Hybovalgus Kolbe, 1904

Ricchiardi, Enrico, 2017, Revision of Chinese mainland Hybovalgus Kolbe, 1904, with description of a new species, and Excisivalgus Endrödi, 1952 reduced to synonymy with Hybovalgus (Coleoptera: Scarabaeidae), European Journal of Taxonomy 340 (340), pp. 1-32 : 5-11

Hybovalgus Kolbe, 1904

Hybovalgus Kolbe, 1904: 55 .

Excisivalgus Endrödi, 1952: 62 , syn. nov.

Type species

Hybovalgus bioculatus Kolbe, 1904 by monotypy.

Diagnosis

In the years after 1904 some entomologists tried to better define Hybovalgus ( Arrow 1944; Paulian 1961; Krikken 1978; Miyake 1985), but could not find even one morphological synapomorphy. Krikken (1984) and Miyake (1985) wrote that the shape of the parameters was peculiar to Hybovalgus . Miyake (1985) distinguished Hybovalgus from Dasyvalgus as follows: “Parameres more or less prolonged, not confluent each other, with a excision on each inner edge, Hybovalgus . Parameres vestigial, sometimes confluent each other, Dasyvalgus ”. The paramere shape of each genus is different, and easily distinguishable, although the meaning given to the word “vestigial” by Miyake is not clear.

After studying many specimens (including all the species of Hybovalgus in Taiwan), we conclude that the males of Hybovalgus can be distinguished from those of Dasyvalgus by a series of non-exclusive characters and by the shape of the parameres ( Fig. 3 A–F). The special shape of Hybovalgus parameres is distinctive compared with the variable parameres of males of Dasyvalgus species. This paramere shape, that we define as “ Hybovalgus shape”, within the Chinese Valgina is shared only with Dasyvalgoides denticulatus Endrödi, 1952 , in a monotypic genus. The relationship between these two genera must still be investigated, but the latter species is readily distinguishable from any Hybovalgus by the protibia with six teeth; and from H. sexdentatus by its flattened body with inconspicuous scales tufts.

The series of non-exclusive characters that separate Hybovalgus from the other Oriental Valgina genera are:

- Protibial external teeth 1–3 long and sharp in males, where tooth 2 is sometime a bit shorter than 1 and 3; the same for females but often they are worn by digging (see remarks on page 7 about differences between the two sexes) and in some cases tooth 2 is slightly shorter than 1 or 3 ( Fig. 1 ).

- Both sexes have 5–6 protibial teeth.

- Suctorial brush long in males, short in females ( Ricchiardi & Li 2015). See remarks below about differences between the two sexes.

- Anterior margin of clypeus noticeably sinuate in both sexes, a bit less in females of H. thibetanus .

- Pronotal lateral margins more or less crenate in both sexes.

- Pronotal lateral margin depression always present in both sexes.

- Pronotal posterior margin of most females (but not all) more or less excavated.

- Parameres of Hybovalgus shape ( Fig. 3 ).

- Protibia with five teeth on the external margin, in one case six ( H. sexdentatus ).

- Pygidium of males always narrowed from the middle to the apex; apex rounded in caudal view, not prominent in lateral view. Pygidium of females often (but not always) modified at apex (see Remarks under species accounts below).

- Pygidium of males with a ventral small, flat or slightly hollowed surface with posterior margin rounded or pointed at center. In females this area is bigger and deeply hollowed.

- Pygidium of females without pygidial stylus.

- Propygidial scale tufts of females darker than those of males.

Some species have protibial teeth 1–2 and/or 3–4 closer to one another than to the others. This character is not consistent among all the specimens of Hybovalgus as it varies within the same species.

Another character that we decided not to use for the separation of species is the presence or absence of cretaceous maculae on the propygidium or pygidium of males. In some species those maculae are really difficult to see because they are covered with thick scales or by the built-up body grease.

Identification of females

Generally, it is easy to separate females from males because the pronotal posterior margin is more or less deeply excavated ( H. bioculatus , H. fraternus , H. thibetanus , H. tonkinensis ) and/or the apex of the pygidium is modified into a pointed projection ( H. fraternus , H. sexdentatus , H. thibetanus , H. tonkinensis ), a rounded projection ( H. bioculatus ), or the apex is simply rounded ( H. calvus sp. nov.).

Often, females are larger than males. All the females we studied bear black propygidial scale tufts, even when their male counterparts have testaceous propygidial scale tufts.

Females of two species, H. fulvosquamosus and H. jordansi , are unknown.

Variability of paramere shape

After analysis of the males of a many Valgina belonging to hundreds of species, we concluded that the study of the shape of the parameres is a reliable way to define species. There are, however, a couple of notable exceptions. Jameson & Swoboda (2005), revising the New World Valgina , wrote that: “However, one species of New World valgine, Valgus seticollis Beauvois, 1807 , has extremely variable male genitalia although there is an overall similarity in pattern” ( Jameson & Swoboda 2005: figs 31–35); “Other characters that we examined are consistent within this species, including form of the tarsomeres, pygidial spine, pronotum, sternites, and spiracles. Lacking other morphological characters to separate the genitalic forms, we conservatively group all the forms as one species. A thorough study of the genitalic forms of V. seticollis would be an excellent topic for a molecular analysis and could reveal interesting evolutionary patterns”.

