hue
        * These are present in the darkest shade in Isonychia bicolor (Kondratieff and Voshell 1984).

- Species Isonychia bicolor:
~ Have four basic body types with changes in color that varies throughout the season. The abdomen
       changes from yellow to red, while the foretarsals vary from an off-white/ cream to a dark brown
       (Kondratieff and Voshell 2010). This coloration has lead to the second half of their species name: bicolor!
    ~On their medial wing flap, there is a row of serrations (sometimes loosely referred to as "teeth").
    ~The shape of their labium and labrum (respectively, lower and upper lip) is unlike other mayfly genera.
    ~ Penes (male genitalia) are simple, consisting of a pair of pointed processes (Spieth 1933).
Have a bivoltine , seasonal life cycle that can be seen here. This is unique to the species.
            - While the size of these insects is quite large relative to other insects as a whole, the standards for size differ by cohort and time of year (in other words, which life cycle an individual has been born into). The summer and fall generation, which can be light or dark in color and are called "harperi" (for more on the details and distinctions of these two main seasonal forms, go to Reproduction and Life Cycle), range from 10-13 millimeters, while those born in the winter and spring, the "sadleri," weigh in at a heftier 15-18 mm (Kondratieff and Voshell 1984).
            - Females of both seasonal varieties are the larger gender. They are also more difficult to classify species-wise, and to do so requires extensive analysis of egg shape, color, and pattern (Kondratieff and Voshell 1984)!

Overall, classification of this species, as is the case with many branches of life known to humans, has been and remains a topic of dispute among taxonomists. Therefore, one should note that systematic naming is more of a process than something set in stone. What is presented on this page is the most current, though other versions of Isonychia bicolor's life history do exist and should be considered in order to acquire the most accurate portrait of the mayfly's synapomorphological (adaptive, evolutionary) background.


*To return to the website Table of Contents,
or for more information on the common names listed
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