Hemicrepidius Germar, 1839

Etzler, Frank E., 2020, A Revision of the Genus Hemicrepidius Germar, 1839 (Coleoptera: Elateridae) of the New World, with Comments on Global Classification, The Coleopterists Bulletin (mo 18) 74, pp. 1-126 : 14-24

publication ID	https://doi.org/ 10.1649/0010-065X-74.mo18.1
publication LSID	lsid:zoobank.org:pub:E8A1F6BE-934A-41D1-8211-90DE1FD565BF
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treatment provided by	Carolina
scientific name	Hemicrepidius Germar, 1839
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Hemicrepidius Germar 1839: 212 ; Leng 1920: 170; Schenkling 1927: 413; Becker 1979a: 407. Type species: Hemicrepidius thomasi Germar , by monotypy.

Pedetes Kirby 1837: 145 (not Pedetes Illiger, 1811 , Mammalia), in part (see Becker 1956a: 26; Becker 1974: 713). Type species: Elater obscurus Linnaeus, 1758 , by original designation. This Linnaean species is now considered a valid species in Agriotes Eschscholtz, 1829 View in CoL (see Becker 1956a, 1974 for full list of usage).

Asaphes Kirby 1837: 146 View in CoL (not Asaphes Walker, 1834 View in CoL , Hymenoptera View in CoL ) (described as a subgenus of Pedetes ). Type species: Pedetes (Asaphes) ruficornis Kirby, 1837 , by monotypy.

Heterathous Reitter 1905: 32 (described as a subgenus of Athous ). Type species: Athous sanguinicollis Frivaldszky, 1892 , by monotypy.

Pseudathous Méquignon 1930: 95 (described as a subgenus of Athous ). Type species: Elater hirtus Herbst, 1784 , by original designation. As subgenus of Athous: Leseigneur 1972: 195 . As a subgenus of Hemicrepidius: Baba and Kishii 1957: 69 . [not exhaustive]

Miwacrepidius Ôhira 1962: 263. Type species: Athous subcyaneus Motschulsky, 1866 .

Yukara Kishii 1962: 21 . Type species: Athous inornatus Lewis, 1894 , by monotypy. Return to synonymy.

Medakathous Kishii 1964: 17 (described as a subgenus of Hemicrepidius ). Type species: Athous jactatus Lewis, 1894 , by monotypy. Return to synonymy.

Diagnosis. Hemicrepidius can be distinguished from all other Elateridae by the following combination of characters: Head with frontal carina medially proximal to posterior edge of labrum, not extended anteriorly as “shelf”, so fronto-clypeal region narrow or obsolete medially (fcr, Fig. 4b View Fig ); posterior margin of pronotum with antescutellar notch (asn, Fig. 4h View Fig ); pronotosternal suture not grooved or expanded anteriorly; tarsomeres 2 and 3 with ventro-apical membranous lobes, tarsomeres 1 and 4 also with relatively smaller ventro-apical membranous lobes in most ( Figs. 5a, b View Fig ), ventroapical membranous lobe on 1 or 4 reduced or absent in some (tarsal lobe formulas 1–4, 1–3 or 2–4); parameres of aedeagus with preapical expansions (cf. Fig. 11d View Fig ); and female internal genitalia with vagina bearing two lateral, roughly triangular sclerotized patches composed of parallel linear sclerites with minute tubercles in interspaces between linear sclerites ( Figs. 7a–e View Fig ).

Adult Redescription. Length 7.0–26.0 mm, width 2.0–8.0 mm; unicolorous red-brown to black, some species with elytra paler yellow-brown or redbrown, contrasting with pronotum, a few species paler dorsally, with red-brown pronotum and yellow-brown elytra, and unicolorous brown-black ventrally; integument dull or shining, some slightly metallic, a few completely metallic. Body weakly to moderately convex. Setae variable, short and depressed, to long and erect, color variable, gray, yellow, brown, or brown-black, never scale-like or dorso-ventrally compressed.