Kolbe (1897) described a new Valgina genus, Homovalgus , to include Valgus seticollis . Jameson & Swoboda (2005) clarified the nomenclature of the species and placed it under Valgus . It is our opinion that because the shape of the parameres is similar to that of Hybovalgus / Dasyvalgoides , and the lack of a pygidial stylus in females, this species must be separated from Valgus and that its valid name is Homovalgus seticollis . The relationships of this species to the Oriental Valgina could add appeal to further study.

In the Oriental Region, another species, Hybovalgus fraternus , is a similar case to that of Homovalgus seticollis . Hybovalgus fraternus also exhibits limited variation in morphology and great variation in paramere shape. This is why we decided to conservatively avoid splitting this species merely on the basis of variation in paramere shape.

Description of aedeagus

Figure 3 shows several examples of the aedeagus of Chinese Hybovalgus species along with some nomenclature. The outline of the aedeagus is distinctive. The phallobase is always V-shaped ventroapically (vs) and with a sclerotized upper anterior part (spb) notched, flat or pointed, sometime variable within the same species. The parameres are prominent, with the apex extended and with different shapes, with or without a sub-apical external or internal tooth; basal lobe more or less developed and in some cases variable in shape within a species. In lateral view the parameres shows a more or less deep, basomedial notch (bmn).

Distribution

Hybovalgus species are mostly distributed in south-central continental China, with most species extending to northern Laos, northern Vietnam, Hainan Island (5–6 species) and Taiwan. In Taiwan there are six species: Hybovalgus kamiyai (Sawada, 1941) ; H. major Sawada, 1939 ; H. matsudai Miyake, 1985 ; H. obsoletosquamosus Miyake, 1985 ; H. takasagoensis (Sawada, 1941) and H. thoracicus Moser 1911 . These six Taiwanese species are considered endemic, but their relationships with continental Hybovalgus must still be analyzed.

Figure 4 shows the approximate distribution of Hybovalgus species. In the west, the genus inhabits Yunnan and Sichuan (there are no records so far for Myanmar). In the east some species reach Shandong, Jangsu and Zhejiang. In the north there are extensions into the southestern part of Palaearctic China (sensu Chen et al. 2008). We found no records of Hybovalgus from Henan and Anhui provinces or Chongqing Municipality, but this may be due to a lack of collecting.

Summary of Chinese species distribution

Hybovalgus bioculatus Kolbe, 1904 : Laos, Vietnam, China (Hainan, Guangxi).

Hybovalgus calvus sp. nov.: Vietnam, China (Hainan).

Hybovalgus fraternus Moser, 1915 : Vietnam, Laos, China (Fujian, Zhejiang, Sichuan, Guangxi, Jangxi, Hunan, Guizhou).

Hybovalgus fulvosquamosus Moser, 1904 : Laos, Vietnam, China (Hainan, Hunan, Guangdong).

Hybovalgus jordansi ( Endrödi, 1952) : China (Fujian).

Hybovalgus sexdentatus Arrow, 1944 : Vietnam, Laos, China (Guangxi, Yunnan, Sichuan, Hainan, Shandong?).

Hybovalgus thibetanus ( Nonfried,1891) : China (Yunnan, Sichuan, Jangsu, Shaanxi, Jiangxi, Hubei, Gansu, Zhejiang).

Hybovalgus tonkinensis Moser, 1904 : Vietnam, China (Fujian, Zhejiang, Jiangxi, Guangxi, Hunan, Guizhou, Hainan, Gansu, Sichuan).

Figures

Fig. 3. Different shapes of aedeagus. A. Hybovalgus fraternus Moser, 1904. B. H. thibetanus (Nonfried, 1891). C. H. tonkinensis Moser, 1904. Proposed nomenclature of Hybovalgus aedeagus: aap = anterior apex of phallobase; ap = apex of parameres; bl = basal lobe; bmn = baso-medial notch; etp = sub-apical external tooth of parameres; iml = internal medial lobe; itp = sub-apical internal tooth of parameres; ma = membrane of aedeagus; pb = phallobase; spb = sclerotized upper anterior part of phallobase; vs = V-shaped ventro-apically membranous region of aedeagus. Drawings: grey parts: parameres; white parts: phallobase.

Fig. 1. Five-toothed protibia. A. LT ♂ of Hybovalgus fraternus Moser, 1915 (MNHUB). B. LT ♂ of Hybovalgus fulvosquamosus Moser, 1904 (MNHUB).

Fig. 4. Dotted area: approximate distribution of Hybovalgus. Original map from http://www.d-maps. com/pays.php?num_pay=77&lang=it.