Acrotelsella quattuor, Smith & Mitchell, 2024

Smith, Graeme B. & Mitchell, Andrew, 2024, On some silverfish taxa from the Cape York region of northern Australia (Zygentoma: Lepismatidae: Ctenolepismatinae), Records of the Australian Museum (Rec. Aust. Mus.) 76 (1), pp. 1-68 : 12-20

Acrotelsella quattuor sp. nov.

urn:lsid:zoobank.org:act:05BA4FBF-AF97-4B13-A819-05A87EC69972

Figs 30–54

Holotype ♀ (HW 1.23) QUEENSLAND: Oyala Thumatang NP, Mango Lagoon 13.6253°S 142.5758°E 82m asl, 30.vii.2013, Graeme & Louise Smith, bark spray to ironbark, QM T259420 (on two slides) . Paratypes (14 males, 11 females, eight juveniles) 1♀ (HW 1.16) same data as holotype, AMS K.541655 (on two slides) ; 1♂ (HW 1.13) same data as holotype, QM T259427 (on two slides) ; 1♂ (HW 0.90) same data as holotype, AMS K.377996 (in alcohol) ; 1♀ (HW 1.38) Oyala Thumatang NP, Mango Lagoon 13.6264°S 142.5780°E 76m asl, 31.vii.2013, Graeme & Louise Smith, bark spray to soft bark eucalypt, AMS K.541660 (on two slides) ; 1♀ (HW 1.26) same data as previous, AMS K.541661 (on two slides) ; 2♂♂ (HW 1.21, 0.93) same data as previous, AMS K.378002 (in alcohol) ; 1♂ (HW 1.13) Coen River campsite 13.9248°S 143.1922°E 221m asl, 16.vii.2013, Graeme Smith, bark spray to square bark tree, AMS K.541656 (on two slides) ; 1♀ (HW 1.23) same data as previous, AMS K.541657 (on two slides) ; 1♂ (HW 0.95) 1♀ (HW 1.10) 4 juveniles (HW 0.80, 0.74, 0.68, 0.58) same data as previous, AMS K.377997 (in alcohol) ; 1♂ (HW 1.35) Coen River campsite 13.9249°S 143.1921°E 227m asl, 16.vii.2013, Graeme Smith, bark spray, AMS K.377974 (in alcohol, about to moult) ; 3♂♂ (HW 1.08, 1.08, 1.01) same data as previous, AMS K.377999 (in alcohol) ; 1♀ (HW 1.14) same data as previous, AMS K.541658 (on two slides) ; 1♀ (HW 1.15) Archer River 13.4382°S 142.9428°E 52m asl, 17.vii.2013, Graeme Smith, bark spray to tree with lumpy bark, K.541659 (on two slides) ; 1♀ (HW 0.95) same data as previous, AMS K.377998 (in alcohol) ; 1♂ (HW 1.20) Oyala Thumatang NP, Mango Lagoon 13.6254°S 142.5757°E 75m asl, 30.vii.2013, Graeme & Louise Smith, bark spray to soft bark eucalypt, K.378000 (in alcohol) ; 2♂♂ (HW 1.13, 1.13) 1♀ (HW 1.00) 3 juveniles (HW 0.63, 0.63, 0.55) same data as previous, AMS K.378001 (in alcohol) ; 1♀ (HW 1.19) Oyala Thumatang NP, Chongs Swamp 13.6122°S 142.5822°E 73m asl, 31.vii.2013, Graeme & Louise Smith, bark spray to semi-rough bark tree, AMS K.541662 (on two slides) ; 1♀ (HW 1.40) QLD: Oyala Thumatang NP, Governor’s Waterhole 13.4385°S 142.3196°E 59m asl, 31.vii.2013, Graeme & Louise Smith, bark spray to soft bark eucalypt, AMS K.378003 (in alcohol) ; 1♀ (HW 1.20) 1♂ (HW 1.10) 1 juvenile (HW 0.68) same data as previous, AMS K.378004 (in alcohol). Localities shown on the map in Figure. 30 .

Not included in type series. 1♀ (HW 1.30) QUEENSLAND: Oyala Thumatang NP, Rockeby Rd ca 20km from Development Rd 13.6884°S 142.8996°E 192m asl, 1.viii.2013, Graeme Smith, bark spray to square barked eucalypt, AMS K.541663 (on two slides); 2 juveniles (HW 0.75, 0.58) same data as previous, AMS K.378005 (in alcohol) .