Head. Color variable, red-brown to black, usually matching pronotum, rarely darker than dorsal surface of pronotum; punctures small and appearing simple, to large and noticeably subumbilicate, nearly contiguous to separated by diameter of one puncture, integument dull to shining; frons weakly to strongly concave anteromedially, without supraorbital groove near eyes; frontal carina usually complete (e. g., Fig. 4b View Fig ), sometimes indistinct medially, broadly curved to V-shaped when viewed from the front, in many nearly confluent with posterior edge of labrum medially, in some weakly projecting; frontoclypeal region without carina, narrow to absent medially; eyes variable in size, ocular index 55–80; antenna weakly serrate ( Fig. 5f View Fig ), serrate ( Figs. 5d, e View Fig ) to strongly serrate ( Fig. 5c View Fig ), antennal insertion proximal to medial edge of eye, separated by narrow unsculptured groove, insertion not visible when viewed from above, antennomere 2 globular to subcylindrical, antennomere 3 subcylindrical to triangular with setation similar to antennomere 2 or similar to antennomere 4, in many intermediate between 2 and 4, antennomeres 4 to 10 usually longer than wide, either uniformly densely setose or with medial line (ml, Fig. 5d View Fig ) bearing less setae than edges, antennomere 11 uniformly oval or with tip constricted as pseudosegment ( Fig. 5d View Fig ), total antennal length variable, not reaching pronotal posterior edge by length of two antennomeres, to extending past pronotal edge by five antennomeres, females with shorter antenna than conspecific males; labrum broadly rounded to truncated anteriorly, not grooved, evenly convex dorsally, with numerous anteriorly directed setae; mandibles bidentate at apex, with dense nearly contiguous punctures laterally; galea and lacinia not reduced, reaching closed mandibles; apical segements of maxillary and labial palps securiform (“hatchet”- shaped); mentum with macrosetae.

Prothorax. Unicolorous in most, a few with pronotal disc paler, commonly with pronotal hind angles and posterior edge paler; pronotum shape variable, wider than long, to longer than wide, sides subparallel to broadly arcuate, often narrowed anteriad, lateral carina complete, sometimes slightly deplanate anteriorly; hind angles subparallel in most, in some divergent, dorsal carina variable, absent to very strongly raised; punctures variable, small, appearing simple, separated by two diameters of a puncture to large, subumbilicate ( Fig. 6c View Fig ) and nearly contiguous, in most with punctures closer laterally than on disc, integument dull to shining; posterior edge with sublateral notches (sln, Figs. 4d, h View Fig ) present in most, a few with incisures absent, posterior-medial antescutellar notch always present, in most medial lobe present, broad, truncate or slightly concave medially (asn, Fig. 4h View Fig ), a few with medial lobe absent; setae directed anteriorly in most; in some, setae directed anteriorly medially, and antero-medially laterally. Hypomeron variably punctured, punctures small, appearing simple, separated by one puncture diameter, to large, subumbilicate and nearly touching, posterior third or fourth in many with impunctate area, most with punctures proximal to pronotosternal suture except at extreme anterior end and near procoxal cavity, a few with punctures separated from suture by impunctate line; posterior margin either emarginate so pronotal hind angle visible in ventral view ( Fig. 33c View Fig ) to sinuate ( Fig. 39c View Fig ) to ear-like, so hind angle not visible in ventral view ( Fig. 19c View Fig ). Prosternal punctation often matching punctation on hypomeron, less dense medially; anterior lobe variable, straight to slightly deflexed, usually short, not extending past dorsal anterior edge, pronotosternal sutures straight, not excavate or grooved anteriorly; prosternal process variable, straight to strongly arcuate, never with lateral expansions extending behind procoxae, procoxal cavity opened posteriorly.

