Eotrechus Kirkaldy, 1902

Tran, Anh Duc, Zettel, Herbert & Sites, Robert W., 2023, Revision of the genus Eotrechus Kirkaldy (Hemiptera, Heteroptera, Gerridae), with descriptions of six new species, Deutsche Entomologische Zeitschrift 70 (1), pp. 69-111 : 69

Genus Eotrechus Kirkaldy, 1902

Eotrechus Kirkaldy, 1902: 137 (type species: Eotrechus kalidasa Kirkaldy, 1902, by monotypy).

Eotrechus : Distant (1903: 182); Matsuda (1960: 249-251); Andersen (1982: 5-8) (revision).

Diagnosis.

Body length: apterous males 5.5-10.3, macropterous males 6.7-11.6, apterous females 6.3-11.7, macropterous females 7.1-11.3. Body colouration: dorsum dark-brown, or yellowish with dark-brown markings; ventral side either dark or pale. Antennae long, slender, usually subequal to body length: segment I slightly longer than segment II and usually with 1-8 dark spines subapically (spines absent in the E. kalidasa species group); segments II and IV subequal in length; segment III shortest. Rostrum long and slender, reaching anterior third of mesosternum. Pronotal lobe: reduced in apterous form (e.g., Fig. 1 ); strongly produced in macropterous form, with rounded posterior margin (e.g., Fig. 11C ). Ratio of lengths of mesosternum: metasternum variable, around 1.7-5.3: 1.0. Scent orifice small. Fore leg variable, either moderately incrassate or slender. Hind legs longer than middle legs; hind tibia longer than or subequal to middle tibia; claws inserted at apex of tarsal segment II, with long ventral arolium. Pregenital abdominal venter of male 0.2-0.4 × body length; posterior margin of sternum VII either concave or emarginated medially. Male genitalia of variable size; pygophore usually modified, either with dense setae or with posterior projection(s) or both; paramere relatively small. Abdominal venter of female at most one-half of body length.

Remarks.

Among the genera of the subfamily Eotrechinae , only Eotrechus has claws that are inserted at the apex of tarsal segment II ( Andersen 1982). The comparative morphology and relationship between Eotrechus and other eotrechine genera have been reviewed and discussed by Andersen (1982) and Polhemus and Andersen (1984). According to these studies, Eotrechus is most closely related to Chimarrhometra .

Based on the comparative examination of morphological features among species of Eotrechus , e.g., relative lengths of the mesosternum and metasternum, structure of the fore femur, structures of the abdominal sterna, and modification of the male genitalia, we propose the classification of this genus into seven species groups, as in the Taxonomic account section below. The assumption of monophyly of each species group and the relationship among species of Eotrechus still needs to be tested by future phylogenetic analyses.

Note that E. sinensis Andersen, 1982 cannot be assigned to any species group. The only known specimen of this species is a female and was not available for this study; thus, it was not possible to assess the relationship of this species with its congeners (see Remarks for E. sinensis ).

