Peschetius bistroemi, Sheth & Ghate & Dahanukar & Hájek, 2021

Sheth, Sayali D., Ghate, Hemant V., Dahanukar, Neelesh & Hajek, Jiri, 2021, Integrative taxonomic review of the genus Peschetius (Coleoptera, Dytiscidae, Hydroporinae) from India with description of two new species, Arthropod Systematics & amp; Phylogeny 79, pp. 535-553 : 535

3.3.1. Peschetius bistroemi sp. nov.

Figs 5A , 6A , 7A , 8A

Specimens examined.

Holotype: INDIA • ♂; Kerala, Kottayam district, Pambady; 9°35′21″N, 76°34′59″E; ca 10 m. a.s.l.; 7 Jan. 2020; S. D. Sheth leg.; streamlet; Indian Council of Agricultural Research , Bengaluru, India [ICAR] . Paratypes: INDIA - Kerala • 1 ♀; same data as holotype; ZSIP • 1 ♂, 1 ♀; Mukkada ; 9°28′7″N, 76°47′43″E; ca 100 m. a.s.l.; 7 Jan. 2020; S. D. Sheth leg.; streamlet; UASB • 1 ♂; Aimcombu ; 9°46′16″N, 76°41′39″E; ca 50 m. a.s.l.; 7 Jan. 2020; S. D. Sheth leg.; streamlet; HVGC.

Description of male holotype.

Habitus: Body elongate, widest before midlength of elytra; lateral outline of body discontinuous with distinct angle between pronotum and elytra; elytral keels prominent (Fig. 5A ). - Colouration: Head ferruginous. Appendages testaceous. Pronotum ferruginous, with bilobed black band near posterior margin. Elytron blackish with typical testaceous markings consisting of two subbasal spots, premedian and postmedian transverse bands, and preapical spot; testaceous spot near humeral angle of elytra reduced. Ventral side overall testaceous. Prosternum darker along anterior margin, prosternal process with black border. Metaventrite darker apically, posterior margins of abdominal ventrites darkened. Coxae ferruginous. - Head: Transverse (broader than long), eyes slightly emarginate. Antennae with antennomeres IV and V markedly globular and swollen, ventrally flat; antennomeres VI and VII broader, ventrally flat. Width across eyes is 2X the width between eyes. Clypeus arcuate. Labrum emarginate with series of setae on anterior margin. Punctation of head dense, distance between punctures smaller than puncture diameter. Punctures fine on clypeus, becoming progressively coarser posteriorly on frons, occipital part posterior to eyes impunctate. Setiferous punctures present in well-developed fronto-clypeal depressions and as a row along inner margin of eyes. Reticulation consisting of polygonal, slightly transverse meshes on clypeus; posterior part of frons smooth. Impunctate occipital part posterior to eyes distinctly microreticulate. - Pronotum: Transverse. Anterior margin straight, sides almost straight, curved anteriorly, posterior margin gently sinuate; anterior corners acute, posterior margins obtuse. Pronotal disc with posterior depression prominent. Pronotum with distinct depressions between disc and sides, mediolaterally between disc and posterior margin. Pronotal disc strongly vaulted. Punctation dense, distances between punctures smaller than puncture diameter. Punctures setiferous, finer on disc, becoming coarser on margin and sides. Surface between punctures microreticulate with shallowly impressed polygonal meshes visible on either side of disc. - Elytra: Widest before midlength, keels prominent. Punctation of elytra coarser than on head and pronotum. Punctation dense, distance between punctures smaller than puncture diameter. Punctures finer along suture, costae and lateral margin, coarser on disc. Surface between punctures microreticulate with well impressed polygonal meshes. - Legs: Tibiae club-shaped, dorsally with long natatorial setae; pro- and mesotarsi broadened, dorsally with long natatorial setae, ventrally with adhesive setae; metatarsi with long natatorial setae on both sides. - Ventral side: Prosternum sinuate on anterior margin, portion between procoxae narrowed. Prosternal process broad anteriorly, narrowed posteriorly, without transverse depression and without keel but slightly raised (Fig. 7A ). Mesoventrite bifurcated on anterior margin, posterior margin rounded. Metaventrite with coarse punctures, distance between punctures almost equal or larger than puncture diameter. Surface microreticulate with shallowly impressed polygonal meshes. Anterior border of metaventrite with two shallow but distinct depressions below mesocoxae. Metacoxal plate with coarse punctures. Distance between punctures smaller than puncture diameter. Reticulation similar to that of metaventrite. Metacoxal process raised. Abdomen with five ventrites (V1 to V5); V1 with 6-10 while V2 with 2-5 macropunctures arranged in two rows on either side. V2 to V5 covered with setigerous punctures; V3 to V5 with distinct lateral depression; depression on V3 less prominent; reticulation of V2 to V5 consists of polygonal meshes. Punctures on ventral surface setiferous. - Male genitalia: Median lobe broad at base and narrowed towards apex, gently curved, and with a basal process (Fig. 6Aa). Parameres with long setae in apical half, apex rounded (Fig. 6Ab).

