Ochodaeus montanus, Fuente Hind, 1912

Gutierrez, Jean-Bernard Huchet José Luis Lencina, 2024, New insights and comparative morphology of the rare Western Palearctic species Ochodaeus montanus Fuente, 1912 and its closest relative, O. inermis Reitter, 1893 (Coleoptera: Scarabaeoidea: Ochodaeidae), Insecta Mundi 2024 (79), pp. 1-16 : 11-14

Distinguishing O. montanus from O. inermis : new comparative discriminating characters

Ochodaeus montanus can be distinguished from O. inermis by a series of morphological characters. The most distinctive feature is the presence of a prominent tooth on the distal part of the posterior margin of the hind femora in both sexes of O. montanus ( Fig. 5 ), which is always absent in both sexes of O. inermis . In O. montanus , the clypeus is consistently convex, forming a curve that reaches the upper edge of the eye on either side ( Fig. 1, 2 , 28 ). In contrast, the clypeus of O. inermis is weakly sinuate on either side of the middle and typically slightly flattened anteriorly ( Fig. 11, 12 , 29 ). The pronotal punctation also exhibits notable differences between the two species: O. montanus shows a simple, very dense, and strong punctation composed of tightly packed setose squamiform granules ( Fig. 1, 2 , 23 ), whereas the punctation in O. inermis is double and more superficial, comprising both tight setose squamiform granules and distinct scattered umbilicated punctures (this distinction is most apparent under low-angle lighting, with the use of a calque layer) ( Fig. 11, 12 , 24 ). In O. montanus , the strial punctures on elytra are very large, resulting in narrow intervals whose width is roughly equal to 2 or 3× the diameter of the punctures constituting the striae ( Fig. 25 ). Conversely, in O. inermis , the striae consist of medium-sized punctures with interval widths approximately 4 to 5× the diameter of the strial punctures ( Fig. 26 ). In ventral view, the abdomen of O. montanus exhibits large setiferous granules along the anterior edge of the sternites, with these granules being spaced approximately 2–3× their diameter, particularly on ventrites IV-VI ( Fig. 6 ). In contrast, O. inermis has more reduced granules that are closer together, separated by about 1–2× their diameter ( Fig. 9 ). Additionally, in tergal view, the shape of the stridulatory peg (plectrum) located on sternite VI of the abdomen proves to be a discriminating character in differentiating the two species ( Fig. 8, 10 ).

Color patterns: within the Ochodaeini tribe, which includes, among others, the genera Ochodaeus Dejean, 1821 and Parochodaeus Nikolajev, 1995 , the coloration of the habitus is relatively variable within a single species and thus not highly discriminatory. However, O. inermis is typically yellowish-tan to light brown, sometimes darkened, whereas the four known specimens of O. montanus exhibit a dark reddish-brown coloration.

Male genitalia

Ochodaeus montanus : The phallobase is elongated and dorsally curved, tapering to a point at the apex. The parameres are short, symmetrical, and rounded apically. The internal sac contains a single, large, boomerang-shaped endophallite ( Fig. 16 ). The genital segment (urite IX) is elongated, with the base being nearly straight ( Fig. 17 ).

Ochodaeus inermis : The phallobase resembles that of the previous species. The parameres are short, symmetrical, and only slightly pointed at the apex. The internal sac contains two endophallites: one medium-sized, arched, and serrated along its convex surface, and another smaller one located beside it. The surface of the internal sac is partially covered with raspulae and fine spicules ( Fig. 18 ). The genital segment (urite IX) is relatively wide and transverse, with the base distinctly sinuate in the middle ( Fig. 19 ).

Female terminalia

Ochodaeus montanus ( Fig. 20 ): The segment is complete. Tergite IX is arch-shaped, narrow, poorly sclerotized dorsally, and glabrous. Gonopod IX is trimeric, consisting of the subcoxite, coxite, and stylus. The subcoxite is roughly triangular and concave, with four to five long setae aligned at the tip of the ventral edge. The coxite is elongated, roughly cylindrical, slightly flattened at the apex, and bears 10 long setae. The style is elongated, digitiform, and bears eight thin setae apically. The trimeric gonopod IX was shown by Huchet (2021) to be a character of Ochodaeini , in contrast to the same structure in Nothochodaeini Nikolajev, 2015 ( Nothochodaeus Nikolajev, 2005 and Ceratochodaeus Huchet, 2017 ) that is dimeric and lacks a terminal stylus.