Revised key to species of Eotrechus

1	Mesosternum clearly less than twice as long as metasternum. Fore femur slender, basal part as slender as that of other femora	2
-	Mesosternum more than twice as long as metasternum. Fore femur incrassate	4
2	Antennal segment III only slightly shorter than each other segment. Paramere slender, proximal part not clearly wider than distal part, apex narrow (Figs 4C , 5F )	E. kalidasa Kirkaldy, 1902
-	Antennal segment III distinctly shorter than other segments, at most 0.9 × the length of each other segment. Proximal part of paramere about twice wider than distal part, apex rounded	3
3	Fore leg: tarsal segment I shorter, ca. 0.7 × the length of segment II. Paramere: proximal half twice as wide as distal half, distal half stout, slightly twisted (Fig. 2C )	E. fuscus Basu, Chandra & Venkatesan, 2017
-	Fore leg: tarsal segment I longer, 1.10-1.25 × the length of segment II. Paramere: proximal third twice as wide as distal part, distal two-thirds slender, directed slightly dorsad (Figs 4F , 5E )	E. steineri sp. nov.
4	Male specimens	5
-	Female specimens [identification is more reliable with associated male specimens]	23
5	Fore femur with broad basal tubercle or with a spot of dense minute black setae. Pygophore with one caudal projection, but without posterolateral projections	6
-	Fore femur simple, without basal tubercle. Pygophore with a pair of posterolateral projections, but without caudal projection	15
6	Basal tubercle of fore femur produced into tooth-like elevation or a small nodule. Caudal projection of pygophore expanded posterolaterally	7
-	Basal tubercle of fore femur simple, without tooth-like elevation or nodule. Caudal projection of pygophore not modified as above	8
7	Basal tubercle of fore femur produced into tooth-like elevation (Fig. 15F ). Caudal projection of pygophore with concave posterior margin and two angular posterolateral tips (Fig. 15H )	E. siamensis Vitheepradit & Sites, 2007
-	Basal tubercle of fore femur with a small nodule bearing minute black setae (Fig. 17A, B ). Caudal projection of pygophore with almost straight posterior margin and two lateral lobes (Fig. 17D-F )	E. konkakinh sp. nov.
8	Pygophore produced caudally into triangular or narrowly pointed projection	9
-	Pygophore produced caudally into broad plate-like projection	12
9	Caudal projection of pygophore very long and slender, with length of projection distinctly greater than width of pygophore	10
-	Caudal projection of pygophore shorter, with length of projection clearly less than width of pygophore	11
10	Caudal projection of pygophore gradually tapering towards apex (in ventral view), evenly curved dorsad (in lateral view) (Fig. 7A-D ). Lateral process of proctiger rectangular (Fig. 7F ). Paramere elongated, length>2.0 × width (Fig. 7D )	E. petraeus Andersen, 1982
-	Caudal projection of pygophore very slender (in ventral view), strongly bent dorsad at apical part (in lateral view) (Fig. 9B, C ). Lateral process of proctiger acute, pointing posteriorly (Fig. 9D ). Paramere small and with conical apex, length ca. 1.5 × width (Fig. 9E )	E. kerberos sp. nov.
11	Pygophore: lateral tubercles less distinct; caudal projection slender, with pointed apex (Figs 12 , 13G, H ). Proctiger, in dorsal view: posterolateral tubercle indistinct, apex of proctiger rounded (Figs 12B , 13I )	E. thai sp. nov.
-	Pygophore: lateral tubercles prominent, pointing laterad; caudal projection broad, with rounded apex (Fig. 13C, D ). Proctiger, in dorsal view: posterolateral tubercle strongly swollen, apex of proctiger angular (Fig. 13E )	E. romglao Vitheepradit & Sites, 2007
12	Lateral tubercles of pygophore distinct, situated near narrowest part of pygophore	13
-	Lateral tubercles of pygophore absent or indistinct	14
13	Pygophore: with dense long and soft setae on ventrolateral surface; lateral tubercles small. Proctiger: with patch of long setae on ventrocaudal surface; posterolateral lobes small, angular	E. fansipan J. Polhemus, Tran & D. Polhemus, 2009
-	Pygophore: without dense setae on ventrolateral surface; lateral tubercles large (Fig. 14B, C ). Proctiger: without patch of long setae on ventrocaudal surface; posterolateral lobes large, rounded (Fig. 14D )	E. pingae Andersen, 1998
14	Caudal projection of pygophore about as long as wide. Posterolateral lobes of proctiger large, directed caudad, reaching median apex of proctiger (in dorsal view)	E. luaae Tran & Zettel, 2006
-	Caudal projection of pygophore clearly longer than wide (Fig. 15C, D ). Posterolateral lobes of proctiger smaller, directed posterolaterad, distinctly not reaching median apex of proctiger (in dorsal view) (Fig. 15E )	E. elongatus Vitheepradit & Sites, 2007
15	Pygophore without posterolateral projections, usually with only long setae posterolaterally	16
-	Pygophore with a pair of well-developed posterolateral projections	18
16	Fore femur with a row of four long, stiff setae on flexor side; fore tibia with a row of long, stiff setae on extensor side. Pygophore simple, not modified posteriorly, with long, soft setae	E. hygropetricus Andersen, 1982
-	Fore femur without long, stiff setae on flexor side; fore tibia without long, stiff setae. Pygophore with very dense setae or posterolaterally modified	17
17	Fore femur strongly incrassate at basal part, length ca. 4.3 × maximum width. Pygophore and proctiger with very dense, bristle-like, black setae; posterolateral processes of pygophore short, bearing a tuft of tightly packed, thick setae	E. pilicaudatus Tran & Zettel, 2006