Pterothorax. Mesoventral cavity with lateral edges sinuate, not visible anteriad mesocoxae in lateral view, to expanded ventrally in near 90-degree angle and visible anteriad mesocoxae in lateral view ( Fig. 5g View Fig ), posterior edge of cavity pointed to truncate; mesanepisternum and mesepimeron reaching mesocoxal cavity, mesanepisternum with anterior pit ( Fig. 6a View Fig ). Metaventrite with punctures smaller than on hypomeron, simple to subumbilicate, dense throughout, nearly touching, or less dense medially, separated by 1–2× puncture diameter. Scutellar shield elongate-oval to subtriangular, about twice as long as wide, sides straight or sinuate, dorsal surface flat to strongly convex, sometimes with vague medial carina, anterior margin straight to broadly concave, but never forming semicircular concave indentation, setae radiating from midline, similar in length and shape to setae on pronotum and elytra. Elytra with striae, usually deeply impressed basally, sometimes apically as well, strial punctures connected by groove throughout; interstriae flat to slightly convex with punctures smaller than strial punctures, integument smooth to rough; basal end with carina, carina variable, simple ( Fig. 6d View Fig , arrow) to crenulate ( Fig. 6b View Fig , arrow); apical end broadly rounded; color yellow to black, unicolorous, without maculations, edges in some paler, in most similar in color to pronotum. Legs yellow to black, matching body or contrasting; tarsomeres 1–4 in most bearing apical membranous lobes ventrally ( Figs. 5a, b View Fig ), in some only tarsomeres 1–3 or 2–4 with lobes; lobe on tarsomere 3 largest in most, lobe on tarsomere 2 second largest or subequal to lobe on 3, lobe on tarsomere 1 smaller, sometimes difficult to see and visible only ventrally, or absent, lobe on tarsomere 4 usually smallest, sometimes minute and visible only ventrally, or absent; claws simple, lacking basal setae; metacoxa with ventral plate widest medially and gradually narrowing laterally, narrowest at metanepisternum; metatibia with 2 apical spines or spurs.

Hind Wing. Venation as in Fig. 10a View Fig (after Costa et al. 2010). Wedge cell present. Apical end with single slanting sclerite in apical field.

Abdomen. Punctures simple, similar in size to punctures on metaventrite, almost touching to separated by a puncture diameter, less dense medially; fifth ventrite narrowly to broadly rounded; lateral edge of each ventrite with microserrations ( Fig. 6e View Fig ). Males with tergite IX deeply emarginate posteriorly, sternite IX without medial strut anteriorly, concave membranous patch medially on anterior end. Females with sternite XIII membranous medially, with spiculum ventrale (median strut) about 2× length of sternite XIII plate ( Fig. 8d View Fig ); tergite XIII with V-shaped membranous area anteriorly ( Fig. 8c View Fig ); both sternite XIII and tergite XIII pointed posteriorly. Ovipositor with gonocoxites weakly sclerotized and paraprocts well sclerotized, paraprocts about 5.5× longer than gonocoxites and about two-thirds length of abdomen ( Fig. 8a View Fig ); gonocoxites narrow past opening, with five to eight apico-lateral setae, with subapical styli each bearing a single, long, medial seta ( Fig. 8b View Fig ).

Male Genitalia. Aedeagus with pre-apical lateral expansion present, parameres slightly membranous at extreme apical end, past lateral expansion, apex of paramere with 3–5 setae on dorsal edge, ventral surface with line/patch of 8–12 setae directed anteriorly at pre-apical expansion, line/patch perpendicular to long axis of paramere ( Fig. 9c View Fig ). Median lobe with apex laterally compressed, forming small carina on ventral surface, and apex curved ventrally.

Female Internal Genitalia ( Figs. 7a–e View Fig ). Vagina widened at connection to common oviduct with two lateral, roughly triangular sclerotized patches composed of parallel linear sclerites with minute tubercles in interspaces between linear sclerites. Two membranous, hemisperical colleterial glands present latero-apically at apical end of the vaginal sclerotizations, and slightly latero-apical to connection to common oviduct. Bursa copulatrix elongate-rounded to spherical (figured specimen shrunken), basally lightly sclerotized and ridged, membranous apically, attached to the vagina by a narrow opening, with or without light sclerotization around opening, bursa copulatrix with lateral sclerotized line of minute spines ( Fig. 7b View Fig ) or without sclerotized line ( Fig. 7e View Fig ). One tubular extension present at the apico-ventral end of the bursa copulatrix arising from membranous part. Two blind pedunculate accessory glands arise from bursa copulatrix basal to tubular extension.

