Hydrodessus amazonensis Spangler, 1966

Miller, Kelly B., 2016, Revision of the Neotropical diving beetle genus Hydrodessus J. Balfour-Browne, 1953 (Coleoptera, Dytiscidae, Hydroporinae, Bidessini), ZooKeys 580, pp. 45-124 : 54-57

Taxon classification Animalia Coleoptera Dytiscidae

Hydrodessus amazonensis Spangler, 1966 Figs 2, 44

Hydrodessus amazonensis Spangler, 1966: 380; Young 1969: 2; 1970: 157; Spangler 1985: 89; Biström 1988: 37; Nilsson 2001: 236.

Type locality.

Peru, near Ituitos, from the Amazonas.

Diagnosis.

This species is difficult to diagnose from others since specimens were not available for examination, but based on the description and illustrations by Spangler (1966) the species is elongate with broadly curved lateral pronotal margins (Fig. 2A), the elytra are patterned with testaceous and dark reddish-brown maculae (Fig. 2B), and the lateral elytral carina extend about 1/3 × length of elytron. The male genitalia in lateral aspect were illustrated by Spangler (1966). The median lobe is elongate triangular basally, relatively evenly curved medially with the apical portion straight and slender and the apex abruptly constricted and extremely slender and pointed (Fig. 2B). The lateral lobe is moderately narrow with the dorsal margin straight for most of its length and the apex rounded (Fig. 2C). The overall shape, color pattern and male genitalia should allow for specimens to be identified in the future.

Description.

Measurements. TL = 2.85 mm, GW = 1.25 mm. Body elongate, apically pointed, lateral outline strongly discontinous between pronotum and elytron (Fig. 2A).

Coloration (Fig. 2A). Head and pronotum testaceous. Elytra testaceous except dark reddish-brown medial stripe along suture, one incomplete transverse band basally, one complete transverse band medially, and a small lateral macula at apical 1/5 (Fig. 2A). Antennae, palps legs, and venter testaceous.

Sculpture and structure. Head finely, densely punctate, punctures separated by 1 × puncture diameter or less; anterior clypeal margin arcuately emarginate; labrum finely, densely punctate and finely alutaceous, margin narrowly emarginate; anterior margin fringed with setae. Pronotum broadly rounded, widest anterior of middle (Fig. 2A); fine lateral bead present throughout length; surface densely, moderately coarsely punctate, punctures larger than on head, separated by <1 × puncture diameter. Elytra elongate, apically pointed (Fig. 2A); lateral carina distinctive, extending about 1/3 length of elytron; surface microreticulate, appearing granulose and with few, fine punctures similar to pronotum. Prosternal process very slender between procoxae, apical portion 2 × width between procoxae, weakly concave longitudinally. Metaventrite microreticulate, granulose. Legs finely granulose; pro- and mesotibiae moderately broad; metatrochanter swollen apically; metacoxa microreticulate. Abdomen microreticulate, granulose.

Male genitalia. Median lobe in lateral aspect strongly curved medially, apical portion slightly curved, abruptly narrowed along dorsal margin subapically, apex narrowly pointed and slightly curved (Fig. 2B); lateral lobe in lateral aspect moderately broad in basal portion, apex slightly narrowed and straight to broadly rounded apex, with series of setae along medial surface apically (Fig. 2C).

Female genitalia. Females not described by Spangler (1966).

Sexual dimorphism. Male pro- and mesotarsi I–III more broadly expanded than female and ventrally with several large adhesive setae; female with sublateral carina absent basally.

Variation. According to Spangler (1966), specimens differ somewhat in size and coloration with some specimens having the dark coloration reduced or more enlarged. The presence of the sublateral carina is also variable, and it is absent in some specimens.

Distribution.

This species is known only from the type locality near Iquitos, "from the Amazonas," Peru. (Fig. 44).

Habitat.

Nothing is known of the natural history of this species.

Discussion.

The specimens on which this species (and Hydrodessus nanayensis Spangler) were based were collected during the Catherwood Foundation expedition to Peru. The type material was not found in either the ANSP, where Spangler indicated the holotype was deposited (J. Weintraub, pers. comm.), the MZCZ (where many ANSP Coleoptera types were sent), or the USNM (where Spangler was working). Illustrations of the habitus and lateral aspect of the male genitalia are provided (redrawn in Fig. 2B,C), and the description of the species is extensive, though it excludes a number of important diagnostic features. The description presented here is based on Spangler’s (1966) description and his figures and later keys ( Spangler 1985; Young 1970). The extremely curved lateral margins of the pronotum, the distinctive color pattern on the elytron, and the shapes of the male genitalia are distinctive (Figs 2B, C), but Hydrodessus amazonensis does not appear to correspond to any specimens examined during this study. Spangler (1966) indicates that the fine sublateral elytral carina is present in only two specimens he examined, the holotype and one other, suggesting that perhaps the series was mixed.

Specimens.

No specimens were examined of this species, and the treatement here is based on the description by Spangler (1966).