Geostiba Thomson, 1858

Gusarov, Vladimir I., 2002, A revision of Nearctic species of the genus Geostiba Thomson, 1858 (Coleoptera: Staphylinidae: Aleocharinae), Zootaxa 81, pp. 1-88: 5-14

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http://doi.org/ 10.5281/zenodo.155701

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scientific name

Geostiba Thomson, 1858
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Geostiba Thomson, 1858  ( Figs. 1­340View FIGURES 1 ­ 7View FIGURES 8 ­ 17View FIGURES 18 ­ 20View FIGURES 21 ­ 25View FIGURES 26 ­ 28View FIGURES 29 ­ 33View FIGURES 34 ­ 37View FIGURES 38 ­ 50View FIGURES 51 ­ 56View FIGURES 57 ­ 60View FIGURES 61 ­ 71View FIGURES 72 ­ 76View FIGURES 77 ­ 80View FIGURES 81 ­ 93View FIGURES 94 ­ 99View FIGURES 100 ­ 107View FIGURES 108 ­ 119View FIGURES 120 ­ 125View FIGURES 126 ­ 133View FIGURES 134 ­ 145View FIGURES 146 ­ 151View FIGURES 152 ­ 156View FIGURES 157 ­ 168View FIGURES 169 ­ 173View FIGURES 174 ­ 177View FIGURES 178 ­ 186View FIGURES 187 ­ 192View FIGURES 193 ­ 196View FIGURES 197 ­ 203View FIGURES 204 ­ 212View FIGURES 213 ­ 218View FIGURES 219 ­ 229View FIGURES 230 ­ 246View FIGURES 247 ­ 252View FIGURES 253 ­ 261View FIGURES 262 ­ 266View FIGURES 267 ­ 270View FIGURES 271 ­ 283View FIGURES 284 ­ 288View FIGURES 289 ­ 293View FIGURES 294 ­ 305View FIGURES 306 ­ 309View FIGURES 310 ­ 315View FIGURES 316 ­ 320View FIGURES 321 ­ 326View FIGURES 327 ­ 335View FIGURE 336View FIGURE 337View FIGURE 338View FIGURE 339View FIGURE 340)

Evanystes Gistel, 1856: 387  (Type species: Aleochara circellaris Gravenhorst, 1806  , by subsequent designation (Blackwelder 1952 )).

Geostiba Thomson, 1858: 33  (Type species: Aleochara circellaris Gravenhorst, 1806  , by monotypy).

Sipalia: Fenyes, 1920: 249  (non Mulsant & Rey, 1853; non Fauvel, 1902 a) (as valid genus in tribe Myrmedoniini  Thomson, 1867).

Geostiba: Fenyes, 1920: 249  (as synonym of Sipalia  ).

Sonomota: Fenyes, 1920: 249  (as subgenus of Sipalia  ).

Sipalia: Bernhauer & Scheerpeltz, 1926: 599  (as valid genus in subtribe Athetina  Casey, 1910).

Geostiba: Bernhauer & Scheerpeltz, 1926: 599  (as synonym of Sipalia  ).

Sonomota: Bernhauer & Scheerpeltz, 1926: 599  (as subgenus of Sipalia  ).

Sipalia: Scheerpeltz, 1951: 166  (as valid genus).

Evanystes: Blackwelder, 1952: 163  (as valid genus).

Geostiba: Blackwelder, 1952: 163  (as synonym of Evanystes  ).

Geostiba: Benick & Lohse, 1974: 111  (as valid genus in tribe Callicerini  Lohse, 1969).

Geostiba: Seevers, 1978: 126  (as valid genus in subtribe Geostibina Seevers, 1978).

Evanystes: Seevers, 1978: 126  (as synonym of Geostiba  ).

Glossola: Seevers, 1978: 126  (non Fowler 1888) (as synonym of Geostiba  ).

Sonomota: Seevers, 1978: 128  (as subgenus of Geostiba  ).

Geostiba: Lohse & Smetana, 1988: 270  (as valid genus).

Geostiba: Ashe  in Newton, Thayer, Ashe & Chandler, 2000: 371 (as valid genus in subtribe Geostibina).

Evanystes: Ashe  in Newton, Thayer, Ashe & Chandler, 2000: 371 (as synonym of Geostiba  ). Glossola: Ashe  in Newton, Thayer, Ashe & Chandler, 2000: 371 (non Fowler 1888) (as synonym of Geostiba  ).