Distribution. Species in the genus Hemicrepidius are mainly Holarctic in distribution, being found throughout Europe, Asia, and North America, with species also occurring in the Indomalayan ecozone. In North America, the genus occurs as far south as the Nearctic mountains of northern and central Mexico. The genus, as currently defined, is not known to occur in the Neotropics or Afrotropics.

Larvae. Due to issues with larval associations, in-depth larval descriptions for the genus and some species will be presented in a later work. However, all associated larvae share the following characters: Stemmata absent, prothorax undivided, and inner urogomphal prong of ninth abdominal segment elongate and subparallel, creating a “large” caudal notch.

Biology. Specimens have been collected from May to September, with some long-term traps extending the potential dates into April and October. Based on collecting dates of examined specimens, July appears to be the month of peak activity for adults of the genus. Many specimens representing multiple species were caught at light traps, suggesting that nocturnal flight may be common for Hemicrepidius species. Pupation has been observed to occur during May or early June ( Glen 1950), matching the observed peak activity of collected specimens. Larvae are most often collected in soil, although occasionally specimens have been collected in rotten stumps ( Glen 1950; personal observation). In Europe, stable isotope analysis of gut contents of H. niger showed that species to be predatory and not an herbivore in the larval stage as had been previously reported ( Traugott et al. 2008). It is possible that other species that have been recorded in agricultural fields, such as H. memnonius in North America, are also predatory.

Notes. Members of this genus are quite variable in the shape of the antennomeres, completeness of the frontal carina, and shape of the posterior edge of the hypomeron, all characters often used to define genera, subtribes, and tribes. These characters are useful at the species level, but are too variable to be utilized to define the genus.

The minute lobes on tarsomeres 1 and/or 4 have led to the inaccurate statement that species in Hemicrepidius only have tarsomeres 2 and 3 lobed (e.g., Kishii 1987). It is best to view the lobes in the ventral and lateral positions to accurately determine which are lobed. In most species, tarsomeres 1–4 are lobed, although some species appear to have only 1–3 or 2–4 lobed.

Historically, the lack of a medial frontal carina or the presence of one conjoining the medial margin of the frontoclypeal region near the base of the labrum was stressed to define the genus. This has led some workers to mistakenly assign specimens of the subfamily Elaterinae , tribes Elaterini and Prosternini (Dendrometrinae) to Hemicrepidius , despite these specimens lacking membranous lobes on their tarsi. The character of the frontal carina is quite variable among Hemicrepidius species , but all have the carina very close to the medial edge of the basal margin of the fronto-clypeal region near the base of the labrum, even in species where the frontal carina is slightly projecting.

Japanese authors (e. g., Baba and Ôhira 1956), among the first to recognize the genus in the Palearctic, often recognize as many as six subgenera within Hemicrepidius : Hemicrepidius , Heterathous , Medakathous , Miwacrepidius, Pseudathous , and Yukara . These have all been treated as distinct genera at one time or another. Of these, three deserve more thorough discussion: Medakathous , Miwacrepidius, and Yukara .

Medakathous is returned to synonymy with Hemicrepidius . This decision was made for multiple reasons, despite remarks made by Becker (1979a) that the type species was not congeneric with European Hemicrepidius . First, the genus was originally described as a subgenus of Hemicrepidius . Second, the characters of the fronto-clypeal region used by Kishii (1987) to separate Medakathous from Hemicrepidius are variable within Hemicrepidius , with some New World species sharing the character found in Medakathous . Third, CO1 barcode data support placement of the type species, Hemicrepidius jactatus (Lewis, 1894) , deep within the Hemicrepidius clade with other Eurasian species ( Fig. 3 View Fig , yellow arrow, basal UFBootsupport for Hemicrepidius 100, basal support for Eurasian clade 95). While CO1 fails to resolve deeper relationships (notice basal polytomy in Fig. 3 View Fig ), it appears to be very good at highlighting natural groups, especially when these groups are corroborated by complex morphological characters, in this case by internal female genitalia. Fourth, Ôhira considered Medakathous a subgenus of Hemicrepidius in Oba et al. (2015). While I have only been able to study males of the type species in detail, my examinations support Ôhira’ s placement. I state this synonymy explicitly here, because some workers (e. g., Nakahama et al. 2019) continued to recognize Medakathous after Ôhira proposed the synonymy.

