Tropimenelytron Pace 1983
Creators: name: Gusarov, Vladimir I.
Publisher: name: Zenodo
Year: 2002
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Staphylinidae
Tropimenelytron

description: Tropimenelytron Pace, 1983 (Figs. 1­21, 35­64)
Tropimenelytron: Scheerpeltz, 1955: 171 (first record but unavailable name). Tropimenelytron Pace, 1983: 187.
Pelioptera (Tropimenelytron): Pace, 1991: 839.
Pelioptera (Tropimenelytron): Assing, 2000: 1000. Tropimenelytron: Assing, 2001: 168.
Diagnosis. Tropimenelytron can be distinguished from other aleocharine genera by the combination of the following characters: parallel­sided body; ligula with wide base, split apically (Fig. 9); pronotum subquadrate, with microsetae directed posteriorly along the midline of the disc (Type V, Benick & Lohse 1974) (Fig. 12); pronotal macrosetae moderately long; pronotal hypomera fully visible in lateral view; mesocoxae separated; medial macroseta of mesotibia as long as tibial width; tarsal formula 4­5­5; metatarsal segment 1 about as long as segment 2; one empodial seta; apical process of median lobe of aedeagus straight or slightly bent ventrally at the very apex (in lateral view; Figs. 41, 51, 61); spermatheca without umbiculus (Figs. 39, 49, 59).
Tropimenelytron differs from Geostiba Thomson, 1858 in having ligula with wide base, separated mesocoxae and different shape of aedeagus and spermatheca.
Tropimenelytron differs from Pelioptera micans Kraatz, 1857 (the type species of Pelioptera Kraatz, 1857) in the following characters: first segment of labial palpus with seta absent (present in P. m i c a n s); prementum with three asetose pores (two in P. micans), spermatheca without umbiculus; copulatory piece with short apical process (with very long flagellum­like apical process in P. m i c a n s) (see discussion below).
Tropimenelytron differs from Earota Mulsant & Rey, 1874 by smaller and narrower body; first segment of labial palpus lacking seta; shorter mesosternal process; incomplete infraorbital carina, less transverse pronotum and different shape of aedeagus and spermatheca.
Tropimenelytron differs from Seeversiella Ashe, 1986 in having pronotal pubescence of type V (Benick & Lohse 1974); ligula with wide base; separated mesocoxae; posterior angles of male tergum 3 not extended as spines, and copulatory piece of aedeagus without long flagellum.
Description. Length 2.5­3.7 mm. Body parallel­sided, from uniformly brownish yellow to reddish brown with dark brown head and abdominal segment 6, and brown appendages.
Head slightly longer than wide; eyes small, temples 1.5­3 times as long as eyes; infraorbital carina short, not reaching posterior margin of eye. Antennal article 2 longer than article 3, articles 4­10 transverse (Fig. 14). Labrum (Fig. 1) transverse, anterior margin concave. Adoral surface of labrum (epipharynx) as in Fig. 2. Mandibles (Figs. 3­ 5) broad, right mandible with very small medial tooth; dorsal molar area with velvety patch consisting of tiny denticles (visible at 400x). Maxilla (Figs. 6­8) with galea extending slightly beyond apex of lacinia; apical lobe of galea covered with numerous fine and short setae; apex of lacinia with row of closely spaced spines, middle portion covered with numerous setae. Maxillary palpus with four segments (Fig. 6). Labium as in Figs. 9­ 11; labial palpi with three segments (Fig. 9), first segment of labial palpus lacking seta (Fig. 9); ligula with wide base, split apically; medial area of prementum without pores or pseudopores, lateral areas with 3 asetose pores and single setose pore. Hypopharyngeal lobes as in Fig. 10. Mentum (Fig. 11) with slightly concave anterior margin, medial area with numerous pores.