Diagnosis. This species belongs to the group of species with trapezoidal thoracic sternites; it can be distinguished by the presence of only four papillae on the ultimate article of the labial palp (versus three in A. auricoronata and five in A. marginata sp. nov.) and from Acrotelsella lauraensis which lacks the strongly pigmented pedicel of the antennae and distinctly annulated terminal filaments.

Description

Appearance: Medium to large silverfish, with narrow body, thorax slightly wider than the abdomen which only tapers slightly posteriorly. Scale pattern when live mottled grey ( Fig. 31 ), in alcohol mottled dark brown, almost black. Eyes dark chestnut, thorax and abdomen dorsally fairly evenly covered in brown scales. Terminal filaments distinctly annulated, the antennae also annulated but the lighter areas are small.

Body length: H+B up to 9.8 mm, HW 1.4 mm; thorax: length 3.0 mm or 0.26–0.34 H+B; width 2.3 mm with the mesonotum being slightly wider than the pronotum and metanotum, the metanotum being slightly shorter than the pro- and mesonota. Antennae incomplete, maximum preserved length 7.5 mm or>0.98 H+B; terminal filaments incomplete, maximum length of terminal filaments 7.6 mm or>0.99 H+B.

Pigmentation: Medium to dark brown. Flagellum of antennae with distinct annulations, the lighter areas small, restricted to the distal one or two annuli of each interval and not contrasting greatly with the darker annuli; pedicel with strong medial ring of darker pigment, scape with darker scales and pigment on ventral face. Frons with pigment around the eyes and among the macrochaetae anterior to the eyes, labrum, clypeus and mandibles without obvious pigment, distal two articles of maxillary palp with dark pigment in basal ⅔, antepenultimate article with patches of pigment along the sides; labial palp with strong pigment in basal half, penultimate article with pigment along the sides and the second article with some pigment distally. Pronotum with line of pigment along anterior edge of setal collar otherwise all nota and thoracic sterna without obvious pigment except for urotergite X which has distinct pigment either side at the base. Coxae of legs with distinct line of pigment along the external margin. Trochanter with darker pigment patch. Femora with pigment along posterior margin predominantly on the bulge and distal to it, with a little pigment on the dorsal distal margin. Tibia with patch of pigment in distal ⅓ but not extending to the apex; on PIII the pigment of the tibia extends along the whole dorsal margin. First tarsal article with pigment in medial ⅔, not extending to apices of the article, the remaining three tarsal articles with subtle pigmentation. Abdominal segments I– VIII without obvious pigment ventrally, coxites IX quite darkly pigmented (or sclerotised) especially around the stylus insertions. Ovipositor without pigment. Cerci and median filament distinctly annulated with the distal annulus in each division and the base of the first annulus lighter, the distal half of the first annulus with increasing pigment as is the penultimate article, all annuli between these quite darkly pigmented. Abdominal styli with pigment.

Macrochaetae: Variable, the majority of macrochaetae with quite slender delicate pectinations ( Figs 32–33 ), straw coloured.

Scales: Variable in shape, with numerous sub-parallel ribs that do not surpass the margin of the scale ( Fig. 34 ), those dorsal are brown, those ventral hyaline. Scales found on top of head, clypeus anterior to the bushes, on scape, on second and third articles of maxillary palp, on mentum of labium, all nota, all thoracic sterna, legs (except for trochanter and distal three articles of tarsi), all urotergites and urosternites, styli IX, medial filament and cerci.

