Pristilophus, Latreille, 1834

Etzler, Frank E., 2024, Generic Changes for Some Nearctic Prosternini (Coleoptera: Elateridae: Dendrometrinae: Neopristilophus Buysson, 1894 and Pristilophus Latreille, 1834) to Align with Palearctic Concepts, The Coleopterists Bulletin 78 (2), pp. 125-140 : 132-138

PRISTILOpHUS Latreille, 1834

Pristilophus Latreille 1834: 151 ; Schimmel et al. 2015: 14, 36. Type species: Elater melancholicus Fabricius, 1798 , designated by Erichson (1843).

[As subgenus of Selatosomus Stephens, 1830 ]: Kishii 1966: 54; Dolin 1982: 228; Gurjeva 1985: 571; Gurjeva 1989: 226; Tarnawski 1995: 5; Tarnawski 1996: 632; Tarnawski 2001: 294.

[As a synonym of another genus]: Schenkling 1927; Platia 1994.

Tesolasomus Johnson in Mathison 2021: 346. Type species: Elater semivittatus Say, 1823 , by original designation. New synonym.

North American Species

Pristilophus blanditus ( Brown, 1936) ( Ludius ), new combination

Pristilophus castanicolor (Fall, 1934) ( Ludius ), new combination

Pristilophus deceptor ( Brown, 1936) ( Ludius ), new combination

Pristilophus edwardsi (Horn, 1871) ( Corymbites )

Pristilophus festivus (LeConte, 1857) ( Corymbites )

Pristilophus funereus ( Brown, 1936) ( Ludius ), new combination

Pristilophus lanei (Becker, 1949) ( Ctenicera ), new combination

Pristilophus morulus (LeConte, 1863) ( Corymbites )

Pristilophus pulcher ( LeConte, 1853) ( Corymbites )

Pristilophus semivittatus (Say, 1823) ( Elater )

Pristilophus sexguttatus ( Brown, 1936) ( Ludius ), new combination

Pristilophus sexualis (Brown, 1935) ( Ludius )

Pristilophus suckleyi olympiae ( Van Dyke, 1932) ( Ludius )

Pristilophus suckleyi suckleyi (LeConte, 1857) ( Corymbites )

Pristilophus trivittatus ( LeConte, 1853) ( Corymbites ), new combination

KEY TO NORTH AMERICAN SPECIES OF PRISTILOPHUS , MALES ONLY (adapted from Brown 1935a, 1936, Tarnawski 1995, and Mathison 2021)

1. Fifth abdominal ventrite modified, swollen or with a ribbed fold covered in dense ves- titure ( Fig. 4D , Group II) ........................ 2

1′. Fifth abdominal ventrite not modified, with or without fringe of dense setae ( Figs. 4B, C )...................................................... 3

2(1). Length 11 to 16 mm; black or bicolored ( Fig. 3D )................ P. morulus (LeConte)

2′. Length 7 to 8 mm; brown or red-brown .... ................................... P. sexualis (Brown)

3(1). Fifth abdominal ventrite with fringe of dense setae ( Fig. 4C , Group III).............. 4

3′. Fifth abdominal ventrite without fringe of dense setae ( Fig. 4B , Group I) .............. 10

4(3). Elytra bicolored, black or brown and yellow...................................................... 5

4′. Elytra black or brown, immaculate......... 9

5(4). Antenna just attaining the apex of the posterior pronotal angle, flagellar antennomeres not longer than wide .......................... .................................. P. semivittatus (Say)

5′. Antenna extending beyond the apex of the posterior pronotal angle, flagellar antennomeres variable, longer than wide in most ... 6

6(5). Pronotum variable, most black with a broad sublateral vitta on each side pale red (similar to Fig. 3E ), some entirely black; east of Rocky Mountains......................... 7

6′. Pronotum entirely black; Rocky Mountains and west.......................................... 8

7(6). Pronotum strongly convex; flagellar antennomeres nearly as long as wide................. ....................................... P. lanei (Becker)

7′. Pronotum less strongly convex; flagellar antennomeres longer than broad................. .............................. P. trivittatus (LeConte)

8(6). Third antennomere equal in length to fourth ...................... P. blanditus (Brown)

8′. Third antennomere shorter than fourth ..... ............................. P. sexguttatus (Brown)

9(4). Antenna surpassing posterior pronotal angle by a distance equal to length of two and one-half antennomeres .............................. .................................. P. deceptor (Brown)

9′. Antenna just attaining apex of posterior pronotal angle ( Fig. 3C ) ............................ ................................. P. funereus (Brown)