Sonomota: Ashe  in Newton, Thayer, Ashe & Chandler, 2000: 371 (as subgenus of Geostiba  ). (Other references for Palaearctic Geostiba  are omitted)

Diagnosis. Geostiba  can be distinguished from other athetine genera by the combination of the following characters: parallel­sided body; ligula divided into two separate but close lobes ( Figs. 8­10View FIGURES 8 ­ 17); pronotum with microsetae directed posteriorly along the midline of the disc (Type VI or V, Benick & Lohse 1974) ( Fig. 20View FIGURES 18 ­ 20); pronotal macrosetae short; pronotal hypomera fully visible in lateral view; mesotibia with short median macroseta; metatarsal segment 1 longer than segment 2; one empodial seta. Most species of Geostiba  are wingless, have shortened elytra and reduced eyes.

Geostiba  differs from the species of Atheta Thomson, 1858  with similar pronotal pubescence and short elytra in having the ligula divided into two separate lobes.

Geostiba  differs from Tropimenelytron Pace, 1983  in having contiguous mesocoxae and the ligula divided into two separate lobes.

Geostiba  differs from Alpinia Brundin, 1948  in having the ligula divided into two separate lobes.

Geostiba  is similar to Ousipalia Gozis, 1886  in having the ligula divided into two separate lobes, but in Geostiba  these lobes are contiguous while in Ousipalia  they are widely separated.

Description. Length 1.7­3.2 mm. Body from dark brown to yellow, parallel­sided.

Head as wide as long; eyes 1 / 2 to 1 / 10 as long as temples or absent; infraorbital carina absent. Antennal article 2 longer than article 3, 4 subquadrate or transverse, 5­10 transverse, last article as long as 9 and 10 combined, without coeloconic sensilla ( Figs. 16­17View FIGURES 8 ­ 17). Labrum ( Figs. 1, 3View FIGURES 1 ­ 7) transverse, with straight anterior margin. Adoral surface of labrum (epipharynx) as in Figs. 2, 4View FIGURES 1 ­ 7. Mandibles ( Figs. 5­7View FIGURES 1 ­ 7) symmetrical and broad, right mandible with a small medial tooth; ventral molar area without patches of denticles (400 x). Maxilla ( Figs. 12­14View FIGURES 8 ­ 17) with galea extending beyond apex of lacinia; apical lobe of galea covered with numerous fine and short setae; apical quarter of lacinia with row of closely spaced spines, middle portion produced medially and covered with numerous setae. Maxillary palpus as in Fig. 12View FIGURES 8 ­ 17. Labium as in Figs. 8 ­10, 15View FIGURES 8 ­ 17; labial palpi with three articles; ligula divided into two separate but close lobes; medial area of prementum with 1­2 pores and 0­ 10 pseudopores, lateral areas with 2­3 pores and single spinose pore. Hypopharyngeal lobes as in Fig. 11View FIGURES 8 ­ 17. Mentum ( Fig. 15View FIGURES 8 ­ 17) with anterior margin concave.

Pronotum subquadrate or slightly transverse, broadest slightly in front of middle, sides broadly rounded; anterior margin convex; anterior and posterior angles rounded; posterior margin convex; surface covered with microsetae directed posteriorly in midline, posteriorly or obliquely posteriorly in lateral areas ( Fig. 20View FIGURES 18 ­ 20) (Type VI or V, Benick & Lohse 1974); macrosetae short; hypomera fully visible in lateral view. Posterior margin of elytra straight. In few species wings fully developed, in most species wings shorter than elytra or absent. Meso ­ metasternum as in Figs. 18­19View FIGURES 18 ­ 20, mesosternal process long and wide, extended about 1 / 2 length of mesocoxal cavities, metasternal process short or not outlined (in wingless species), posterior margin of mesocoxal cavities complete or interrupted; mesocoxae contiguous. Mesotibia with short median macroseta (not longer than tibial width). Tarsal segmentation 4­5 ­ 5; metatarsal segment 1 longer than segment 2. One empodial seta present.

Abdominal terga 3­5 with moderate transverse basal impressions. Tergum 7 1.2­1.3 times as long as tergum 6. Puncturation on terga 6­7 sparser than on terga 3­5. Female sternum 8 ( Figs. 32­33View FIGURES 29 ­ 33) with row of apical microsetae (as in other Athetini  ).

Male secondary characters absent or include some of the following: impression along pronotal midline, medial tubercle or extending lobe at posterior margin of pronotum, tubercle or carina near scutellum and/or impression on each elytron, 1­2 medial tubercles or carinae on tergum 7, tubercles or carinae on tergum 8.