Head: ( Fig. 35 ) wider than long, with 1+1 open bushes of macrochaetae aligned in several subparallel rows on the antero-lateral corners. Eyes dark brown in alcohol preserved material. The row of macrochaetae extends along the margin with a small gap above the antennal bases, beyond which is another line of macrochaetae two macrochaetae wide which extends to and above the eyes; the peri-antennal group is almost connected with the lateral rows. Clypeus with 1+1 very dense bushes of strongly pectinate macrochaetae as well as 2+2 macrochaetae between these bushes and the frons plus a few setae laterally. Labrum also with 1+1 bushes of pectinate macrochaetae as well as many small simple setae, some longer than others. — Antennae fairly long, scape ( Fig. 36 ) quite long with scales over surface and a preapical ring of numerous setae; pedicel with preapical ring of strong simple setae and cilia as well as smaller setae on the dorsal face as well as some small setulae scattered over face forming a circle; first annulus/interval of flagellum with two rings of setae and trichobothria, the sutures between the annuli/intervals very difficult to see in holotype; subsequent intervals with one or two rings of setae cilia and trichobothria. Based on the presence of trichobothria in the ultimate ring of each interval, the intervals clearly consist of two rings by the seventh interval and four by the tenth. In the most distal surviving intervals there are two very similar chains to each interval with a total of about eight rings of chaetotaxy per chain as in Figure 37 . Type B basiconic sensilla present but not abundant and possibly type C basiconic sensilla or Silvestri-type sensilla. — Mandibles typical for Acrotelsella with prominent molar and large incisor areas; a group of about eleven strong apically bifurcated but simple setae distally adjacent to the pectinate molar area and a bush of about 100 pectinate macrochaetae externally as well as scattered simple setae. — Maxilla ( Fig. 38 ) with one large and one smaller seta externally proximal to the palp, the lacinia with three strong teeth, one set further back than the other two, followed by seven lamellate processes and a row of seven smooth apically bifurcate setae; galea almost as long as the lacinia with several small setulae or cilia over the surface and four or five larger setae basally; maxillary palp long and thin, apical article 4.3–5.7 times longer than wide and 0.93–1.16 times as long as the penultimate article which is a little shorter than the third and longest article, the ultimate article with basiconic sensilla type B; last two articles of palp with fine setae only, second and third article with scales and thin setae, some of which are a little stronger near the distal end of the article, first article with an incomplete subapical ring of slightly thicker setae. — Labium ( Fig. 39 ) short and broad, postmentum with transverse row of strong mostly simple setae, prementum with transverse and oblique rows of short strong mostly simple setae, apically with curved setulae; second article of labial palp with a few strong setae medially; apical article quite variable in shape, usually expanded medially, on average about as long as wide but large differences seen (L/ W 0.89 –1.33) with four papillae of compact type arranged in a single row, with a small stout basiconic sensillum near the outer margin at the level of the papillae, surface covered with numerous fine setae.

Thorax: Pronotum ( Fig. 40 ) with setal collar about two macrochaetae wide; lateral margins with smaller but stout finely pectinate setae along the margin, with 7–9 combs of 1–3 strongly pectinate macrochaetae along each margin. Two open trichobothrial areas; the anterior trichobothrial area about 0.38–0.44 of the distance along the margin, associated with comb N-3, the trichobothrium being placed between the single macrochaeta of the comb and the margin on the holotype and a few other specimens but almost as many have the trichobothrium located between two macrochaetae; posterior trichobothrial area is located about 0.75–0.81 of the distance along the margin and is associated with the last comb which is composed of one or two macrochaetae with the short trichobothrium at the mediad end and a cilium at the laterad end, most combs with 1–3 setulae posterior to the comb. Posterior margin with 1+1 combs of 4–6 insertion points, each associated with a few small setae between the comb and the margin and a cilium at each end; the outermost insertion on the comb is occupied by a long thin trichobothrium-like seta. The distance between the lateral combs of the pronotum 43–48% the total width of the pronotum. — Mesonotum ( Fig. 41 ) with lateral chaetotaxy similar to pronotum but with 9–11 combs each of 1–4 macrochaetae, the anterior trichobothrial area located 0.62–0.70 along the lateral margin associated with comb N-2 composed of one macrochaeta (rarely two) with the trichobothrium located between the macrochaeta and the margin, with a few setulae posterior to the comb and a cilium at the mediad end. Posterior trichobothrial area slightly more posterior than that on the pronotum (0.84–0.89), the trichobothrium located mediad to the comb of 1–2 macrochaetae and with a few setulae posterior to the comb. Posterior margin with 1+1 combs of 4–6 macrochaetae insertions usually with a cilium at each end, the most lateral macrochaeta most likely a long, thin, trichobothrium-like, with a few setulae between the comb and the margin. — Metanotum ( Fig. 42 ) similar to mesonotum with 8–10 combs of 1–4 macrochaetae, the anterior trichobothrial area associated with comb N-1 (rarely N-2 on one side only) of one macrochaeta (rarely two) about 0.67–0.77 along the margin, the posterior trichobothrial area associated with the most posterior comb (0.85–0.89 along margin) and the posterior 1+1 combs each of 4–6 macrochaetae the most lateral macrochaeta being a long thin, trichobothrium-like, with a few setulae between the comb and the margin.