10(3). Anterior margin of scutellar shield arcuate in dorsal view ( Fig. 5C ); ninth elytral interval with supplemental stria at apical third ( Fig. 5D ) ........................................11

10′. Anterior margin of scutellar shield with medial tubercle in dorsal view ( Fig. 5B ); ninth elytral interval without supplemental stria........................................................ 13

11(10). Posterior half of pronotum very finely and sparsely punctate ................................... 12

11′. Posterior half of pronotum moderately coarsely and closely punctate.................... .................................... P. edwardsi (Horn)

12(11). Each elytron bimaculate with yellow ( Fig. 5A ) .......... P. SUckLEyI SUckLEyI (LeConte)

12′. Each elytron immaculate........................... ............. P. SUckLEyI OLympIaE (Van Dyke)

13(10). Body unicolorous, red-brown ( Fig. 3A ) ................................ P. castanicolor (Fall)

13′. Body bicolored, pronotum with red lateral maculae and elytra yellow with black or dark brown maculae.............................. 14

14(13). Pronotum with punctures separated by distance equal to own diameter at sides and about twice own diameters in middle; transverse black band of elytron never extended from lateral margin to apex, apex never dark except on sutural interval ........ ................................ P. pulcher (LeConte)

14′. Pronotum with punctures separated by distance less than own diameter at sides and about own diameter in middle; elytral markings variable, in many transverse band extended on margin to apex and elytral apex brown or black, in some markings reduced with transverse band reduced to spots or absent so apex of elytra also pale ( Fig. 3B )................. P. festivus (LeConte)

Diagnosis. Pristilophus will most often be confused with Selatosomus . Males can readily be distinguished from Selatosomus by the presence of either a modified and ridged last ventrite or a setal fringe for most. In males lacking these features or for females, they can be distinguished by an anterior tubercle on the scutellar shield ( Fig. 5B ) or a supplemental elytral stria ( Fig. 5D ). The male aedeagus will also have flattened parameres and a median lobe that narrows at the apex and is often subequal to or shorter than the length of the parameres. Larvae can be distinguished from those of Selatosomus by the presence of a tridentate nasale.

Genus Redescription . Length 7 to 17 mm. Integument color variable, unicolorous brown to black or elytra paler, elytra with or without markings, pronotum unicolorous or with red bands on lateral edge of various widths, in some, head integument also bicolored; legs variable, similar in color to rest of body or paler. Head: Mouthparts prognathous, mandible bluntly bidentate; labrum sclerotized, semicircular; supra-antennal carina directed medially toward posterior edge of labrum, incomplete medially; frons flat to impressed antero-medially; punctures simple to subumbilicate, larger punctures denser; antenna with sensory elements beginning on antennomere 4, antennomere 3 subcylindrical, length variable, antennomere 4–10 shape variable, subtriangular to rectangular, as wide as long to 2× longer than wide, antennomere 11 oval, apex with slight constriction at most, antennal length variable, reaching to surpassing posterior pronotal hind angles. Pronotum: Wider than long, medial impression absent or on postero-medial third only; setae variable in length, direction variable with anterior half uniformly directed posteriorly, posterior half with mixed directions (e.g., Fig. 3C ), short setae with orientation obscured, punctures simple to subumbilicate, density variable, lateral punctures similar in size to punctures on head, medial puncture size variable, smaller or equal in size to lateral punctures; pronotal hind angle unicarinate; sublateral plicae present. Hypomeron with dense, simple to subumbilicate punctures on anterior four-fifths; posterior edge with hind angle visible ventro-laterally, angulate in middle, blunt tubercle behind procoxae; medial hypomeral bead present, lateral edge of bead poorly defined in most. Prosternum with pronotosternal sutures straight; anterior lobe broadly rounded, on same plane as rest of pronotum to slightly deflexed (not more than 30 degrees); prosternal process straight to slightly directed dorsad (not more than 30 degrees from plane of prosternum) posteriad of procoxae, with medial area raised forming blunt tubercle before apex. Pterothorax: Mesocoxal cavity open to mesanepisternum and mesepimeron, mesosternal fossa with sides gradually sloping. Scutellar shield subquadrate, anterior margin broadly rounded or with medial tubercle ( Fig. 5B ), posterior margin broadly rounded. Elytra with striae punctate and impressed, some with supplemental stria on the ninth interstria ( Fig. 5D ). Abdomen: Apex of last ventrite variable, in some modified in males, with setose subapical ridge or fold ( Fig. 4D ), some with fringe of elongate setae at apex ( Fig. 4C ), or unmodified ( Fig. 4B ); apex of female with aspects of previous reduced. Aedeagus ( Figs. 4F–H ): Paramere shape variable, flattened dorso-ventrally or widening apically along medial edge, apex of paramere membranous, with or without setae, with subapical lateral expansions; median lobe constricted apically, in most length subequal to or shorter than length of parameres; phallobase variable in length, one-fourth to one-third of total length. Ovipositor and internal female genitalia not examined.