-	Fore femur moderately incrassate, length about ca. 6.2 × maximum width. Pygophore and proctiger with sparser and shorter, soft, brownish setae; posterolateral corners of pygophore rounded or produced into small lobes, without a tuft of tightly packed, thick setae (Figs 18C, D , 19D-F )	E. boukali sp. nov.
18	Posterolateral projections of pygophore slender, simple, directed caudad, apex of projection narrowly rounded or pointed	19
-	Posterolateral projections of pygophore broad, usually flat, directed posterolaterally, apex of projection more modified	21
19	Posterolateral projections of pygophore thick, with rounded apices, and distal part swollen, covered with dense, long, bristle-like setae	E. anderseni sp. nov.
-	Posterolateral projections of pygophore tapering towards narrow apices, without long, bristle-like setae	20
20	Posterolateral projections of pygophore in lateral view with a notch on lower margin and with broader distal part (Fig. 21B )	E. longipes Andersen, 1982
-	Posterolateral projections of pygophore in lateral view without notch and with slender distal part	E. terrestris Andersen, 1982
21	Posterior margin of sternum VII with a broad, shallow median notch. Posterolateral projections of pygophore with finger-like process near apex	E. brevipes Andersen, 1982
-	Posterior margin of sternum VII deeply emarginated, length of median notch about half of the length of sternum VII. Posterolateral projections of pygophore without finger-like process	22
22	Posterolateral projections of pygophore thickened and broadened at distal part, with tubercles on both sides of each projection	E. pumat J. Polhemus, Tran & D. Polhemus, 2009
-	Posterolateral projections of pygophore plate-shaped and without such tubercles	E. vietnamensis Tran & Yang, 2006
23	Fore femur without a row of stiff setae on flexor side	24
-	Fore femur with a row of stiff setae on flexor side	27
24	Body length greater than 10.5. Sternum VII about as long as two preceding sterna combined	25
-	Body length clearly less than 8.5. Sternum VII clearly longer than two preceding sterna combined	26
25	Third rostral segment curved and swollen at base (Fig. 23B ). Tergum VIII with tuft of long, bristle-like setae on each posterolateral corner (Fig. 23C )	Eotrechus sp. A
-	Third rostral segment almost straight and not swollen at base. Tergum VIII simple, without tuft of long, bristle-like setae	E. anderseni sp. nov.
26	Sternum VII 1.2-1.3 × as long as two preceding sterna combined. Genitalia totally enclosed by tergum VIII and sternum VII, proctiger not visible in lateral view	E. brevipes Andersen, 1982
-	Sternum VII ca. 1.5 × as long as two preceding sterna combined. Genitalia not totally enclosed, proctiger visible in lateral view	E. longipes Andersen, 1982 and E. terrestris Andersen, 1982
27	Dorsal surface of head with a yellowish stripe on midline. Fore femur with 4-5 long, stiff setae on flexor side. Length of mesosternum at least 4.0 × length of metasternum	28
-	Dorsal surface of head mainly brown, without yellowish stripe on midline. Fore femur with at least nine long, stiff setae on flexor side. Length of mesosternum less than 3.6 × length of metasternum	29
28	Sternum VII ca. 1.2 × as long as two preceding sterna combined	E. vietnamensis Tran & Yang, 2006
-	Sternum VII ca. 1.6 × as long as two preceding sterna combined	E. pumat J. Polhemus, Tran & D. Polhemus, 2009
29	Tergum VIII produced posterolaterally (Figs 10G , 13F )	30
-	Tergum VIII not as above, posterior margin almost straight	31
30	Sternum VII slightly longer (ca. 1.1 ×) than two preceding sterna combined	E. romglao Vitheepradit & Sites, 2007
-	Sternum VII clearly longer (ca. 1.3 ×) than two preceding sterna combined	E. thai sp. nov. and E. kerberos sp. nov.
31	Stiff setae on flexor side of fore femur as long as greatest width of fore femur	32
-	Stiff setae on flexor side of fore femur distinctly shorter than greatest width of fore femur	33
32	Fore trochanter with a distinct row of long, stiff setae. Combined median length of sterna II to VII ca. 0.4 × body length. Sternum VII about as long as two preceding sterna combined (Fig. 19K )	E. hygropetricus Andersen, 1982
-	Fore trochanter usually with only 2-3 stiff setae (Fig. 19C ). Combined median length of sterna II to VII ca. 0.3 × body length. Sternum VII distinctly longer (ca. 1.5 ×) than two preceding sterna combined (Fig. 19J )	E. boukali sp. nov.
33	Combined median length of sterna II to VII ca. 0.4 × body length. Sternum VII ca. 1.4 × as long as two preceding sterna combined; posterior margin of sternum VII produced medially	E. sinensis Andersen, 1982
-	Combined median length of sterna II to VII less than 0.4 × body length. Sternum VII at most 1.3 × as long as two preceding sterna combined; posterior margin of sternum VII not produced medially	34
34	Pronotum without sublateral yellow markings	E. siamensis Vitheepradit & Sites, 2007
-	Pronotum with sublateral yellow markings extending from anterior part	35
35	Sublateral yellow markings of pronotum longer, about two-thirds of pronotal length. Mesonotum of apterous morph mostly yellowish on anterior half	E. konkakinh sp. nov.
-	Sublateral yellow markings of pronotum shorter, less than half of pronotal length. Mesonotum of apterous morph mainly brown	36
36	Sternum VII 1.0-1.1 × as long as two preceding sterna combined	E. luaae Tran & Zettel, 2006
-	Sternum VII ca. 1.3 × as long as two preceding sterna combined	E. elongatus Vitheepradit & Sites, 2007 and E. fansipan J. Polhemus, Tran & D. Polhemus, 2009