Miwacrepidius is the most widely recognized subgenus. It was the only other subgenus, besides the nominal subgenus, recognized by Cate (2007). It is defined by having a convex scutellar shield bearing a distinct medial ridge. This character, however, is variable within Hemicrepidius , with slight medial ridges present in H. hirtus specimens and H. obscurus specimens (although these are never as pronounced as in the species traditionally placed into Miwacrepidius). Additionally, the CO1 barcode analysis showed these species placed well within a clade of other Eurasian Hemicrepidius species ( Fig. 3 View Fig , purple asterisk). Given the variable character used to define Miwacrepidius, and the lack of support it received from the preliminary DNA analysis, this subgenus is not recognized here, and is considered a synonym of Hemicrepidius .

The third is Yukara , originally synonymized by Becker (1979a), but pulled out of synonymy by Kishii (1987). Examinations of the type species support Becker’ s original synonymization. Hemicrepidius inornatus appears to be part of a species group with the North American species Hemicrepidius pallidipennis ( Mannerheim, 1843) , and the mainland Asian species H. jacobsoni , which was moved to Hemicrepidius from Megathous based on morphological characters. This is also supported by preliminary DNA data with H. inornatus ( Fig. 3 View Fig , green arrow) specimens being recovered next to H. pallidipennis ( Fig. 3 View Fig , basal UFBoot support 97%). Preliminary DNA data do not support any existing subgeneric concept, so they are not applied here.

The only species moved from Megathous with DNA data available is H. dauricus , originally transferred by Becker (1979). DNA data support this move ( Fig. 3 View Fig , black asterisk), with the specimen being recovered in a clade with H. ruficornis and H. simplex ( Fig. 3 View Fig , basal UFBoot support 94%). Morphological examinations of specimens in the NMPC also support this, as H. dauricus shares many characters with H. ruficornis .

Some species of Athous in Southeast Asia may be better placed in Hemicrepidius . These species, in original combinations, are: Athous birmanicus Fleutiaux, 1942 ; Athous ebeninus Fleutiaux, 1918 ; Athous malaisei Fleutiaux, 1942 ; Athous nodieri Fleutiaux, 1918 ; and Athous (Stenagostus) vitalisi Fleutiaux, 1918 . At the time of their descriptions, these five species were compared to other species that were either among those moved to Hemicrepidius by Kishii and Jiang (1996), one of Schwarz’ s Hemicrepidius species , or H. hirtus . Types, however, have not been examined to support such a transfer. Concerns about the placement of these species are mentioned here in order to highlight areas for future study.

Central American species formerly in Hemicrepidius are placed here into the genus Athous Eschscholtz, 1829 . No Central American species has all of the diagnostic features of Hemicrepidius . No species has apico-ventral membranous lobes on its tarsi, although the third tarsomere is expanded ventrally ( Figs. 4e–g View Fig ). None have medial antescutellar notches ( Fig. 4d View Fig ). Most importantly, the internal female genitalia ( Figs. 8e–g View Fig ) are very different from those of Hemicrepidius ( Figs. 7a–e View Fig ). However, they are nearly identical to the internal female genitalia of Athous vittatus , the type species of Athous ( Leseigneur 1972; personal examination), which supports the movement of these species to Athous . Having a ventrally expanded third tarsomere is similar to what is seen in many Athous species , such as Athous subfuscus (Müller, 1764) . In his examinination of the fauna of France, Leseigneur (1972: 193) stated that A. subfuscus had similar internal female genitalia to A. vittatus as well. The ML tree ( Fig. 2 View Figs , blue arrows) was the only DNA analysis to group the Central American species with Athous (basal support 81%), but all three analyses support the removal of these species from Hemicrepidius ( Figs. 1–3 View Figs View Fig ). Although the DNA data are unclear about the precise placement, the internal female genitalic characters provide strong support for this transfer. This generic transfer once again returns the genus Athous to the Central American fauna below Mexico.