Pronotum (Fig. 12) subquadrate, broadest at apical third, narrows posteriorly or with subparallel lateral margins; anterior margin straight, posterior margin convex; surface covered with microsetae directed posteriorly in midline, posteriorly and obliquely laterally in lateral areas (Type V, Benick & Lohse 1974); macrosetae moderately long; hypomera fully visible in lateral view. Meso­ and metasternum as in Fig. 13, mesosternal process short and wide, extended about 1/4 length of mesocoxal cavities, metasternal process about 1/3 length of mesocoxal cavities; mesosternum and mesosternal process not carinate medially; relative lengths of mesosternal process: isthmus: metasternal process in ratio of about 3:4:4; mesocoxal cavities margined posteriorly; mesocoxae separated. Medial macroseta of mesotibia as long as tibial width. Tarsal segmentation 4­5­5; metatarsal segment 1 about as long as segment 2 (Fig. 15). One empodial seta present. Wings fully developed (in Nearctic species). Posterior margin of elytra straight.
Abdominal terga 3­5 with moderately transverse basal impression. Tergum 7 ­ 1.1 times as long as tergum 6. Punctation on terga 6­7 slightly sparser than on terga 3­5. Tergum 7 with white palisade fringe.
Male secondary sexual characters include longitudinal carina along anterior half of sutural margin of each elytron, tiny medial knob at posterior margin of tergum 3, small medial knob at apical third of tergum 4, short medial carina in front of anterior margin of tergum 7 and uneven posterior margin of tergum 8 (Fig. 35). Some (smaller) males may lack these features altogether and externally look like females. Median lobe of aedeagus narrows apically (in parameral view; Figs. 40, 50, 60), apex straight or slightly bent ventrally (in lateral view; Figs. 41, 51, 61). Parameres with two long and two short macrosetae (Figs. 44, 54, 64). Copulatory piece of internal sac with short apical process and lateral denticles near the base of process (CP; Figs. 18, 20). Medial lamellae (in parameral view) broad (ML; Figs. 17, 20­21). Spermatheca without umbiculus, with thick C­shaped distal portion and thin proximal portion which may form 1­2 coils (Figs. 39, 49, 59)
Type species. Geostiba tuberiventris Eppelsheim in Leder, 1879 by original designation.
Gender. The name Tropimenelytron ends in a Greek word “ ” transliterated into Latin without other changes and therefore takes the neutral gender (Article 30.1.2 of the Code; ICZN 1999). Because a species name must agree in gender with the generic name with which it is combined (Article 31.2.1) when G. tuberiventris is placed in Tropimenelytron the correct spelling is T. tuberiventre.
Discussion. Although originally described as a separate genus (Pace 1983) Tropimenelytron was subsequently (Pace 1991) downgraded to subgeneric rank within the genus Pelioptera. Pace (1991) argued that Pelioptera, Tropimenelytron and Geostibida have “almost identical” ligula, but in Pelioptera mesocoxae are more widely separated. Pace considered this similarity in ligula sufficient to include Tropimenelytron and Geostibida in Pelioptera as subgenera.
Pelioptera micans Kraatz, 1857 (Figs. 23­24, 27­29; Fig. 9 in Sawada 1980), the type species of Pelioptera, differs from T. tuberiventre and T. americanum Gusarov, sp. n. in the following characters: first segment of labial palpus with seta present (Fig. 23) (absent in Tropimenelytron: Fig. 9) and equidistant from setae b and; prementum with two asetose pores (Fig. 23) (three in Tropimenelytron: Fig. 9), spermatheca with umbiculus (Fig. 9, O in Sawada 1980) (without umbiculus in Tropimenelytron: Figs. 39, 49, 59), copulatory piece with very long apical process (flagellum­like; Fig. 29) (with short apical process in Tropimenelytron: Figs. 16, 18, 19­20). Considering the above differences between the examined species of Tropimenelytron (including the type species of the genus) and the type species of Pelioptera I do not regard their similarity in the shape of ligula to be sufficient to include Tropimenelytron in Pelioptera. In this paper I consider Tropimenelytron to represent a genus separate from Pelioptera, pending a detailed examination of related genera and subgenera and analysis of their relationships.
