Ancyronyx helgeschneideri Freitag & Jaech , 2007

Freitag, Hendrik & Balke, Michael, 2011, Larvae and a new species of Ancyronyx Erichson, 1847 (Insecta, Coleoptera, Elmidae) from Palawan, Philippines, using DNA sequences for the assignment of the developmental stages, ZooKeys 136, pp. 47-82 : 72-74

Ancyronyx helgeschneideri Freitag & Jaech, 2007 Figs 1019 A–L

Ancyronyx helgeschneideri Freitag & Jäch, 2007: 55-58 (adult description).

Material examined.

21 exs., 1L (0.45) (PCSD, SMTD, ZMUC, IMRL, CFP, NMW, ZSM [FR007, FR061]) "PHIL.: Palawan, P. Princesa S Manturon, Cabayugan R. 10°09'28"N, 118°53'26"E 05.3.2001, leg. Freitag (CR4)M"; 5L (0.39, 0.45, 0.48, 0.49, 0.50) (NMW) "PHIL.: Palawan, P. Princesa S Manturon, Cabayugan R. 10°09'16"N, 118°52'30"E 21.4.2001, leg. Freitag (CR3)C"; 4L (0.32, 0.37, 0.40, 0.43) (CFP) "PHIL.: Palawan, P. Princesa S Manturon, Cabayugan R. 10°09'16"N, 118°52'30"E 18.10.2000, leg. Freitag (CR3)M"; 2L (0.25, 0.48) (CFP) "PHIL.: Palawan, P. Princesa S Manturon, Cabayugan R. 10°09'16"N, 118°52'30"E 13.2.2001, leg. Freitag (CR3)C"; 1L (0.42) (IMRL) "PHIL.: Palawan, P. Princesa S Manturon, Cabayugan R. 10°09'16"N, 118°52'30"E 04.9.2000, leg. Freitag (CR3)C-P"; 3L (0.41, 0.46, 0.48) (ZSM) "PHIL.: Palawan, P. Princesa S Manturon, Cabayugan R. 10°09'16"N, 118°52'30"E 31.7.2001, leg. Freitag (CR3)C"; 2L (2 × 0.47) (PCSD) "PHIL.: Palawan, P. Princesa S Manturon, Cabayugan R. 10°09'28"N, 118°53'26"E 04.9.2000, leg. Freitag (CR4)C-R"; 5L (SMTD) "PHIL.: Palawan, P. Princesa S Manturon, Cabayugan R. 10°09'28"N, 118°53'26"E 16.10.2000, leg. Freitag (CR4)C";1L (0.46) (ZMUC) "PHIL.: Palawan, P. Princesa S Manturon, Cabayugan R. 10°09'28"N, 118°53'26"E 25.5.2001, leg. Freitag (CR4)D"; 1L (0.32) (NMW) "PHIL.: Palawan, P. Princesa SE Manturon, Karst spring 10°09'29"N, 118°53'30"E 18.10.2001, leg.Freitag (LS4)C"; 1L (0.45) (ZMUC) "PHIL.: Palawan, P. Princesa SE Manturon, Karst spring 10°09'29"N, 118°53'30"E 09.12.2001, leg.Freitag (LS4)C"; 2♂♂, 1♀ (SMTD, CFP) "PHIL.: Palawan, Rizal, Campung-ulay, Kalitawan Riv.; HW km 212.2, sec. veget/forest; slightly polluted, submerged wood in run, c. 30m asl. 9°19'11"N, 118°22'35"E 02.7.2010, leg. Freitag (186)"; 1♂, 2♀♀ (NMW, ZSM: [FR013])"PHIL.: Busuanga, Coron; Guadelupe, Balolo R./Brdg. Nat.Rd. km 14; lowld. creek; sec.veget.; run, gravel, CPOM, c.10m asl, 12°01'43"N, 120°06'48"E 03.2.1995, leg. Freitag (169)M".

Larval diagnosis (based on 6th instar).