Asaphes longipennis Candèze, 1863 , described from Venezuela and Colombia, is moved to the genus Pomachilius Candèze, 1860 . All characters of the type specimen support this placement, such as the ventrally expanded third tarsomere and head with ventrally directed mouthparts and a complete frontal margin, features that are often found in species of Elaterinae . With the only other species formerly in Hemicrepidius in South America currently in the genus Sharon , Hemicrepidius is removed from the fauna of South America.

Species in Hemicrepidius could be confused with other genera with tarsomeres bearing membranous lobes. Species in Elaterinae genera with lobed tarsi, such as Crepidius Candèze, 1859 and Dipropus Germar, 1839 , may be mistaken for Hemicrepidius at a quick glance. These genera can easily be distinguished from Hemicrepidius by the wide impunctate area on the hypomeron along the pronotosternal suture, which is often grooved anteriorly (e. g., Fig. 4c View Fig , il), the deep frontoclypeal region with the frontal carina well separated from the posterior margin of the labrum (compare Fig. 4a View Fig with Fig. 4b View Fig ), and the internal female genitalia being different than that found in Hemicrepidius .

The most easily confused genus is Athous . In the Nearctic, all Athous species can be distinguished from Hemicrepidius by the lack of the medial antescutellar notch (compare Fig. 4d View Fig with Fig. 4h View Fig ), as defined by Becker (1979a). In the Palearctic realm, this situation becomes more complex. Species such as Athous subfuscus possess a medial antescutellar notch, but in addition to differences in internal female genitalia (similar to Figs. 8e–g View Fig ), others can be distinguished from Hemicrepidius by having the lobe on tarsomere 4 subequal to the lobe on tarsomere 3. The majority of Eurasian Athous , however, will not have a medial antescutellar notch.

Other genera in Eurasia, such as Stenagostus and Megathous (in the restricted sense used here), share many external characteristics with Hemicrepidius , and until they are revised can only be distinguished using genitalic characters, specifically males of both genera lacking pre-apical lobes on parameres (e. g., Fig. 10b View Fig ) and female internal genitalia dissimilar to those illustrated in Figs. 7a–e. View Fig

LIST OF SPECIES INCLUDED IN THE GENUS

No attempt has been made to place these species into species groups. The names and synonymies of Palearctic species follow Cate (2007). Synonyms and original combinations for North American species are given in their species descriptions below.

Eurasian species – 58 species and subspecies Hemicrepidius agajewi Platia, 2008 Hemicrepidius amami Kishii, 1985 , restored combination

Hemicrepidius yamawakii Ôhira, 1987 Hemicrepidius carbonarius (Stepanov, 1935) (Harminius)

Hemicrepidius chinensis Kishii and Jiang, 1996 Hemicrepidius colichicus (Iablokoff-Khnzorian, 1962) (Athous)

Hemicrepidius consors (Heyden, 1884) (Athous) Hemicrepidius coreanus Kishii, 2002 Hemicrepidius corvinus ( Reitter, 1905) (Athous) Hemicrepidius cotesi (Candèze, 1895) (Athous) Hemicrepidius cylindricus Kishii and Jiang, 1996 Hemicrepidius dauricus (Mannerheim, 1852) (Athous) , restored combination

Athous eximius Buysson, 1904

Athous urgensis Schwarz, 1900 Hemicrepidius decorus (Fleutiaux, 1918) (Athous)

Hemicrepidius desertor amacicola Kishii, 1969 Hemicrepidius desertor chejuanus Kishii, 2002 Hemicrepidius desertor desertor (Candèze, 1873) (Psephus)

Athous virens Candèze, 1873

Athous sanguinicollis J. Frivaldszky, 1892 Athous brunneipennis Lewis, 1894

Corymbites isshikii Miwa, 1928

Athous flavipennis Miwa, 1934

Hemicrepidius shirozui Kishii, 1958 Hemicrepidius desertor taishu Kishii, 2001 Hemicrepidius desertor yakuensis Kishii, 1969 Hemicrepidius rufoabdominalis Nakane and Kishii, 1958