My examination of three species of Pelioptera (Figs. 22­34) and comparison of the drawings and descriptions published by Sawada (1977, 1980, 1982, 1987, 1989) demonstrate that the species currently assigned to Pelioptera often have very different structures of internal sac (cf. Figs. 29, 32, 34 and Figs. 10, K; 11, I; 12, J in Sawada 1980) and mesometathorax (Figs. 24­26). This may indicate that some species currently assigned to Pelioptera are not related and should not be congeneric with the type species of the genus. This problem requires further study and it is briefly discussed at the end of this paper.
In his key to subgenera of Pelioptera, Pace (1991) listed two characters to allow separation between Tropimenelytron and Geostibida: the difference in the shape of spermatheca (S­shaped in Geostibida and semicircular in Tropimenelytron) and the length of elytra (shorter than pronotum in Geostibida and longer than pronotum in Tropimenelytron). Unfortunately, these characters are not reliable. The shape of the proximal portion of spermatheca varies even among closely related species. For example, in T. americanum (Fig. 39) this portion is longer than in two other Nearctic species (Figs. 49, 59) and the spermatheca can be described as S­shaped. In many groups of Aleocharinae the length of elytra may be subject to variation even within the same species (see for example Muona 1991; Assing 1999). The specimens with well developed wings have longer elytra, while in wingless specimens the elytra are shorter. In many groups of aleocharines the species or populations restricted in their distribution to limited areas in the mountains often loose the ability to fly, have reduced wings and shorter elytra in comparison to their more widespread relatives in the plain. Clearly the length of elytra alone is not a sufficient character to separate subgenera of Pelioptera.
Pace himself is not consistent in applying these two characters to separate Tropimenelytron and Geostibida. For example, in T. nepalense Pace, 1985 a (Fig. 45 in Pace 1985a) and T. parbatense Pace,1987 a (Fig. 47 in Pace 1987a) (both assigned to Pelioptera (Tropimenelytron) in Pace 1991) the spermatheca is no less S­shaped than in G. himalayiensis Pace, 1984 (Fig. 108 in Pace 1991; assigned to Pelioptera (Geostibida) in Pace 1991). In P. (G.) problematica Pace, 1991 the elytra are both described (p. 849 in Pace 1991) and illustrated (Fig. 113 in Pace 1991) as being longer than pronotum, but nevertheless the species is placed in the subgenus Geostibida and not Tropimenelytron. In T. parbatense (Fig. 46 in Pace 1987a) elytra are illustrated as being shorter than pronotum, but in Pace 1991 this species is placed in the subgenus Tropimenelytron and not Geostibida. Some species assigned by Pace to Geostibida lack both diagnostic characters of Geostibida. For example, in P. (G.) eremita Pace, 1998 elytra are longer than pronotum (Fig. 133 in Pace 1998) and spermatheca is not S­shaped (Fig. 134 in Pace 1998).
Examination of Pace’s description of G. himalayiensis Pace, 1984 (type species of Geostibida) and description of additional species included by Pace in Geostibida (Pace 1984, 1985a, 1991, 1998) demonstrates that Geostibida is an artificial group which includes those species of Tropimenelytron (G. himalayiensis Pace, 1984; G. major Pace, 1984; G. annapurnensis Pace, 1985 a) which have short elytra, and some unrelated species (which should be reassigned to other genera) with the same type of pronotal pubescence (P. (G.) lii Pace, 1998; P. (G.) kowloonensis Pace, 1998; P. (G.) eremita Pace, 1998 and probably P. (G.) problematica Pace, 1991). A revision of the type of Geostibida is necessary to formally synonymize the name with Tropimenelytron.
The genus Tropimenelytron is being reported from North America for the first time.
description: Published as part of Gusarov, Vladimir I., 2002, A revision of Nearctic species of the genus Tropimenelytron Pace, 1983 (Coleoptera: Staphylinidae: Aleocharinae), a new genus for North America, pp. 1-24 in Zootaxa 114 on pages 3-11, DOI: 10.5281/zenodo.155753