Stenus canaliculatus, Gyllenhal, 1827

Ryvkin, Alexandr B., 2012, New species and records of Stenus (Nestus) of the canaliculatus group, with the erection of a new species group (Insecta: Coleoptera: Staphylinidae: Steninae), European Journal of Taxonomy 13, pp. 1-62 : 50-52

Key to the Palaearctic species of the canaliculatus group

1. Front with deep longitudinal impressions and high median elevation in between. Seventh abdominal tergite varnish shining, without ground-sculpture between punctures. Puncturation of pronotum and elytra fairly deep and coarse, average diameter of punctures on pronotum larger than basal cross of antennal segment 3. Disk of pronotum with deep longitudinal furrow rather broad and not lineshaped throughout. Internal tooth of each mandible shifted distally, directed mediodorsally of the main plane. Abdominal sternite 9 of both males and females (valvifera) with posterolateral teeth very short. Aedeagus small (see Fig. 7K ). 2.8–3.7 mm ……………………………………………… ……………………………………………………[ melanopus group] melanopus ( Marsham, 1802)

– If front with deep longitudinal impressions and 7 th abdominal tergite between punctures without regular ground sculpture, puncturation of pronotum very fine and dense with average diameter of punctures distinctly smaller than basal cross of antennal segment 3. Longitudinal median furrow of pronotum more or less deep but always long, line-shaped. Internal tooth of each mandible placed a little before the middle, directed only slightly dorsally of the main plane. Abdominal sternite 9 of both males and females (valvifera) with posterolateral teeth normally developed (see Fig. 5 A–E). Aedeagus large ………………………………………………………………[ canaliculatus group] 2

2. Front with distinct lateral impressions and median elevation in between …………………………3

– Front feebly convex or feebly concave, with median elevation and lateral depressions rather vague or entirely absent ……………………………………………………………………………8

3. Median elevation of front broad and knob-like. Puncturation of pronotum very fine and dense, average diameter of punctures distinctly smaller than basal cross of antennal segment 3. Disk of abdominal tergite 7 without regular ground sculpture or with reticulation very feeble and vague. Aedeagus as in Fig. 1E . 3.3–4.5 mm ……………………………………………………… labilis Erichson, 1840

– Median elevation of front ridge-shaped, angular in its cross section, flanked by broader and less sharp lateral impressions. Puncturation of pronotum coarser, average diameter of punctures about as large as or larger than basal cross of antennal segment 3 ………………………………………4

4. Apical abdominal tergites without ground sculpture. For aedeagus, see Puthz 2006 (fig. 4). 2.9–4.0 mm ………………………………………………………………………… immigratus Puthz, 2006 – At least tergites 7–10 distinctly reticulated …………………………………………………………5

5. Elytral suture about 1/4–1/5 longer than pronotum. Aedeagus as in Fig. 7 C–H. 4.0– 4.7 mm ………………………………………………………………………… latipennis J. Sahlberg, 1880

– Elytral suture not more than l/7 longer than pronotum ……………………………………………6

6. Elytral suture a bit shorter than pronotum.Aedeagus as in Figs. 6A , 7A . 4.0– 4.6 mm … delitor sp. nov.

– Elytral suture distinctly longer than pronotum ……………………………………………………7

7. Elytra more than 1/4 broader than head. Puncturation less coarse, much more regular; interspaces between punctures along the midline of anterior visible tergites distinctly wider than average diameter of punctures. Aedeagus as in Fig. 2E . 3.4–4.0 mm …………… confusus J. Sahlberg, 1876

– Elytra by 1/4–1/5 broader than head. Puncturation much coarser, distinctly irregular; interspaces between punctures along the midline of anterior visible tergites smaller than average diameter of punctures. Aedeagus as in Fig. 7B . 3.9–4.4 mm ……………………………… illusor Ryvkin, 1987

8. Elytra not longer than pronotum, nearly as broad as head. Abdominal tergites with very dense and deep ground-sculpture. Aedeagus as in Fig. 2C, D . 3.5–4.7 mm (the latter value for specimens with the abdomen extended) …………………………………… illotulus Puthz, 1972

– Elytra longer than pronotum, broader than head …………………………………………………9

9. Front as a whole feebly concave, with median elevation very vague, nearly flat, situated below internal margin level of eye; the upper surface except abdominal tergite 10 without ground sculpture. For aedeagus, see Puthz, 1987 (Abb. 1). 3.3–3.7 mm ………………………… shogun Puthz, 1987

– If front as a whole concave, at least abdominal tergites 7–8 with evident ground sculpture ……10

10. Front with median elevation and lateral depressions rather feeble but evident. Median parts of anterior abdominal tergites with puncturation very small, scattered, and shallow. For aedeagus, see Renkonen, 1935 (fig. 1). 3.0– 3.8 mm …………… vinnulus Casey, 1884

– Front with median elevation entirely absent or, occasionally (in S. nitens Stephens, 1833 ), represented by narrow, smooth longitudinal strip ………………………………………………11

11. Elytra with fairly small and dense puncturation. Anterior margin of labrum with a small median notch ………………………………………………………………………………………………12

– Elytra with puncturation larger and more or less sparse. Anterior margin of labrum without distinct median notch, at most feebly sinuate …………………………………………………15

12. Pronotum 1/7–1/8 longer than broad. Aedeagus as in Fig. 3A, B . 3.2–3.9 mm (the latter value for specimens with abdomen extended) ………………………………………… alopex sp. nov.