FEMALE. As male but antennomeres simple, not modified. Pro- and mesotarsi slender or less broadened. Spermatheca as in (Fig. 8A )-spermathecal spine long and slender.

Measurements (N =10). Body length 2.95-3.20 mm (holotype: 3.04 mm) and maximum width 1.65-1.85 mm (holotype: 1.72 mm). See also Supplementary file 4.

Variability.

The specimens of type series are uniform with slight variation in elytral maculation.

Differential diagnosis.

Peschetius bistroemi sp. nov. is easily recognised from all known Peschetius species based on distinctly broadened antennomeres IV and V in males-a character unique within the genus Peschetius . With nearly a flat prosternal process (i.e. without transverse depression or longitudinal keel), the new species is similar and probably related to P. taprobanicus from Sri Lanka; however, it differs from the latter species in the shape of male genitalia: the apex of median lobe is not bent as in P. taprobanicus and the curvature of the median lobe of P. bistroemi sp. nov. is shallower. The parameres of P. bistroemi sp. nov. are abruptly narrowed and rounded at their apex while in P. taprobanicus those are gradually narrowed. The setae of the parameres are present in the apical half in P. bistroemi sp. nov. while in P. taprobanicus these are restricted to the apex. Further, the spermathecal spine in P. bistroemi sp. nov. is longer than the other three Indian species, and not curved like that in P. nilssoni sp. nov.

Etymology.

The species is named in the honour of Prof. Olof Bistrӧm (Helsinki, Finland) for his significant contribution to the taxonomy of Dytiscidae , including the genus Peschetius . The name is a noun in the genitive case.

Collection circumstances.

The specimens were found in slow flowing streamlets with rock and mud as substratum, and decaying leaves.

Distribution.

The species is so far known only from three close localities in Kottayam district, Kerala, southwestern India.

Figures

Figure 5. Dorsal habitus of Indian Peschetius. A P. bistroemi sp. nov. (Holotype) B P. nilssoni sp. nov. (Paratype- a longitudinal spot, b transverse spot; Amboli, Maharashtra) C P. quadricostatus (Amboli, Maharashtra) D P. toxophorus (a uninterrupted transverse band; Kotagiri, Tamil Nadu). (Body length: A 3.04 mm, B 3.15 mm, C 3.40 mm, D 3.35 mm).

Figure 6. Male genitalia of Indian Peschetius (a. median lobe; b. paramere; bx. tapering of paramere). A P. bistroemi sp. nov. (holotype) B P. nilssoni sp. nov. (holotype) C P. quadricostatus (Jejuri, Maharashtra) D P. toxophorus (Satara, Maharashtra). Scale bars: 100 µm (A, B, C, D).

Figure 7. Prosternal process of Peschetius. A P. bistroemi sp. nov. (paratype; Mukkada, Kerala) B P. nilssoni sp. nov. (paratype; Jejuri, Maharashtra). Scale bars: without scale.

Figure 8. Female spermatheca of Indian Peschetius. A P. bistroemi sp. nov. (paratype; Mukkada, Kerala) B P. nilssoni sp. nov. (a spermathecal spine; paratype; Ane, Maharashtra) C P. quadricostatus (Ane, Maharashtra) D P. toxophorus (a spermathecal spine; Satara, Maharashtra). Scale bars: 100 µm (A, B, C, D).