Median lobe of aedeagus in ventral view narrows apically ( Figs. 34 ­35View FIGURES 34 ­ 37, 57­ 58View FIGURES 57 ­ 60, 100­ 101View FIGURES 100 ­ 107). Internal sac with 1­2 pairs of diverticula ( Figs. 21 ­22, 24­28View FIGURES 21 ­ 25View FIGURES 26 ­ 28, 42View FIGURES 38 ­ 50, 64View FIGURES 61 ­ 71, 85View FIGURES 81 ­ 93, 112View FIGURES 108 ­ 119). Copulatory piece with narrow apical process ( Figs. 23View FIGURES 21 ­ 25, 27View FIGURES 26 ­ 28, 39View FIGURES 38 ­ 50, 62View FIGURES 61 ­ 71). Medial lamellae narrow ( Figs. 21 ­22, 24­28View FIGURES 21 ­ 25View FIGURES 26 ­ 28, 40, 47View FIGURES 38 ­ 50).

Synonyms. Gistel (1856) proposed the generic name Evanystes  to include eight species but did not designate the type species or provide the description. For a long time the name Evanystes  was ignored by staphylinid taxonomists who used the name Geostiba  or Sipalia  . The species included by Gistel in Evanystes  made it a very broadly defined group, somewhat equivalent to Homalota  of early staphylinid taxonomists. Blackwelder (1952) made a very unfortunate choice when he designated Aleochara circellaris  as a type species of Evanystes  . As a result the name Geostiba  was made a junior objective synonym of Evanystes  . To preserve the stability of nomenclature the majority of taxonomists working on the group continued to use the name Geostiba  . Because Blackwelder (1952) and a few other entomologists used the name Evanystes  as valid, the requirements of the Code (§23.9.1, ICZN 1999) for preservation of Geostiba  as a valid name are not met. An application to preserve the use of Geostiba  and suppress the use of Evanystes  has been submitted to the Commission on Zoological Nomenclature (Case 3239) by Gusarov.

Mulsant and Rey (1853) proposed Sipalia  as a subgenus of Homalota Mannerheim, 1830  , and included six species (three of them are now placed in Leptusa Kraatz, 1856  , two in Geostiba  , and one in Octavius Fauvel, 1873  ). Fauvel (1902 a) validly designated Homalota difformis Mulsant & Rey, 1853  as the type species of Sipalia Mulsant & Rey, 1853  . Because at that time Homalota difformis  was already a member of Leptusa  ( Kraatz 1856; Bernhauer 1900), Sipalia  replaced Leptusa  ( Fauvel 1902 b). Evidently Fauvel’s designation was overlooked by most workers. Leptusa  continued to be used for the genus that included the type species of Sipalia  ( Bernhauer 1905; Reitter 1909; Bernhauer & Scheerpeltz 1926; Scheerpeltz 1966, etc.) while Sipalia  was used for Geostiba  ( Sainte­Claire Deville 1906; Reitter 1909; Bernhauer & Scheerpeltz 1926; Scheerpeltz 1934; etc.). Lohse (1974) and Benick and Lohse (1974) brought attention to the synonymy of Sipalia  and Leptusa  and since then the name Geostiba  was almost universally used as valid. A more detailed discussion of the name Sipalia  can be found in the application to preserve the use of Leptusa  and suppress the use of Sipalia  , submitted to the Commission on Zoological Nomenclature (Case 3256) by Gusarov and Herman.

The generic name Glossola Fowler, 1888  is listed by Seevers (1978) and Newton et al. (2000) as a synonym of Geostiba  . This is incorrect: Glossola  should be listed as a synonym of the genus Aloconota Thomson, 1858  because the type species of Glossola  ( Homalota gregaria Erichson, 1839  ; by monotypy) is a synonym of the type species of Aloconota  ( Tachyusa immunita Erichson, 1840  ; by monotypy) which is regarded by Seevers (1978, p. 110) and Newton et al. (2000, p. 368) as a valid genus.

Lohse and Smetana (1988) placed the name Sonomota Casey, 1911  (described as a subgenus of Sipalia  ) in synonymy with Microdota Mulsant & Rey, 1873  , a subgenus of Atheta Thomson, 1858  . This synonymy was overlooked by Newton et al. (2000) who list Sonomota  as a subgenus of Geostiba  . The type of Sipalia lippa Casey 1911  (the type species of Sonomota  , by original designation) has the ligula divided into two lobes only at the apex as in other species of Atheta  . Atheta lippa  is similar to some other species of Atheta  with short elytra ( A. turpicula ( Casey, 1910)  described from Colorado, A. pacifica ( Casey, 1910)  from California and British Columbia, A. hesperica ( Casey, 1910)  from California and A. cornelli Pace, 1997  described from Oregon) and may represent a distinct lineage within Atheta  . This group will be revised elsewhere.