– Pronotum not, or only a little, longer than broad …………………………………………………13

13. Entire body with ground sculpture more or less visible. Aedeagus as in Fig. 3D . 3.0– 4.5 mm (the latter value for the American specimen with abdomen extended, the maximum value for Palaearctic specimens known to me: 4.3 mm) ……………………… canaliculatus Gyllenhal, 1827

– At least median part of abdominal tergites 3–7 without traces of microsculpture ………………14

14. Elytra between punctures with ground sculpture throughout. Aedeagus as in Fig. 4A, B . 4.0 mm (with abdomen extended) ………………………………………………… canosus sp. nov.

– Elytra between punctures with ground sculpture mainly in humeral impressions and near suture. Aedeagus as in Fig. 4C, D . 2.8–3.7 mm (the latter value for specimen with abdomen extended) ………………………………………………………………………… canalis sp. nov.

15. Middle of front punctured much sparser than lateral parts, occasionally with a small longitudinal strip or spot broader than the average diameter of punctures. Elytra only a bit (l/14th to l/15th) broader than head, being punctured larger and sparser. Aedeagus as in Fig. 1 A–D. 3.4–4.0 mm (the latter value for specimens with the abdomen extended) ………………… nitens Stephens, 1833

– Front with puncturation more regular, without evident smooth strips or spots. Elytra l/7 to l/10 broader than head, being smaller and denser punctured. Aedeagus as in Fig. 2A, B . 3.1–4.1 mm (the latter value for specimens with the abdomen extended) ……………… raddei Ryvkin, 1987

Figures

Fig. 7. ♂ copulative structures. A–I, K: Aedeagus, ventral view. J: Abdominal sternite 9. A. Stenus (Nestus) delitor sp. nov. (holotype). B. S. (N.) illusor Ryvkin, 1987 (Russia: Amur Area: Angelokit River). C–H: S. (N.) latipennis J. Sahlberg, 1880. C. (Russia: SW Taimyr: Ladannakh Lake). D. (Russia: Taimyr: Kotuy River). E. (Russia: Putorana: Ayan Lake). F–G. (Russia: Evenkia: Kruten’kiy Stream). H. (Russia: Magadan Area: ‘Aborigen’). I–J. S. (N.) sphaerops Casey, 1884 (U.S.A.: New York: Albany Co.). K. S. (N.) melanopus Marsham, 1802 (Ukraine: Odessa Area: Krinichnoye). – Scales = 0.1 mm.

Fig. 5. ♂ copulative structures. A–E: Abdominal sternite 9. A. Stenus (Nestus) latipennis J. Sahlberg, 1880 (Russia: Krasnoyarsk Territory: Mirnoye). B. S. (N.) illusor Ryvkin, 1987 (Russia: Magadan Area: 2 km W of Splavnaya). C. S. (N.) delitor sp. nov. (holotype). D. S. (N.) canosus sp. nov. (holotype). E. S. (N.) canalis sp. nov. (holotype). F. S. (N.) caseyi Puthz, 1972 (U.S.A.: Michigan: Berrien Co.). Aedeagus, ventral view. – Scales = 0.1 mm.

Fig. 1. – A–D: Stenus (Nestus) nitens Stephens, 1833: ♂ genitalia, ventral view. A–B: (Russia: Moscow Area: Gorenki). C–D: (Russia: Evenkia: Stolbovaya River). A, C. Aedeagus. B, D. Apical part of median lobe. – E. S. (N.) labilis Erichson, 1840: ♂ (Russia: S Yamal: nr. Salekhard). Aedeagus, ventral view. – Scales = 0.1 mm.

Fig. 6. Aedeagus, ventral view. A. Stenus (Nestus) delitor sp. nov. (holotype). B. S. (N.) sphaerops Casey, 1884 (U.S.A.: New York: Albany Co.). – Scales = 0.1 mm.

Fig. 2. – A–B: Stenus (Nestus) raddei Ryvkin, 1987: ♂ (Russia: Magadan Area: Sibit-Tyhellakh). A. Aedeagus, ventral view. B. Apical part of aedeagus, ventral view. – C–D: S. (N.) illotulus Puthz, 1972: ♂ (Russia: Amur Area: Zeyskiy Nature Reserve). C. Aedeagus, ventral view. D. Apical part of aedeagus, ventral view. Right paramere removed. – E. S. (N.) confusus J. Sahlberg, 1876: ♂ (Russia: Kalinin Area: Putilovo). Aedeagus, ventral view. – Scales = 0.1 mm.

Fig. 3. – A–C: Stenus (Nestus) alopex sp. nov.: ♂. A. Aedeagus, ventral view (holotype). B. Apical part of aedeagus, ventral view (holotype). C. Abdominal sternite 9 (paratype). – D–E: S. (N.) canaliculatus Gyllenhal, 1827: ♂. D. Aedeagus, ventral view (Russia: Rostov Area: Nedvigovka). E. Abdominal sternite 9 (Russia: Taimyr: Maymecha River). – Scales = 0.1 mm.

Fig. 4. – A–B: Stenus (Nestus) canosus sp. nov.: ♂ (holotype). A. Aedeagus, ventral view. B. Apical part of aedeagus, ventral view. – C–D: S. (N.) canalis sp. nov.: ♂ (holotype). C. Aedeagus, ventral view. D. Apical part of aedeagus, ventral view. [Note that the difference in shape of the apical lobe compared to that in C is due to the level of magnification.] – Scales = 0.1 mm.