Platydracus

Pietrykowska-Tudruj, Ewa & Staniec, Bernard, 2012, Comparative larval morphology of Platydracus and Staphylinus (Staphylinidae: Staphylinini: Staphylinina) with notes on their biology and redescription of the pupa of Staphylinus, Zootaxa 3580, pp. 24-42 : 26-28

Platydracus

Generic diagnosis of mature larvae. The diagnostic characters of the genus Platydracus were determined based on morphological data extracted from the following respective descriptions: P. tomentosus ( Schmidt 1994) , P. maculosus —limited data ( Grebennikov & Newton 2009), P. stercorarius —very limited data ( Kasule 1970), P. zonatus —very limited data ( Newton 1990). The combination of characters that allow for distinguishing the known mature larvae of Platydracus from closely related genera within tribe Staphylinini are following: frayed setae on abdomen present; nasale with nine teeth; apotome with stalk and 3 or 4 pairs of setae; mandible with two setae; maxillary and labial palp three- and two-segmented, respectively; antenna with acorn-shaped sensory appendage; stipes of maxilla with hair-like cuticular processes; mala finger-shaped more than 2.5 times as long as wide, with two setae; sides of hypopharynx sclerotized; foretibia without comb or bifid setae; tarsungulus bisetose; cervicosternum triangular divided at least partially; paratergites and parasternites on I abdominal segment not fused; urogomphi longer than pygopod.

Description of mature larva (L3) of P. latebricola (adult habitus and aedeagus as in Figs 61, 63, 64; larval habitus as in Figs 1–3 )

Body length: 16.3 – 20.0 mm (mean 17.8 mm); head width (HW1): 1.9 – 2.0 mm (mean 1.96 mm), head width (HW2): 2.1 mm; head length: 1.9 – 2.1 mm (mean 1.99 mm); pronotum width: 1.9 – 2.0 mm (mean 1.98 mm). Colour: head dark brown, mandibles almost black, antennae, maxillae, labium and legs amber colored, pronotum dark brown, meso- and metanotum brown with darker anterior line, abdominal tergite I light brown, remaining tergites and sternites almost colorless, body and urogomphi dirty white.

Macro and micro setae of head, thorax, some setae on abdominal segments simple ( Figs 7, 10 ); some setae on abdominal segments and on urogomphi rod-shaped and frayed apically ( Figs 8, 9, 11 ). Body elongated, cylindrical first abdominal segments narrower than second one, segments II – V more or less equal length then gradually narrowed to the terminal segment of the body ( Figs 1 – 3 ).

Head (Figs 12 – 13; 16, 19, 21, 23 – 25, 28, 29, 32 – 34, 38, 40): 1.1 times as wide as long, margins rounded moderately, widest about in the half length of the head; dorsal ecdysial lines bifurcate before half length of the head (Fig. 12). Epicranial part (E) with 6 macro setae located symmetrically and about 100 short setae located asymmetrically in relation to epicranial suture; posterior part (P) with six micro setae and two pores (Fig. 12). Each side of head with four stemmata in a cluster, three stemmata almost of equal size, the upper one slightly bigger than others (Fig. 13). Nasale (Na) with 12 macro setae located anteriorly and symmetrically, 23–24 micro setae located asymmetrically and a pair of glandular pits laterally (Gp); anterior margin of nasale with 9 teeth divided on to 3 indistinct clusters (one middle and two lateral), each cluster with 3 teeth, paramedian teeth (Pmt) equal in length with median tooth (Mt) (Fig. 16); within lateral teeth (Lt1 – 3) Lt1 biggest, remaining (Lt2, Lt3) equal in length. Ventral side of head with 54 – 60 micro setae located asymmetrically in relation to ventral suture (Fig. 19). Apotome (Ap) (Figs 19, 21) in broad outline triangular, behind a pair of tentorial pits forming stalk, distinctly extending beyond tentorial pits (Tp); with 8 setae, two pores and a pair of glandular pits (Gp). Reticulate miscrosculpture of head surface as in Fig. 12A.