Ochodaeus inermis ( Fig. 22 ): The gonopod IX is trimeric. The subcoxite is roughly triangular and concave, with five to six long setae arranged in staggered rows at the tip of the ventral edge. The coxite is elongated, roughly cylindrical, and slightly flattened at the apex, bearing 11 long setae. The style is short, digitiform, and bears five thin setae apically.

Sexual dimorphism

In O. inermis , the anterior tibiae of males are significantly narrower with sharper teeth, whereas in females, the tibiae are enlarged, and the teeth are wider ( Fig. 14 ). To our knowledge, these characteristics associated with sexual dimorphism encountered across multiple species within the genus Ochodaeus have not been documented in the literature. Additionally, the clypeus in males is typically more markedly sinuate on either side of the midline, whereas in females, the clypeus exhibits a more smoothly curved anterior margin.

In O. montanus , we note the presence of a small tooth located on the anterior margin of male profemora. Although this character was mentioned in Baguena Corella’s (1967) diagnosis of this species and later included by Baraud (1992) in his identification key, neither of these authors had seen specimens of O. montanus . As pointed out by López-Colón (1986: 34), Baguena Corella made a number of errors, mentioning O. montanus as follows [translated from Spanish]: “ It differs from the preceding one by its anterior femora provided with a small tooth ...”, “ this obviously refers to the posterior femora, as indicated in the species key on the same page (page 212), an error that went unnoticed and, although evident, should be clarified to avoid confusion ”.

Key to genera and species of Ochodaeidae of the Iberian Peninsula

1. Apex of elytra dentate, interlocking with 2 tubercles on tergite VII (propygidium) margin ( Fig 33 ). Anterior tibiae tridentate on outer margin, teeth equidistant, basal tooth well developed ( Fig. 31 ). First metatarsomere strongly dilated in males. Size: 4–8 mm. Parochodaeus pocadioides (Motschulsky)

— Elytral apex and tergite VII without coaptation mechanism. Anterior tibiae tridentate on outer margin, basal tooth very small, located in proximal third ( Fig. 32 ). Male first metatarsomere not dilated......................................................................... ( Ochodaeus ) 2

2. Anterior margin of clypeus distinctly incised in the middle ( Fig. 30 ). Size: 4.0–6.5 mm.......................................................................... O. chrysomeloides (Schrank)

— Anterior margin of clypeus not incised....................................................... 3

3. Metafemur with a distinct acute tooth at the distal part of the posterior margin in both sex ( Fig. 4, 5 ). Profemur with a small tooth along the anterior margin in male. Anterior margin of the clypeus regularly convex ( Fig. 28 ). Elytral intervals slightly convex, their width about 2–3 × the diameter of the strial punctures ( Fig. 25 ). Size: 4.8–5.7 mm............................. O. montanus Fuente

— Metafemur unarmed, or at most with a blunt lamina at the distal part of the posterior margin in both sex ( Fig. 15 ). Profemur lacking a small tooth along the anterior margin in male. Anterior margin of the clypeus hardly flattened in front and slightly sinuate on each side of the middle ( Fig. 29 ). Elytral intervals width about 4–5 × the diameter of the strial punctures ( Fig. 26 ). Size: 4.0–5.7 mm............................................................................. O. inermis Reitter

Clave de los géneros y especies de los Ochodaeidae de la Península Ibérica

1. Ápice de los élitros dentado, entrelazado con dos tubérculos en el margen del VII tergito (propigidio) ( Fig 33 ). Tibias anteriores tridentadas en el margen externo, dientes equidistantes, diente basal bien desarrollado ( Fig. 31 ). Primer metatarsómero fuertemente dilatado en los machos. Tamaño: 4–8 mm ............................................ Parochodaeus pocadioides (Motschulsky)

— Ápice elitral y VII tergito sin mecanismo de coaptación. Tibias anteriores tridentadas en el margen externo, diente basal muy pequeño, situado en el tercio proximal ( Fig. 32 ). Machos con el primer metatarsómero no dilatado................................................. ( Ochodaeus ) 2

2. Margen anterior del clípeo claramente inciso en el centro ( Fig. 30 ). Tamaño: 4.0–6.5 mm........................................................................ O. chrysomeloides (Schrank)

— Margen anterior del clípeo no inciso........................................................ 3