Presternum with transverse row of small setae and setulae ( Fig. 43 ). — Prothoracic sternum ( Fig. 43 ) large and trapezoidal, 0.91–1.08 times as long as wide at its base, antero-lateral corners with several simple setae all on the margin, posterior ⅔ of lateral margins with fringe of fine setae and some cilia as well as 4–8 combs each composed of 1–5 pectinate macrochaetae arranged in single straight or curved combs. — Mesosternum ( Fig. 44 ) trapezoidal, a little larger than prosternum (1.11–1.19 times as long) but similar in shape, almost as long as wide at its base (L/ W 0.90 –0.98), with a few fine setae in the anterolateral corners, with long thin simple marginal setae and cilia at the posterior corners, not extending much beyond the combs and 2+2 combs (rarely 1+2) distally of 2–5 macrochaetae with additional slightly submarginal 1+1 strong setae nearer to the posterior end; all combs without associated setulae. — Metasternum ( Fig. 45 ) trapezoidal, shorter and wider than the mesosternum (L/ W 0.70 –0.76) with a few fine setae in the anterolateral corners, with marginal setae and cilia only along margins adjacent to the combs; with 1+1 or more rarely 1+2 subdistal combs of 2–6 pectinate macrochaetae.

Legs of average dimensions, neither long and slender nor short and stout, tibia L/W ratio of PI 2.2–3.2, PII 2.4–3.4, PIII 3.2–4.2; tarsi L/W ratio PI 5.9–9.1, PII 7.2–9.6, PIII 7.5–10.1. PI ( Fig. 43 ) with a row of about six macrochaetae laterally on the precoxa. Coxa with scales and a group of about eight macrochaetae on the anterolateral corners followed by a field of pectinate macrochaetae along the external margin about 2–3 macrochaetae wide; inner margin with four lightly pectinate tapered macrochaetae and several shorter smooth and pectinate setae of varying thickness distally over the articulation; distal end with distinct cleft, with a row of small setae along the mediad margin. Trochanter with one small pectinate macrochaeta and a few fine setae. Femur posteriorly with some slender pectinate macrochaetae, in addition to some stronger tapered and carrot-shaped macrochaetae along the margin to the posterior bulge then a row of about seven setae along the margin to the articulation; anterior margin with a strong macrochaeta about ⅔ along the margin and three strong insertions near the articulation. Tibia of PI with a very strong stout pectinate carrot-shaped macrochaeta near the distal end and some thin pectinate setae and smaller smooth setae along the posterior margin and just two small insertions distally mediad of the thick macrochaeta; dorsal margin with scales and five strong insertions; apex of tibia with the usual apical spur which is stout and covered in numerous setae. Tarsi with four articles, the basal article of PI a little less than half the total length of the tarsus, its join with the next article not oblique, whereas the distal margin of the second article is quite oblique, the surface of all tarsal articles with very numerous simple setae, those distally and below stronger than the others. Pretarsus with two long curved lateral claws and a shorter curved medial claw. PII ( Fig. 44 ) and PIII ( Fig. 46 ) similar to PI except the macrochaetae laterally on the coxae are somewhat reduced in the anterior half on PII and much reduced in the anterior half on PIII; the tibia of PIII has a long thin trichobothrium-like seta about ¼ the distance along the outer margin; legs progressively longer from PI to PIII and the relative length of the basal tarsal article is progressively longer, being about 55% of the total length of the tarsus of PIII.

