Ancyronyx schoedli Freitag & Kodada, 2017

Freitag, Hendrik & Kodada, Ján, 2017, Larvae of Ancyronyx Erichson, 1847 (Insecta: Coleoptera: Elmidae) from Sulawesi, using DNA sequences for the assignment of the larval stages, Zootaxa 4299 (1), pp. 121-130 : 124-126

Ancyronyx schoedli Freitag & Kodada, 2017

( Figs 2 A; 3A–F)

Material examined. 4LL ( CKB [SEM], CFM [FR128, FR129]): “ INDONESIA: Sulawesi, T. Toraja , Salu Toriu River , 810m asl ., c. 02°56′38′′ S 119°52′24′′E 0 2 Jan.1998 leg.Freitag (Sul8Af)”; 1L (NMW): “S - SULAWESI 1992 Malino-Manipi 700m (31) leg. Jäch 1.V. ”.

Larval diagnosis (based on presumably fifth instar, HW: 0.30 mm). Body elongate, nearly semicircular in cross section, dorsally vaulted, ventrally almost flat. Posterolateral margins of abdominal segments I–VII moderately produced ( Fig. 3 C). Colour ( Fig. 2 A) dorsally dominantly dark brown except for pale brown to yellowish lateral portion of head, apex of the terminal abdominal segment (up to posterior 0.15) and the entire first and eight abdominal segments; clypeus and labrum reddish brown; legs, antennae, remaining mouthparts, entire ventral side including operculum and except abdominal segment IX yellowish to pale brown.

The larva is very similar in the external characters to that of A. minerva (see Freitag & Balke 2011), except for the following characters: lateral abdominal projections ( Figs 3 C, D) with two large robust long setae (referred to as “trichoid teeth” in Freitag & Balke 2011), one robust short seta and one long thin trichoid seta. Dorsal tubercles slightly elevated ( Figs 3 A–D).

Head ( Fig. 3 A) widest at posterior 0.3, sides arcuate in posterior half; frontal suture V-shaped, conspicuous in wet specimens; dorsolateral portion with three pairs of conspicuous setae: first pair consists of short setae situated mediofrontally, second pair of moderately long setae inserted near the frontoclypeal suture and third pair of long setae originate near frontal suture behind the eyes; lateral portion with about 4 pairs of moderately long setae. Antennae moderately long, overreaching anterior margin of labrum; setae of scapus trichoid. Labrum with subapical fringe of ramose setae and few trichoid setae laterally. Maxillary palpus ca. as long as stipes wide. Mentum subrectangular, slightly narrower along posterior 0.1–0.4; pair of trichoid setae moderately long, not reaching anterior margin, inserted sublaterally at anterior 0.35 of mentum.

Pro- meso- and metathorax subtrapezoidal, slightly narrowed anteriorly, broader than long; with slightly produced lateral rim; lateral rim with few scattered long trichoid setae; dorsosagittal carinae small, narrow and present at anterior half of mesonotum; surface of meso- and metanotum with microtubercles; pronotum with ca. six pairs of rather inconspicuous, irregularly shaped and partly fused signa (flat, subglabrous areas) in posterior half ( Figs 3 A, B); remaining areas of pronotum including anterolateral grooves with setiferous tubercles. Ventral sclerites of thorax granulose.

Abdomen ( Figs 2 A, 3C–F) without dorsosagittal carina, with distinct mesal suture except for segment IX ( Figs 3 C, E); lateral rim with few scattered long, trichoid setae; squamose setae at posterior rim of segments large; ventral sclerites of segment I with rather indistinct sagittal ridge in anterior half; segment IX ( Fig. 3 E) moderately short, ca. 1.6 times as long as wide; basomedian portion tuberculate, apical portion rugose; apex slightly emarginated; operculum ca. 1.7 times as long as wide.

Figures

FIGURE 2. Habitus of Ancyronyx larvae from Sulawesi, A: A. schoedli (body length 2.90 mm), B: A. skalei (body length 2.65 mm), C: A. tobada (body length 2.95 mm), D: A. longiparamerus (body length 2.95 mm), E: A. toraja (body length 3.30 mm), F: A. henningi (body length 2.35 mm).

FIGURE 3. Ancyronyx schoedli, larva, dorsal (SEM photographs), A: head and pronotum; B: detail of pronotum with asperities and tubercles; C abdominal segments I – IV; D detail of abdominal segment III with lateral abdominal projections and setae; E: abdominal segment IX; F detail of abdominal apex.