principles of systematics and nomenclature general system and phylogeny of insects systematics of Ephemeroptera



(the dictionary of wrongly used terms)


The easiest way not to make errors in morphological descriptions, is to learn insect morphology and morphology of selected mayfly taxa, using the following publications:


Kluge N.J. 1994. Pterothorax structure of mayflies (Ephemeroptera) and its use in systematics. // Bulletin de la Société entomologique de France 99(1): 41–61. (terms connected with skeleton and musculature of imaginal and subimaginal mesothorax)


Êëþãå Í.Þ. 2003. Îá ýâîëþöèè è ãîìîëîãèè ãåíèòàëüíûõ ïðèäàòêîâ íàñåêîìûõ. // Òðóäû ÐÝÎ, 74: 3–16.  
Kluge N.J. 2003. About evolution and homology of genital appendages of insects. // Trudy Russkogo Entomologicheskogo Obshestva / Proceedings of the Russian Entomological Society, 74: 316 (in Russian). (homology of genitals in Ephemeroptera)


Kluge N. 2004. The phylogenetic system of Ephemeroptera. // Kluwer Academic Publishers. p. i–xiii + 1–442 (morphological terms)

Kluge N.J. 2005. Larval/pupal leg transformation and a new diagnosis for the taxon Metabola Burmeister, 1832 = Oligoneoptera Martynov, 1923. // Russian Entomological Journal (2004) 13(4): 189–229. (term protopteron)


Kluge N.J. 2010. Paradoxical moulting process in Orthezia urticae and other coccids (Arthroidignatha, Gallinsecta). // Zoosystematica Rossica 19(2): 246–271. (terms ultimolarva, penultimolarva, ultimonympha, etc.)


Kluge N.J. & Novikova E.A. 2011. Systematics of the mayfly taxon Acentrella (Ephemeroptera, Baetidae), with description of new Asian and African species. // Russian Entomological Journal 20 (1): 1–56. (terms cladoendesis, microlepides, unistyliger, penial bridge, gonovectis)


Snodgrass R.E. 1935. Principles of insect morphology. / New York, London: McGraw-Hill Book Company: 1–667.







Many authors, when indicate dimension of a mayfly taxon, indicate all together its length of body, length and width of wings, length of cerci, length of paracercus, and and these or that other dimensions, sometimes indicating range for each dimension. Actually, each animal taxon has a certain range of dimensions and certain proportions (or a range of proportions); dimension and proportion are quite different things, which should not be mixed. For example, Bae & McCafferty report for the genus Potamanthus «Length of body 8.0-14.0, forewings 7.714.5, ...». Actually no one mayfly can have body length 8.0 mm with forewing length 14.5 mm, as well as body length 14.0 mm with forewing length 7.7 mm.
filaments The widely used term «caudal filaments» becomes shorter, if reduce it either to the original cauda (Linnaeus 1758), or caudulae (Kirby & Spense 1824), or caudalii (Kluge 1989, 2004). The additional word «filaments» is unnecessary here. Amond three caudalii, the two lateral ones are termed cerci (Kirby & Spense 1826), and the median one is termed paracercus.Structure of caudalii.
forceps segments Some authors call gonostyli of male mayflies «forceps» and count their segments in such a way, that in Baetidae and some other mayflies with deeply divided styliger, they take for the 1st segment of «forceps» a lateral portion of styliger (which is thickened, because includes the muscle running to the base of gonostylus), while in mayflies with more integral styliger, they take for the 1st segment of «forceps» this or that proximal portion of gonostylus. Originally, the term «forceps» was used for cerci of earwigs (Kirby & Spense 1826). Gonostyli of mayflies are not homologous to forceps; for correct homology of gonostyli, styliger and their parts, see Kluge 2003, 2004, Kluge & Novikova 2011. .Genitalia of mayflies.


gills The term «gill» can be used for organ of any origin, which serves for underwater respiration. If the organ has clearly known homology, it should be named by its own term. Tergalii of mayfly larvae can either serve, or not serve as gills, but their homology is out of doubt, so they should be named by their own term, not «gills». Some authors not only use the term «gills» for tergalii, but also believe that tergalii of mayfly larvae are either similar, or homologous to pre-spiracular gills of some other aquatic insect larvae, that leads them to wrong scientific conclusions. .Difference between gills and tergalii.

penis lobes

Some authors use the word combination «penis lobes» instead of the word «penis». Actually, the whole male genital organ of mayflies is named penis (plural: penes); it often consists of unpaired proximal part and a pair of distal lobes (see Fig. C), or is completely divided into left and right lobes. .Genitalia of mayflies.


 see: dimension
spine Some authors wrongly use the word «spines» for thick setae (bristles). Actually, spine is a «multicellular external process», while seta is a «unicellular external process» (Snodgrass 1935: 69), independently of their thickness.
styliger plate Some authors use this combination of two words. Maybe it means «plate of styliger»? In this case, what other part of styliger, besides the plate, do they know? I have no idea. .Genitalia of mayflies.


tarsal claw From any textbook, one can learn that the appendage named by Latin term unguis (English claw) belongs not to tarsus, but to pretarsus, which is quite different part of the insect leg. Probably the authors, who write the wrong combination «tarsal claw», are needed to distinguish it from some other claw, but I have no idea, whom which one. .Legs of insects.
tarsus 1st, 2nd, 3rd, 4th, 5th. Each insect has only thee pairs of legs, and their tarsi can be called fore, middle and hind ones. Each insect leg never has more than one tarsus. Probably, the authors who have found up to five «tarsi», mean not tarsi, but tarsal segments, or tarsomeres. .Legs of insects.
terminal filament Some authors, instead of the generally accepted term paracercus, write «terminal filament». Actually, paracercus is not a filament, but has peculiar structure and musculature (Kluge 2004). These authors believe that each mayfly has only one «terminal filament», but three «caudal filaments» (see above). This non-understandable terminology proceeds from the old and wrong theory, according to which insect cerci are regarded to be derivatives of paired appendages, while paracercus was regarded to be something different. Actually, all three appendages on the end of tenth abdominal segment are equally «terminal» and «caudal», and have the same origin. Their common name is either caudulae  (Kirby & Spense 1826), or caudalii (Kluge 1989, 2004). .Structure of caudalii.
wing bud, wing pad, wing case, wing fundament, wing rudiment

The terms «wing bud» (Snodgrass 1935), «wing pad», «wing case», «wing fundament» are used in English texts, because English language lacks a word equal to Latin «rudiment», German «Anlage» or Russian «çà÷àòîê». The Latin term «rudiment» is so often wrongly used instead of «vestige» (Lat. «vestigium»), that it can lead to confusion if use it in its correct meaning. 

The special term «protopteron» has been introduced for the peculiar outgrows of larval meso- and metanotum, which serve as ontogenetic precursors of imaginal wings (Kluge 2005). In some respect protopteron is a rudiment of wing (in the original meaning of the word «rudiment»), because in course of subsequent development its hypoderm becomes the hypoderm which produces cuticle of the imaginal wing. At the same time, protopteron is not poorly a wing rudiment, because its cuticle, shaded at each molt and not inherited by the wing, has peculiar morphological features absent in the wing.