Protistolophus secundus, Vorst, 2024

Vorst, Oscar, 2024, A second species of Protistolophus Short from Peru (Coleoptera: Hydrophilidae: Hydrophilinae), Zootaxa 5537 (3), pp. 445-450 : 446-449

Protistolophus secundus sp. nov.

Holotype ♂ ( MUSM): “PE: San Roque, 7.3 km NW of | 6.325°S 76.461°W Pe31C | 27.i.2015 1328 m | leg. O. Vorst | Brooklet, prim. forest”, “ Holotypus | Protistolophus ♂ | secundus Vorst ” [red label] ( MUSM) . Paratypes ( MUSM, RMNH): 3 ♂♂, 1 ♀, 2 exs.: same data as holotype ; 1 ♂, 1 ex: “ Peru, San Roque , 6.8 km NW of, 6.328°S 76.458°W, 1300 m, 28.i.2015, brook in primary forest, leg. O. Vorst ” ; 1 ♂: “ Peru, San Roque , 6.385°S 76.430°W, 596 m, 18- 20.i.2015, trickle in forest, leg. O. Vorst ” .

Diagnosis. Middle sized hydrophilid (ca. 8 mm), easily recognizable as a Protistolophus by the presence of a sternal keel in combination with sutural striae on the elytra. Habitus similar to that of P. splangeri , the only other known species of the genus, but overall somewhat more stocky, with the pronotum more transverse. It also differs from P. spangleri by the simple fifth ventrite lacking an emargination, the emarginated labrum and by the characteristic aedeagus of the male.

Description. Body length: 8.0– 8.6 mm (median 8.25 mm, N = 6), body width: 4.1–4.4 mm (N = 4). Body shape oval, widest at about 1/5–1/6 of the elytral length ( Fig. 1, 2 ).

Colouration. Dorsum shiny, almost entirely very dark brownish black, somewhat chestnut brown towards the edges of pronotum and elytra, notably so in lateral and lateroposterior margins of the pronotum. Legs chestnut brown, somewhat lighter apically. Labrum, mandibles and maxillary palps chestnut brown.Antennae chestnut brown, somewhat lighter basically. Venter largely dark chestnut brown; pseudepipleura, epipleura, lateral hypopleuron of pronotum as well as lateral margin of abdominal ventrites slightly lighter.

Punctation. Dorsal ground punctation fine but clearly visible on the head, much smaller on the pronotum, almost indiscernible on the elytra. Systemic punctures present on head, pronotum and elytra. Labrum with sparse punctures, loosely arranged in a transverse row; on the clypeus punctures arranged in an arc anterior to the eye; frons with several punctures close to the eye; at some distance from the inside of the eye with a pit resulting form the fusion of several punctures. Pronotum on each side with sparse anterior and posterior arc of ca. 4–7 punctures. Elytra with inner four rows of 8–10 punctures, a fifth row directly adjacent to the outer margin carrying ca. 50 punctures. Venter in large part pubescent, however rather coarse and thin especially on the abdomen.

Head. Antennae with nine segments, antennal club pubescent three-segmented. Clypeus with anterior margin emarginated. Maxillary palps moderately long, about as long as the width of clypeus anterior of the eyes; apical segment ca. 1.3 x as long as penultimate. Mentum subrectangular with rather coarse punctation.

Thorax. Pronotum with narrow bead along lateral margins, continued into a much finer bead along anterior and posterior margins, absent in the middle part of the posterior margin. Hypomeron with lateral margins broadly glabrous. Prosternum with elevated median carina carrying rather long erect hairs along the whole length. Mesoventrite with a strongly raised laminar keel posteriorly elongated into a long spine reaching halfway the metaventrite, fused with the median elevation of the metaventrite forming a sternal keel. Furcasternum glabrous. Pseudepipleura glabrous, epipleura with rather thin pubescent punctation. Elytra with sutural stria in posterior half. Scutellum slightly longer than wide. Legs with femoral pubescence restricted to the base. Hind femora with pubescence on the posterior margin reaching halfway the trochanter, along the anterior margin extending to 2/5 of the length of the femur.

Abdomen. Abdomen with five visible ventrites. Last visible ventrite regularly curved, without emargination.

Aedeagus. Length ca. 1.6 mm, following the basic hydrophilid ground plan ( Fig. 3, 4 ). Basal piece about as long as the parameres. Parameres slightly bent inward, with a small apicolateral notch and three apical bristles. Penis strongly broadened apically.

Distribution. Currently known from three nearby locations in the Cordillera Escalera northwest of San Roque de Combaza ( Peru: Departamento de San Martín), 6.33°S 76.46°W.

Habitat. Most specimens came from samples collected from two brooklets. Both brooklets are situated in submontane primary forest at an altitude of ca. 1300 m a.s.l. and are about 0.5 km apart. The first brooklet had a width of ca. 2 m and clear, fast-running water on a substrate of larger stones ( Fig. 5 ), sand and loam, but also included several more pond-like tracts filled with leaf litter, with almost stagnant water ( Fig. 6 ). A simple portable instrument was used to determine temperature (19°C), pH (4.7) and electrical conductivity (46 μS/cm). The second brooklet with a width of ca. 1 m and brown slow-running water on a sandy substrate ( Fig. 7 ) produced two specimens. The third collecting site was 7 km to the southeast and consisted of a loamy trickle in secondary forest close to the Rio Combaza at an altitude of 600 m a.s.l. ( Fig. 8 ).

Etymology. The species name is derived from the Latin secundus , meaning second. It is to be treated as an adjective.

Figures

FIGURES 1–2. Habitus of Protistolophus secundus sp. nov., holotype male, dorsal (1) and ventral (2) aspect. Scale bar 2 mm. Photographs by Yvonne van Dam.

FIGURES 3–4. Aedeagus (3) of Protistolophus secundus sp. nov., holotype, and detail (4). Scale bar 0.5 mm.

FIGURES 5–8. Collecting sites of Protistolophus secundus sp. nov. in the Cordillera Escalera. Brooklet in primary forest (5) with pond-like tracts (6); slow-running brooklet in primary forest (7); loamy trickle in secondary forest (8).