3. Metafémures con un diente afilado distinto en la parte distal del margen posterior en ambos sexos ( Fig. 4, 5 ). Profémures con un pequeño diente a lo largo del margen anterior en el macho. Margen anterior del clípeo regularmente convexo ( Fig. 28 ). Intervalos élitrales ligeramente convexos, de una anchura de 2–3 veces el diámetro de los puntos estriales ( Fig. 25 ). Tamaño: 4.8–5.7 mm............................................................................ O. montanus Fuente

— Metafémures inermes, o a lo sumo con una lámina roma en la parte distal del margen posterior en ambos sexos ( Fig. 15 ). Profémur carente de un pequeño diente a lo largo del margen anterior en el macho. Margen anterior del clípeo apenas aplanado en el frente y ligeramente sinuado a cada lado de la parte media ( Fig. 29 ). Anchura de los intervalos elitrales aproximadamente 4–5 veces el diámetro de los puntos estriales ( Fig. 26 ). Tamaño: 4.0–5.7 mm............................ O. inermis Reitter

Figures

Figures 4–5. Ochodaeus montanus, diagnostic characters. 4) Apical view, inset illustrating the large punctures of the elytal striae, the arrows showing the characteristic tooth at the distal part of the posterior margin of the metafemur in both sexes. 5) Posterior leg in ventral view (Photos J.-B. Huchet).

Figures 1–2. Ochodaeus montanus habitus, dorsal view. 1) Male. 2) Female (Photos J.-B. Huchet).

Figures 27–30. Spanish species of Ochodaeidae, head outline. 27) P. pocadioides (Motschulsky). 28) O. montanus Fuente.29) O. inermis Reitter. 30) O. chrysomeloides (Schrank) (schematic drawings J.-B. Huchet).

Figures 11–12. Ochodaeus inermis habitus, dorsal view. 11) Male. 12) Female (Photos J.-B. Huchet).

Figures 23–26. Comparison of pronotal and elytral punctation between Ochodaeus montanus and O. inermis. 23) O. montanus, close-up of the pronotum. 24) O. inermis, close-up of the pronotum, showing clearly visible umbilicated punctures. 25) O. montanus, elytral striation, illustrating large-sized punctures and narrow intervals. 26) O. inermis, elytral striation, showing medium-sized punctures and wide intervals (Photos by J.-B. Huchet).

Figures 6–10.Morphological comparison between Ochodaeus montanus and O. inermis. 6) O. montanus, abdomen in ventral view showing the large setiferous granules along the anterior edge of the sternites. 7) O. montanus, abdomen, tergal view. 8) O. montanus, abdominal stidulatory peg (plectrum), inset illustrating a schematic outline of the plectrum. 9) O. inermis, abdomen in ventral view. 10) O. inermis, abdominal stidulatory peg (plectrum), inset illustrating a schematic outline of the plectrum. (Photos J.-B. Huchet).

Figures 16–17. Ochodaeus montanus, male genitalia. 16) Aedeagus in lateral views, with the endophallus not everted, inset illustrating the large single endophallite. 17) Genital segment (urite IX) in dorsal view (Ep: endophallite; Lht9: Laterohemitergite 9; Sg: spiculum gastrale; Vs: ventral synsclerite) (Photos J.-B. Huchet).

Figures 18–19. Ochodaeus inermis, male genitalia. 18) Aedeagus in lateral views, with the endophallus not everted, inset illustrating the two endophallites (EP1, EP2). 19) Genital segment (urite IX) in dorsal view (Photos J.-B. Huchet).

Figures 20–22. Female terminalia. 20) Ochodaeus montanus, NEOTYPUS, female gonopod IX. 21) Ditto, O. chrysomeloides. 22) O. inermis, external genitalia (Cx: coxite; Ep: epipleurite; Ht: hemitergite; Pi: posterior intestine; Sc: subcoxite; St: style) (Fig. 20: photo M. Paris (MNCN) and J.-B. Huchet; Fig. 21,22: photos J.-B. Huchet).

Figures 13–15. Ochodaeus inermis. 13) Female, habitus, latero-dorsal view. 14) Protibia, sexual dimorphism. 15) Posterior leg in ventral view, a blunt lamina visible at the distal part of the posterior margin (Photos J.-B. Huchet).

Figures 31–33. Parochodaeus and Ochodaeus, diagnostic characters. 31) Parochodaeus pocadioides, right protibia, dorsal view. 32) Ochodaeus chrysomeloides, right protibia, dorsal view. 33) Parochodaeus Nikolajev, 1995, dentate elytral apices and tergite VII interlocking mechanism, characteristic of the genus (Fig. 31, 32: J.-B. Huchet; Fig. 33: photo © M. Paulsen).