Colour as in Fig. 10; dorsal head, pronotal disc and abdominal segment IX from apical 0.1 to apical 0.4 dark brown; lateral head, antennae, anterior and lateral pronotal margins, legs (except for tip of claw), lateral abdominal, meso- and metathoracic margins including projections as well as median portion of segment IX pale yellowish; anterior pronotal edges with conspicuous pale pattern that is extending mediad to disc; remaining parts of dorsal thorax and abdomen brown with indistinct pale patterns; the latter most conspicuous as yellowish spot at posterosagittal margin of all segments. Ventral side entirely pale, except for pale brown gula, maxillae, labium and ventral parts of genae.

HW c. 0.50 mm, entire larve up to 4.5 mm long. Body shape somewhat similar to that of Ancyronyx procerus in the external characters, except for the following characters: spiracles distinctly larger, very prominent (Figs 10, 19A); entire lateral margin with distinct long, trichoid setae (Figs 10, 19F); tubercles at dorsal side more prominent (Figs 19A, B), but dorsal setae very short.

Head (Figs 19 B–E) broadest subbasally, slightly conical anteriad, without median pointed projection at frons; pair of sublateral anterior projections between antenna and clypeus rather shallow and inconspicuous (Fig. 19B). Frons moderately densely covered with moderately large and equally dispersed setiferous tubercles; genae rugose, with scattered tubercles; lateral glabrous area with stemmata irregularly shaped. Antenna (Figs 19 B–D) short, c. 1/3 as long as head. Scape short, as long as broad, with subapical fringe of stout sensilla; pedicel cylindrical, less than two times as long as scape and c. three times as long as broad, with few inconspicuous apical sensilla; flagellum and sensorium as in Ancyronyx procerus . Labrum (Fig. 19C) c. 2.5 times as wide as long; lateroapical edges rounded; dorsal surface with tubercles, ramose setae and short trichoid setae. Ventral head (Figs 19D, E) with well-developed longitudinal crests. Maxilla (Figs 19D, E) almost as in Ancyronyx procerus . Labium (Figs 19D, E) with mentum (postmentum) broadest in apical half, one pair of moderately long trichoid setae inserted sublaterally at anterior 0.25; some additional inconspicuous setae present at lateral margin in apical half; pair of apicolateral teeth slender, inserted at a distinct subapical crenation; submentum (prementum) divided.

Prothorax slightly broader than long; tergum with irregularly shaped signa in posterior half. Venter of pro-, meso and metathorax (Fig. 19F) similar to that in Ancyronyx procerus , but anterior sclerites more oblique.

Legs as in Figs 19F, G and very similar to those in Ancyronyx procerus .

Abdomen (Figs 10; 19A, G–L) with terga slightly depressed groove along sagittal line at least from 1st up to 4th segment; venter almost glabrous, with scattered trichoid setae of different length; segment IX as in Figs 19 J–L with emarginate apex; operculum (Fig. 19L) glabrous, with rather inconspicuous basal ridges; disc without conspicuous asperities, covered with few scattered setae.

Variation between larval instars.

Specimens of the 3rd to the 6th (final) instar stage are available for study. Within this range it is obvious that the younger the specimens the paler they are, the longer are all kinds of setae (in relation to the body) and the fewer setiferous asperities are present. Additionally, the limb setae are varyingly arranged and the terminal abdominal segment is relatively shorter and broader as well as the legs. The latter is most obvious between the final and prefinal instar stages.

Larval differential diagnosis.

The larvae of Ancyronyx helgeschneideri resemble those of Ancyronyx procerus but can be clearly distinguished by absence of the pointed projections at median frons, the more shallow projections between the antenna and clypeus, the larger and more protruding spiracles, the more convex head shape, the varying labrum and antennae and the dorsal surfaces of head, thorax and abdomen that are densely covered with larger tubercles as well as the entire lateral body margin bearing long, conspicuous setae.

Distribution.

Only known from Palawan and Busuanga.