Comments. Pristilophus was often considered a subgenus of Selatosomus (e.g., Tarnawski 1995). However, it was raised to the generic level by Schimmel et al. (2015).

Johnson originally suggested Tesolasomus as a manuscript name in his 1992 dissertation, and the name was finally published in 2021 ( Mathison 2021). In Johnson (1992: 122–123, couplet 3), he separated Tesolasomus from Selatosomus by the following adult characters: Tesolasomus having the pronotal disc and metaventrite with coarse to um- bilicate punctures, elytral striae with large and shallow punctures, and tarsomere 4 long, 0.8–0.9× length of tarsomere 1; versus Selatosomus having the pronotal disc and metaventrite with fine to moderately sized punctures, elytral striae with moderately sized punctures, and tarsomere 4 short, <0.5× length of tarsomere 1. These characters are highly subjective, reducing their utility in defining groups [compare Figs. 3C and D to Figs. 3E and F ; note: Figs. 3A, B considered part of Selatosomus by Johnson (1992; also in Mathison 2021)]. The character of the pronotal punctures has different interpretations possible which overlap with one another. The elytral strial character may be good but would not work with the species placements in Johnson (1992). For example, P. festivus ( Fig. 3B ) has the elytral striae with large and shallow punctures that Johnson (1992) used to define Tesolasomus but was placed by Johnson (1992) into Selatosomus . The tarsomere character would be better written as tarsomere 1 long or short, as the length of tarsomere 4 appears similar between the two genera. However, the character may not be applicable for all species included in each genus, with some species falling in the middle with tarsomere 4 around 0.5× length of the tarsomere 1. Johnson (1992) is discussed in detail here since it is the only work that justifies and gives characters to distinguish genera, even though it is unpublished (see Douglas and Laplante 2022). In summary, Johnson (1992) did not provide ade- quate characters to define his generic concepts and to justify how species are placed in each genus he recognized.

Part of the issue of which genus to recognize is the confusion surrounding the author of Pristilophus as discussed above. Confusion concerning type species also arises in Johnson’s (1992) dissertation. In the remarks for Selatosomus, Johnson (1992: 135) stated that Elater cruciatus Linnaeus, 1758 was designated as the type of both Pristilophus Germar and Selatosomus by Hyslop (1921) and the former was treated as a subgenus of the latter, an impossible situation with shared type species. While Hyslop did state that the type of Selatosomus is E. cruciatus by elimination, he correctly indicated that the author of Pristilophus was Latreille and identified the correct type species, E. melancholicus , and listed it as a distinct genus. Méquignon (1930) corrected Hyslop and stated that Elater aeneus Linnaeus, 1758 was the type of Selatosomus . While this was noted by Johnson (1992), he did not list Pristilophus as a valid genus or a synonym of another genus in his dissertation. Because Johnson (1992) considered the same wrong species as the type of Selatosomus and Pristilophus , he treated them as synonyms. This error led him to erect Tesolasomus .

There are, however, many characters that serve to synonymize Tesolasomus with Pristilophus . First, Tarnawski (1995) looked at eight North American species in his revision of Selatosomus and placed these species into Pristilophus (then treated as a subgenus of Selatosomus ). Tarnawski was also the most recent author to compare specimens between regions in a publication. Two of them, P. morulus and P. sexualis , were placed into the same species group as the type species P. melancholicus , all of which share the modified fifth abdominal ventrite in males ( Fig. 4D ). This similarity of the type species is the strongest piece of evidence for synonymy (see also Douglas and Laplante 2022). Larval characters also unite these species. Glen (1950) looked at four species, P. spretus [= P. punctatissimus (Ménétriés) ], P. festivus , P. sexualis , and P. semivittatus , in detail. The first three species were put together in a species group by Glen (1950), and the lone specimen of P. semivittatus was put into a separate group very close to the other three. Dolin (1978, 1982) also looked at larvae, and covered three relevant species, P. melancholicus , P. spretus (= P. punctatissimus ), and P. cruciatus , which all formed a group in Dolin’s work. Both Glen (1950) and Dolin (1978, 1982) noted that these species had a tridentate nasale. This is another point of evidence that unites the different species groups and unites the North American and Palearctic faunas.