Antenna (Figs 23 – 25) 4-segmented, length ratio of segments I – IV 1.0:2.4:3.2:1.6, respectively; segment I 1.5 as wide at the base as long; segment II 2.2 times as long as wide, with two pores (one dorsally, and one ventroapically); segment III 3.0 times as long as wide in the widest place, with three macro setae laterally, three sensory appendages (Sa) (one biggest acorn-shaped and two tiny) and one pore ventro-laterally (Figs 23, 24); segment IV about 2.8 times as long as wide, about 3.6 times as long as acorn-shaped sensory appendage of segment III, with 3 setae and 4 solenidia (So) apically (Fig. 23). Epipharynx (Fig. 28) with transverse row of 55 – 60 long cuticular processes. Mandible (Fig. 29) rather broad and short relatively, with 2 setae (upper one smaller than lower one) at the outer margin, 2 pores dorsally, long furrow along inner margin (shape-cracked) and 2 transverse, short sutures convergent to furrow in about half of length; inner margin with simple obtuse low tooth in about half of length (Fig. 29A). Maxilla (Figs 32 – 34): length ratio of cardo (Cd) and stipes (Stp) 1:1.8; cardo 1.3 times as long as wide bearing 1 seta ventro-laterally; stipes rectangular 3.7 times as long as wide with 8 setae (3 near outer margin, 3 near inner margin, and 2 near mala), 2 pores (1 ventro-apically, 1 ventrally) and regions of hair-like cuticular processes latero-basally (Figs 34, 34A). Mala (Ma) (Fig. 32) finger-shaped, slightly narrowed apically, with 2 setae (1 on inner margin, 1 ventrally), 3 sensory appendage apically (differ of length), and 2 pores ventro-basally; length ratio of mala and segment I of maxillary palp: 1.1:1. Palpifer (Pf) (Fig. 32) with 1 pore and 1 seta ventrally. Maxillary palp (Pm) 3-segmented; length ratio of segments I–III: 1:1.8:1.3, respectively; segment I 1.6 times as long as wide, slightly and gradually winded to its apical, with 2 pores ventrally; segment II 2.7 times as long as wide, distinctly winded to its apical, with 2 setae near apical (1 at the outer, 1 at the inner margin) 1 pore near apical; segment III distinctly narrower than others, 3.8 times as long as wide, with 1 digitiform sensory appendage basally on outer margin, 2 pores near apex and a few micro sensory appendages apically, length ratio segment and digitiform sensory appendage: 3.8:1 (Fig. 33). Hypopharynx: majority of dorsal side of labium membranous and thickly pubescent, sides sclerotized with a pair of pores (Fig. 38). Prementum (Fig. 40) consists of two parts: anterior–triangular, membranous with ligula (Lg) and a pair of labial palps, and posterior–almost square, sclerotized, with 4 long setae (2 anteriorly, 2 medially); ligula button-like, with a few pores and 2 setae, separated from prementum by sclerotized stripe. Labial palp (Lp) 2-segmented (Fig. 40); length ratio of segments I – II 1.7:1, respectively; segment I widened about in half of length, 1.6 x as long as wide at the widest place, with 1 pore near inner margin; segment II distinctly narrower than the first one, gradually narrowed to the apical, 2.2 as long as wide in the widest place, with one pore near apical and a few micro sensory appendages apically (Fig. 41).

Thorax ( Figs 43, 45, 47 ). Foreleg ( Fig. 43 ): trochanter ( Tr) with 17 setae (2 thick, spine-shaped near ventral margin) and a few pores located along of transversal line in half of its length; femur (Fe) stocky widened in the apical part with 62 setae (18 thick, spine-shaped) and 3 pores; tibia (Tb) short relatively with 40 setae (7 thick, spine-shaped in its apical part) ( Figs 43, 43 A); tarsungulus (Tu) short relatively, with 2 small setae ( Fig. 43 B); length ratio of protrochanter, profemur, protibia and protarsungulus 3.1:4.7:2.8:1, respectively. Pro-, meso-, and metanotum with mid-longitudinal ecdysial line; each thoracic tergites with a pair of sensilla anteriorly (S), the first par bigger than others; chaetotaxy of pro- and mesonotum as in Fig. 45 ; chaetotaxy of meso- and metanotum identical. Cervicosternum (Cr) triangular, divided completly by ecdysial longitudinal line with 6 setae and 2 pores ( Fig. 47 ). Prosternal area (Sn) with 2 small sternites, each with one seta; membranous surface with 10 setae: 6 anteriorly between Cr and Sn, 2 between sternites and 2 between coxal cavites (Cc). The area between pro- and mesothorax with a pair of functional spiracles ( Fig. 47 A).