Discussion. To find additional characters for species identification and to establish the relationships of Geostiba  to the other genera of Athetini  a special study of the internal sac of the aedeagus has been undertaken. The details of the internal sac of Nearctic species of Geostiba  have not been illustrated adequately in published drawings ( Lohse & Smetana 1988; Pace 1997). The internal sac has been studied both in retracted and everted position in some Palaearctic species and in all Nearctic species described in this paper. Comparison of the details of the internal sac in Geostiba  with those in some species of Atheta  and Philhygra  ( Brundin 1944; Sawada 1972; Gusarov unpublished) demonstrates that in all three genera the internal sac has the same parts. The terms used by Brundin and Sawada can be applied to the homologous parts in the internal sac of Geostiba  . The illustrations of the internal sac in retracted, partially and completely everted state show position of these parts ( Figs. 197­202View FIGURES 197 ­ 203, 204­ 211View FIGURES 204 ­ 212).

To evert the internal sac, the aedeagus was placed in potassium hydroxide solution in which the soft tissue was partially dissolved. After that, the aedeagus was transferred into a drop of water. While the water was diffusing into the aedeagus it was often possible to evert the internal sac by gently pressing (dorsally) with an insect pin at the basal part of the median lobe. This apparently simulates the natural evertion of the internal sac during copulation when the muscles connecting the ventral and dorsal sides of the base of the aedeagus contract. To complete the evertion a thin but blunt minuten can be introduced inside the median lobe basally and then the partially everted internal sac can be pushed further out. After the internal sac has been everted, the aedeagus can be transferred back into potassium hydroxide solution for complete removal of soft tissue.

The copulatory piece (the term used by Sawada (1972); equivalent to the Ductuslamelle in Brundin (1944 )) is the internal sac sclerite with the opening of ejaculatory duct in it (CP, Figs. 197­200View FIGURES 197 ­ 203, 206­ 207, 209 ­ 210View FIGURES 204 ­ 212). This sclerite is present in many tribes of the Aleocharinae  , including the tribe Athetini  . In Geostiba  the copulatory piece narrows apically into a pointed process ( Figs. 23View FIGURES 21 ­ 25, 39View FIGURES 38 ­ 50, 62View FIGURES 61 ­ 71). The suspensoria (the term used by Sawada (1972); equivalent to the S­förmigen Stäbe or hakenförmigen Bildungen of Brundin (1944 )) are two structures connected laterally to the basis of the copulatory piece (S, Figs. 197, 199 ­ 200View FIGURES 197 ­ 203). In Geostiba  the suspensoria are poorly sclerotized, with a group of tiny denticles at the apex.

The medial lamellae (Mediallamellen of Brundin (1944 )) are two sclerotized structures attached to the U­shaped plate (U­ förmige Platte, Brundin 1944). When the sac is everted these structures are located on the ventral surface of the sac, proximal of the copulatory piece. In some groups of Athetini  , the medial lamellae and the U­shaped plate are large and act to guide the copulatory piece while the internal sac is being everted. In Geostiba  the medial lamellae are thin and narrow (ML, Figs. 197­198, 201View FIGURES 197 ­ 203, 208­210View FIGURES 204 ­ 212, 21­22, 24­ 28View FIGURES 21 ­ 25View FIGURES 26 ­ 28).

In Geostiba  the ventral side of the everted internal sac proximal of the medial lamellae has one or two pairs of diverticula which may be an autapomorphy of the genus. In Palaearctic G. (s. str.) circellaris  , G. (Sipalotricha) infirma (Weise, 1878)  , G. (Sibiota) padana (Weise, 1878)  and G. (Sibiota) oertzeni (Eppelsheim, 1888)  there is one pair ( Figs. 21 ­22, 24­ 28View FIGURES 21 ­ 25View FIGURES 26 ­ 28), in all native Nearctic species of Geostiba  there are two pairs of diverticula (DD, PD, Figs. 197­199, 202View FIGURES 197 ­ 203, 206, 210View FIGURES 204 ­ 212). The distal pair is more sclerotized than the proximal pair. A study of different Palaearctic lineages of Geostiba  is required to confirm the presence of diverticula in all Geostiba  and to establish homology between one of the two pairs of diverticula in the Nearctic species and the single pair in the few examined Palaearctic species.