Authors have often split Pristilophus into many subgroups, which serve as other lines of evidence to synonymize Tesolasomus with Pristilophus . Tarnawski (1995) split Pristilophus into three groups based on the fifth abdominal ventrite. Group I had an unmodified fifth abdominal ventrite ( Fig. 4B ), Group II had a ridged and modified fifth abdominal ventrite ( Fig. 4D ), and Group III had a dense setal fringe at the apex of the fifth abdominal ventrite ( Fig. 4C ). This grouping is followed here. Brown (1935a, 1936) also placed the species into three groups, although different from Tarnawski’s groups which are listed in parentheses following Brown’s groupings to compare. These were the cruciatus -species group, for P. cruciatus and allies (Group I), the edwardsi -species group, for species with a supplemental stria on the apex of the ninth interstria ( Fig. 5D ; Groups I and II), and the semivittatus -species group, mostly for species with a dense setal fringe at the apex of the fifth ventrite (Group III, with some Group I). The groups of Tarnawski (1995) followed here are likely artificial. For example, P. semivittatus (Group III) has the scutellar shield with an apical tubercle ( Fig. 5B ), similar to P. festivus and P. castanicolor (both Group I).

Pristilophus will most easily be confused with the genus Selatosomus . The majority of species of Pristilophus will have males with either a modified terminal abdominal segment or an apical setal fringe on the last ventrite ( Figs. 4C, D ) that will readily distinguish them from species of Selatosomus . Species of Pristilophus with unmodified terminal abdominal segments ( Fig. 4B ) cannot be distinguished from species of Selatosomus ( Fig. 4A ) using this character. This lack of a modified terminal abdominal segment led Johnson (1992; also in Mathison 2021) to consider these species as part of Selatosomus . However, multiple characters place these species (couplets 11 to 14 in key above) in Pristilophus over Selatosomus , utilizing distinguishing characters discussed below. Species of Pristilophus have male genitalia with broad, flattened parameres and a narrow apex of the median lobe, with the median lobe in the majority of species equal in length to or shorter than the length of the parameres ( Figs. 4F–H ), while species of Selatosomus have rounded parameres and a broad median lobe that is always longer than the parameres ( Fig. 4E ; also Fig. 3E ). Some species of Pristilophus have elytra with maculae (e.g., Figs. 3B , 5A ), while species in Selatosomus always have immaculate elytra ( Figs. 3E, F ). Species of Pristilophus with immaculate elytra that could be confused with Selatosomus will have either a scutellar shield with an apical tubercle ( Fig. 5B , compare to Fig. 5C ), or have a supplemental stria at the apex of the ninth elytral interval ( Fig. 5D , compare to Fig. 5E ). Larvae of Pristilophus also have a tridentate nasale, while larvae of Selatosomus have a unidentate nasale ( Dolin 1978; Glen 1950; Johnson 1992). It should also be noted that the characters used to distinguish Pristilophus from Selatosomus in the key to genera in Schimmel et al. (2015) only apply to the type species and not for all species in Pristilophus . The characters presented here better capture the diversity and should work on the global level to distinguish the two genera.

Figures

Fig. 4. Characters distinguishing Selatosomus and Pristilophus. Last abdominal ventrite:A) S. semimetallicus, B) P. festivus, C) P.funereus, D) P. morulus. Male aedeagus, dorsal view: E) S. aeripennis, after Brown (1935b), F) P. festivus, after Brown (1935a), G) P. funereus, after Brown (1936), H) P. morulus, after Brown (1935a).

Fig. 3. Dorsal habitus of Pristilophus and Selatosomus species. A) P. castanicolor, Wyoming, USA, B) P. festivus, Montana, USA, C) P. funereus, Montana, USA, D) P. morulus, Montana, USA, E) S. lateralis, California, USA, F) S. semimetallicus, Montana, USA. Not to scale.

Fig. 5. Characters distinguishing Selatosomus and Pristilophus. P. suckleyi suckleyi, Washington, USA: A) Dorsal habitus, D) Elytra, dorsal view, showing supplemental stria (white arrow) on ninth interval, with intervals labeled. P. festivus: B) Scutellar shield, dorsal view. S. semimetallicus: C) Scutellar shield, dorsal view, E) Elytra, dorsal view, with intervals labeled. Not to scale.