Genus  Marpissa  C.L.Koch, 1846

The genus, based on Marpissa muscosa (Clerck,1758) as type species, is characterized by flattening of the lateral surface of palpal cymbium in males and by complicated coils of epigyne in females.
The genus as outlined here, consisits of two distinct groups of species, often considered to be separate genera.
The Marpissa proper (M.dybowski, M.pulla and other) has broad, flattened abdomen, bulbs rounded with embolus encircling it, cymbium very broad and usually rounded.
The second group of species (M.elongata, M.magister, M.pulchra and others) is characterized by elongate narrow abdomen, short embolus, epigyne consisting of two posteriorly opened grooves separated by a median ridge; the canals make compact knots.
That group has been often named Hyctia Simon, 1876[type species Hyctia nivoyi (Lucas,1846)], 
Mithion Simon,1884 (type species Mithion semiargenteus Simon,1884), Icidella Strand in Bosenberg et Starnd,1906 [type species Icidella interrogationis Bosenberg et Strand,1906=Marpiisa magister (Karsch,1879)(?)].
Usage of two first of these names has some merits, however, the relationship of Hyctia nivoyi to Marpissa needs further research.
The best known South European species of Mithion - Mithion canestrinii (Ninni in Canestrini et Pavesi,1868) is certainly congeneric with Marpissa magister and other related species.
Both groups are certainly very closely related and do form a continuous chain of forms in North America and Palaearctic.
Calling them a single genus stresses these relationships although may create troubles in writing identification keys.
As the type species of the genus Mithion Simon,1884 - Mithion semiargenteus Simon,1884 belongs in fact to genus Thyene Simon,1885(Proszynski 1987) there are no more species left in Mithion.
That name should become a synonym of Theyne, which contains numerous speciemen three continents in spite of one year priority of Mithion.
Other choice - remaining all Thyene species would cause to much nomenclatorical confusion.
Very useful comparison of external characters in Marpissa magister, Marpissa elongata, Marpissa pulchra (marked No.3 but not named) and a new species, for males and females, as well as ventral abdominal markings, outlines of epigyne and lateral view of the palpal organ give Chikuni and Yaginuma (1976: 33-34).
  

Species  Marpissa ibarakiensis  sp.n.

Material. 1 female holotypus - Japan: Ibaraki, 25.VI.1966, leg.Y.Suganami- coll.T.Yaginuma.

 The specimen resembles Marpissa pulchra in general appearance but differs in larger size.
 The abdomen differs in total absence of golden scales - however this may be an artefact and needs confirmation on fresh specimens.
 There are large dark brown lateral spots identical in location and size as in Marpissa pulchra, separated by spots of bald surface with sparse remnants of whitish scales.
 Median streak of white scales, extended anteriorly by white setae;
it is followed laterally surfaces of abdomen whitish with one row of small and sparse grey dots, posteriorly two shorter rows od same dots.
 Ventrally three intensely brownish black median streaks along abdomen fused in front of spinnerets.
 Similar streaks in Marpissa pulchra are light greyish wuth brownish shade, in one specimen separated by two rows of light dots.
 The most important difference between <arpissa ibarakiensis and Marpissa pulchra lies in internal structure of epigyne, the external differences are ambiguous.
 While spermathecae in Marpissa pulchra consists of heavily sclerotized entangled loops, forming extrenally a single compact body, Marpissa ibarakiensis has much simpler canal forming single loop, with two (in other side three) curious spherical chambers attached laterally (figs.106-111).
 The poor preservation of specimen and its weakly sclerotized epigyne calls for further study of fresh material.


  
(from Bohd. and Prosz.,1987)