Parallidiostoma tricornum Ocampo & Colby

Ocampo, Federico C. & Colby, Julia, 2009, Parallidiostoma tricornum Ocampo and Colby, a new genus and species of Allidiostomatinae from Peru (Coleoptera: Scarabaeidae), Zootaxa 2287, pp. 64-68 : 66-68

Parallidiostoma tricornum Ocampo & Colby new species

( Figs. 1–6 )

Diagnosis. Parallidiostoma tricornum is distinguished from other species in the Allidiostomatinae by the characters listed in the generic diagnosis (males). Females are unknown for this species. Male genitalia are also diagnostic ( Fig. 4 ).

Description. Holotype. Length 8.2 mm, width 4.5 mm. Color reddish brown. Head ( Figs. 1–3 ): Surface punctate; punctures large, dense. Frons bearing a large horn, horn base half as wide as head; horn curved, surface punctate at base. Frontoclypeal suture evident. Clypeus broadly rounded. Eyes slightly visible on dorsal view. Pronotum ( Figs. 1–3 ): Surface punctate, punctures moderate in size, moderately dense to sparse. Each pronotal anterior angle with a large horn; horns slightly convergent on each other; each horn with 1 fovea on outer edge. Area between horns with deep median fovea, fovea extending posteriorly; basal half of pronotum with 1 large tubercle on each side in center near basal margin, on either side of central fovea. Fovea impunctate to sparsely punctate. Elytra ( Fig. 1 ): with 10 well-defined punctate striae. Psudoepipleura poorly developed. Ve n te r ( Fig. 4 ): Proepisternum with longitudinal carina; carina setigerous; setae long, slender. Mesoepiesternum and metaepiesternum punctate; setae, moderate in length. Metasternum smooth medially, sparsely punctate on sides. Pygydium: surface punctate, setigerous; setae tawny, moderate in length. Legs: Protibia tridentate; teeth well developed. Protibial spur well developed, curved. Tarsi with taromeres 1-4 subequal in length, tarsomere 5 longer than tarsomere 4. Tarsal claws simple, shorter than tarsomere 5. Mesotibia and metatibia with strongly expanded at apex, with 2 spurs; spurs longer than tarosomeres 1 and 2 combined, curved. Metatarsus folds between metatibial spurs. Male genitalia ( Fig. 4 ): Parameres longer than phallobase, slender, curved.

Paratype. The single paratype specimen (male) does not differ from the holotype except slightly in length (8.3 mm).

Female. The female of this species is unknown.

Type material. Holotype male at IAZA labeled: “Limantambo/An/Cus; 13°29’43”S / 72°27’50”O / 28.09.2002 / 2700m / A. Bustamante N.” (typed) “ Parallidiostoma / tricornum / Ocampo & Colby / HOLOTYPE ” (handwritten). One partype at USNM labeled: “ PERU: Cuzco / 15 km SW Limantambo / 24 Feb. 1979 / W. E. Steiner.”(typed); “ Parallidiostoma / tricornum / Ocampo & Colby / PARATYPE ” (handwritten).

Distribution ( Fig. 5 ). Peru, Cuzco, Limatambo (80 km W Cuzco). These specimens were collected at 2700 m, in a dry montane forest.

Natural history. Little is known about the natural history of P. tricornum (and allidiostomatines in general), with the exception that they are attracted to lights. The larva of this species is unknown. Some allidiostomatines are known to stridulate using the transverse, striated surface of the outer half of the hind coxa ( Fig. 6 a) against a ridge in the first abdominal sternite, which also has a concavity that presumably acts as a sound amplifier ( Arrow 1904) ( Fig. 6 b). This structure is found in Allidiostoma and Parallidiostoma .

Temporal distribution. February (1); September (1).

Remarks. The paratype specimen is damaged. The head, pronotum with prolegs, and elytra are mounted on a card, while the rest of the specimen is preserved in two glycerin filled vials, pinned beneath the card. The genitalia are missing.

Figures

FIGURES 1 – 3. Parallidiostoma tricornum Ocampo and Colby, new genus and species, dorsal view of the holotype, fronto-dorsal and frontal views of the paratype.

FIGURES 4 – 6. Parallidiostoma tricornum Ocampo and Colby, male genitalia (4); distribution (5); matacoxa (cx) (6 a) and abdominal sternites 1 – 3 (st 1 – st 3), showing the stridulatory organ (arrows) (tr: metatrochanter, fem: metafemur) (6 b).