Taxonomic account

Eotrechus kalidasa species group

Diagnosis. Fore leg long and slender. Mesosternum short, only 1.5-1.7 × length of metasternum. Male: sternum VII shorter than two preceding sterna combined, posterior margin concave or slightly emarginated. Male genitalia: pygophore with long and slender posterolateral projections; paramere well-developed, longer than wide; proctiger with broadly rounded apex. Female: sternum VII shorter than two preceding sterna combined.

Species included. E. kalidasa Kirkaldy, 1902, E. fuscus Basu, Chandra & Venkatesan, 2017, and E. steineri sp. nov.

Figures

Figure 1. In-situ photographs of Eotrechus. A. E. vietnamensis, apterous male, from Ha Giang Province, Vietnam; B. E. konkakinh sp. nov., apterous male, from Gia Lai Province, Vietnam.

Figure 2. Eotrechus fuscus. A. Pygophore, lateral view; B. Proctiger, dorsal view; C. paramere, lateral view; D, E. Posterior part of abdomen, female, dorsal and lateral views (A, B. Same scale; D, E. Same scale).

Figure 4. Eotrechus kalidasa, specimen from India (A-C) and E. steineri sp. nov. (D-F). A, D. Pygophore, lateral view; B, E. Proctiger, dorsal view; C, F. Paramere, lateral view (A, B, D, E. Same scale; C, F. Same scale).