While trying to evert the internal sac in different specimens of Geostiba  , it was relatively easy to achieve what may be just a partially everted state. In this state, the lateral wall of the sac, which in many species has striate microsculpture (LW, Figs. 198View FIGURES 197 ­ 203, 209View FIGURES 204 ­ 212), forms a flange encircling the hollow from which the copulatory piece and medial lamellae protrude. When the internal sac is retracted into the median lobe, the striate lateral wall of the sac is clearly visible (LW, Figs. 204­205View FIGURES 204 ­ 212). Because the lateral wall is folded into three layers it often looks like a sclerite. This structure is shown schematically in some drawings by Lohse and Smetana (1988: Figs. 4View FIGURES 1 ­ 7, 12View FIGURES 8 ­ 17, 19View FIGURES 18 ­ 20, 26View FIGURES 26 ­ 28) and in one drawing by Pace (1997: Fig. 13View FIGURES 8 ­ 17). The shape of the folds and the microsculpture of the internal sac wall are stable within species and can be used for identification, although it is important to bear in mind that when internal sac starts to evert the position and the shape of the folds may change. In a few specimens I succeeded in everting the internal sac completely ( Figs. 199View FIGURES 197 ­ 203, 210View FIGURES 204 ­ 212, 234, 242View FIGURES 230 ­ 246) and revealed the apical membranous portion of the sac which have tiny scattered denticles in some species. Additional study is necessary to determine whether the sac is completely or partially everted during copulation.

Some populations of Southern Appalachian Geostiba  are very similar and it is difficult to decide whether they represent distinct species or forms of the same species. When two forms are sympatric and found in the same sample they are considered to represent different species. The situation with allopatric forms is more difficult. Even when a certain gap between two allopatric forms exists, additional consideration is needed to decide how to reflect this difference taxonomically. In this paper the difference between G. nimbicola  and G. nebuligena  is used as a criterion for assigning species rank to closely related allopatric forms. Both species are known from the Great Smoky Mountains massif and both were collected on Clingmans Dome, however never in the same sample or on the same date. The two species can be distinguished only by the shape of the apex of the median lobe of aedeagus ( Figs. 100­107View FIGURES 100 ­ 107, 152­ 156View FIGURES 152 ­ 156). Whenever I encountered the gap on the same scale between two allopatric forms, I assigned to them species rank.

Some characters previously used in keys to distinguish species of Geostiba  ( Lohse & Smetana 1988; Pace 1997) are found to be of limited utility. For example, the microsculpture of the abdominal tergum 7 is similar in all native Nearctic species. In the basal portion of the tergum the microsculpture consists of transverse meshes, while in the apical portion it consists of isodiametric or even elongate meshes ( Figs. 56View FIGURES 51 ­ 56, 99View FIGURES 94 ­ 99, 125View FIGURES 120 ­ 125, 151View FIGURES 146 ­ 151, 192View FIGURES 187 ­ 192, 218View FIGURES 213 ­ 218). I did not count the number of ommatidia in the eyes but instead compared eye length to temple length.

Kingdom

Animalia

Phylum

Arthropoda

Class

Insecta

Order

Coleoptera

Family

Staphylinidae

Loc

Geostiba Thomson, 1858

Gusarov, Vladimir I. 2002
2002
Loc

Geostiba:

Newton 2000: 371
2000
Loc

Evanystes:

Newton 2000: 371
Newton 2000: 371
2000
Loc

Sonomota:

Newton 2000: 371
2000
Loc

Evanystes

Gistel 1856: 387
Loc

Geostiba

Thomson 1858: 33
Loc

Sipalia:

Fenyes 1920: 249
Loc

Geostiba:

Fenyes 1920: 249
Loc

Sonomota:

Fenyes 1920: 249
Loc

Sipalia:

Bernhauer 1926: 599
Loc

Geostiba:

Bernhauer 1926: 599
Loc

Sonomota:

Bernhauer 1926: 599
Loc

Sipalia:

Scheerpeltz 1951: 166
Loc

Evanystes:

Blackwelder 1952: 163
Loc

Geostiba:

Blackwelder 1952: 163
Loc

Geostiba:

Benick 1974: 111
Loc

Geostiba:

Seevers 1978: 126
Loc

Evanystes:

Seevers 1978: 126
Loc

Glossola:

Seevers 1978: 126
Loc

Sonomota:

Seevers 1978: 128
Loc

Geostiba:

Lohse 1988: 270