Abdomen ( Figs 49 – 52, 54, 55 ): segments I–VIII each with tergite (Te) and sternite (St) divided into two parts by membranous area, a pair of paratergites (Pt) and a pair of parasternites (Ps) laterally ( Figs 49 – 51 ); partaergites of segment II – VIII divided into two parts: greater anterior and tiny posterior ( Fig. 51 ). Segment I: tergite with 34 setae (16/18) and a pair of sensilla (S) antero-lateraly ( Figs 49, 51, 51 C); sternite I with 20 (10/10) setae (6 micro) ( Fig. 50 ); each paratergite and parasternite of segment I with 5 setae and 3 setae, respectively ( Fig. 51 ). Segments II–VIII ( Figs 49, 50, 51 ): tergites with 45 (24/21) setae and a pair of sensilla (S) antero-lateraly ( Figs 49, 51 B); sternites with 32 (16/ 16) setae (10 micro) ( Figs 50, 51 ). Tergite and sternite of segment IX with 24 setae, macro setae mostly rod-shaped and frayed and 26 setae (some long setae rod-shaped and frayed), respectively ( Figs 52, 52 A, 54, 52). Segment IX with a pair of urogomphi, each one with two clearly visible segments ( Fig. 52 ): segment I slightly arched to inner side with 17 setae; segment II slightly arched to outer side with 3 setae (two micro, one long apically); tiny ring, which could be recognized as third segment between segment I and II ( Fig. 52 ); length ratio of segments I (with tiny ring), II of urogomphus and apical seta 2.7:1:1.5, respectively. Dorsal and ventral side of pygopod (segment X) with about 20 and about 35 setae, respectively ( Figs 52, 54, 55 ). Microstructure of urogomphi as in Fig. 52 C. Urogomphi (without seta apically) distinctly longer than pygopod; length ratio of segment I with tiny ring, II of urogomphi and pygopod 2.7:1:2.9. Microstructure of segments X as in Fig. 52 B. Abdominal segments I–VIII, each with a pair of spiracles (Sp) located between tergites and paratergites ( Figs 51 A, D).

Larval comparison between Platydracus species. The larval morphology of P. latebricola is presented for the first time. These new morphological data permit conducting intrageneric comparison. Mature larvae of P. latebricola (P.l) are very similar to the other known larvae of the genus — P. tomentosus (P.t) ( Schmidt 1994). The former species, a xerophile, occurs in Europe and Russi. The latter one, a ripicole, is known from the eastern North America ( Koch 1989; Brunke et al. 2011). Apart from the distribution, also larval characters (marked on figures by arrow: 1 – 3, 12, 19, 34, 38, 40, 47, 52) allow for distinguishing these species quite easily: 1) abdominal tergites and sternites: light, almost corouless – P.l; dark, brownish-grey – P.t; 2) micro setae on epicranial part of the head: numerous (about 100) – P.l, few (about 20) – P.t; 3) sides margins of the head: moderately rounded – P.l, parallel – P.t; 4) number of setae on apotome: 8 – P.l, 6 – P.t; 5) ligula: wide and short – P.l, narrow and longer – P.t; 6) segment I of urogomphi: as long as pygopod – P.l, twice longer to pygopod – P.t; 7) cervicosternum divided: completely – P.l, partially – P.t; 8) apical segments of maxillary and labial palp with 2 and 1, respectively: pores – P.l, tiny seta – P.t.

Figures

FIGURES 1 – 11. Mature larva of Platydracus latebricola (1 – 3, 7 – 11) and Staphylinus erythropterus (4 – 6). (1 – 6) General aspect of dorsal (1, 4), lateral (2, 5) and ventral view (3, 6); (7) simple macro setae of pronotum; (8, 9, 11) rod-shaped and frayed apically setae of abdominal tergite VII; (10) microseta of abdominal tergite VIII.

FIGURES 43 – 48. Mature larva of P. latebricola (43, 45, 47) and S. erythropterus (44, 46, 48). (43, 44) Fore leg with apical part of tibia (43 A, 44 A) and tarsungulus (43 B, 44 B) in anterior aspect; (45, 46) pronotum (I) and mesonotum (II) with microstructure of carina (45 A) in dorsal aspect; (47, 48) prothorax with structure of spiracle (47 A). Abbreviations: Cc—coxal cavity, Cr—cervicosternum, Fe—femur, S—sensillum, Sn—sternite, Tb—tibia, Tr—trochanter, Tu—tarsungulus.

FIGURES 49 – 55. Mature larva of P. latebricola (49 – 52, 54, 55) and S. erythropterus (53). (49) Abdominal tergites I and II with sensilla (S); (50) abdominal sternites I and II; (51) abdominal segments I and II with structure of spiracles in lateral aspect (51 A, D) and sensillia (51 B, C); (52, 53) abdominal segments IX and X with structure of lateral seta (52 A) and microstructure of segment IX (52 B) and urogomphus (52 C) in dorsal aspect; (54, 55) abdominal segments IX and X in lateral (54) and ventral (55) aspect. Abbreviations: Ug—urogomphus, Ps—parasternite, Pt—paratergite, S—sensillum, Sn—sternite, Sp—spiracle, Te—tergite.