Figure 5. Eotrechus steineri sp. nov. (A-E) and E. kalidasa (F). A. Fore leg of male; B. Abdomen of male, ventral view; C, D. Posterior part of abdomen of female, dorsal and lateral views; E, F. Paramere, lateral view (B-D. Same scale; E, F. Same scale).

Figure 7. Eotrechus petraeus, holotype. A, B. Genitalia, ventral and lateral views; C, D. Pygophore, lateral and dorsal views; E, F. Proctiger, lateral and dorsal views. (A, B. Same scale; C-F. Same scale).

Figure 9. Eotrechus kerberos sp. nov., holotype. A. Left fore leg, ventral view; B, C. Pygophore, lateral and dorsal views; D. Proctiger, dorsal view; E. Paramere, lateral view (B-D. Same scale).

Figure 10. Eotrechus kerberos sp. nov. A-F. Holotype; A. Abdomen of male, ventral view (excluding genitalia); B, C, D. Pygophore, ventral, lateral, and dorsal views; E, F. Proctiger, lateral and dorsal views; G, H. Posterior part of abdomen of female, dorsal and lateral views (B-F. Same scale; G, H. Same scale).

Figure 11. Eotrechus thai sp. nov., habitus. A. Apterous male (from Doi Inthanon. Thailand); B. Apterous female (from Doi Inthanon); C. Macropterous female (from Doi Suthep, Thailand).

Figure 12. Eotrechus thai sp. nov., male genitalia. A. Lateral view; B. Dorsal view; C. Ventral view.

Figure 13. Eotrechus romglao (A, C-E) and E. thai sp. nov. (B, F-I). A, B. Right fore leg, ventral view; C, G. Genital capsule (pygophore and proctiger) of male, lateral view; D, H. Pygophore, dorsal view; E, I. Proctiger, dorsal view; F. Abdominal apex of female, dorsal view (A, B. Same scale; C-E, G-I. Same scale).

Figure 14. Eotrechus pingae, holotype. A. Right fore leg; B, C. Pygophore, dorsal and lateral views; D. Proctiger, dorsal view (B-D. same scale).

Figure 15. Eotrechus elongatus (A-E) and E. siamensis (F-I), males. A, B, F. Right fore leg (A, F. Ventral view; B. Dorsal view); C, G. Genital capsule, lateral view; D, H. Pygophore, dorsal view; E, I. Proctiger, dorsal view (A, B, F. Same scale; C-E, G-I. Same scale).

Figure 17. Eotrechus konkakinh sp. nov. A, B. Right fore leg of male, dorsal and ventral views; C. Abdomen of male, ventral view; D. Genitalia, lateral view; E, F. Pygophore, ventral and dorsal views; G. Proctiger, dorsal view; H, I. Posterior part of abdomen of female, dorsal and ventral views (A-C, H, I. Same scale; D-G. Same scale).

Figure 18. Eotrechus boukali sp. nov. A, B. Habitus; A. Apterous male; B. Apterous female; C. Pygophore, dorsal view; D. Proctiger, dorsal view (A, B. Same scale; C, D. Same scale).

Figure 19. Eotrechus boukali sp. nov. (A-J) and E. hygropetricus (K). A. Right fore leg of male; B. Abdomen of male, ventral view (excluding genital capsule); C. Right fore leg of female; D, G. Genital capsule, lateral view; E, H. Genital capsule ventral view; F. Genital capsule, dorsal view (D-F. Paratype from location 22 ° 19.113 ' N, 94 ° 28.518 ' E; G, H. Paratype from location 22 ° 19.094 ' N, 94 ° 28.823 ' E); I, K. Abdomen of female, lateral view; J. Abdomen of female, lateral view (A, B, I-K. Same scale; D-H. Same scale).

Figure 21. Eotrechus longipes, holotype. A. Right fore leg; B. Abdominal apex, ventral view.

Figure 23. Eotrechus sp. A, macropterous female. A. Habitus; B. Head in lateral view showing rostrum; C. Terga VI-VIII, dorsal view.