Abdomen: Urotergite I with 1+1 lateral combs of 4–6 macrochaetae, urotergites II–VII ( Fig. 47 ) with 3+3 combs of 3–11 macrochaetae as in Table 4, urotergite VIII with 2+2 combs (lacking the sublateral), urotergite IX glabrous; the lateral and submedial combs with a cilium at each end and the sublateral with a cilium only at the mediad end; all combs with several small setae and setulae between the comb and the margin. — Urotergite X ( Figs 48–49 ) of female narrow triangular (35–50° in both sexes) and acute but with the apex slightly withdrawn from the apex of a triangle in some specimens, slightly wider at base than long (L/ W 0.87 –0.97) with many delicately pectinate setae along entire margin inserted both above and below, 6–7 combs on each side, the combs composed of 2–6 macrochaetae per comb usually with a cilium at the mediad end of each comb, as well as a few setulae posterior to each comb.

Urosternite I and II glabrous, urosternites III–VII with 1+1 lateral combs of up to 14 pectinate macrochaetae ( Fig. 50 ) each with a smaller number of setulae between the comb and the margin as well as a cilium at the lateral end of every comb. The distance between the lateral combs 4.4–20.2 times the average width of these combs, the ratio being largest on urosternite III and decreasing posteriorly.

Genital region of ♀ as in Figure 51 . Two pairs of styli, those on IX about one third longer than those on VIII, each with some robust setae apically. Coxites VIII with long combs of 9–14 macrochaetae and a smaller number of thin setae and setulae between the comb and the margin, the coxites with rounded inner corners, the straight section being about ⅓–½ the width of the distal margin. Coxites IX with a long rounded internal process about 4.7–6.3 times longer than wide at its base (longer in larger specimens) and 7.9–11.6 times longer than the short pointed external process, the inner processes surpassing the apex of styli IX including macrochaetae, almost reaching to the end of the ovipositor; outer process with several setae externally, inner process with strong smooth macrochaetae along the margins, being very dense on the outer margin where many large scales also exist. — Ovipositor of primary type with rows of fine setae on each article, quite long (1.65–2.33 HW) reaching to the apex of the long internal processes of coxites IX, both pairs of gonapophyses consisting of long basal division followed by smaller divisions that do not differ greatly in their length along the ovipositor, 24–27 divisions in total.

Cerci ( Figs 52–53 ) with first division almost glabrous with just a couple of minute setae near the lateral margin, following three divisions wider than long with two or three rings of faintly pectinate setae macrochaetae and trichobothria, the middle ring composed mostly of scales, following divisions progressively longer with four rings per division by the sixth division, the basal and third rings mostly of scales and sometimes a cilium, the second ring of setae cilia and trichobothria, the most distal also with long distinctly pectinate macrochaetae; most distal surviving division in holotype (fourteenth) with eight rings of chaetotaxy but scales no longer visible.— Median dorsal appendage ( Fig. 54 ) first four divisions short with only a single ring of setae although some isolated scales suggest scales may be present distal of the ring, fifth and sixth divisions with basal ring of scales and trichobothria and a subdistal ring of long, finely pectinate or smooth setae, divisions 7–9 with four rings, the basal and third of scales and trichobothria, the second of setae and trichobothria, the ultimate of macrochaetae and cilia. Epiproct and paraprocts quite darkly sclerotized or pigmented.

Urosternite VIII in ♂ entire with 1+1 combs of 9–14 macrochaetae as well as many thin marginal setae and setulae between the comb and the margin; posterior margin between the combs concave. Coxites IX in ♂ separated ( Fig. 54 ) each side with a long smooth macrochaeta mediad to the base of the stylus. The internal process very acute apically, about 2.9–5.3 times longer than the external process and 1.3–1.6 times as long as broad at its base. External and internal margins of internal process and external margin of outer process with many smooth or perhaps very finely pectinate setae and macrochaetae. Outer process small triangular with several stout finely pectinate setae along the outer margin. Penis typical with numerous glandular setae apically each set on a protuberance. Parameres absent.

Habitat. This species was always collected from the bark of a variety of trees using the bark spray methodology. Localities as in Figure 30 .

Etymology. This species is named Acrotelsella quattuor from the Latin number for four, referring to the number of papillae on the ultimate article of each labial palp.

Remarks. The specimens from Rockeby Road have not been included in the type series because we do not have supporting molecular data, the ovipositor is shorter with fewer divisions and the location of the anterior trichobothrial area of pronotum is at the anterior end of the range but otherwise these specimens conform with Acrotelsella quattuor sp. nov.

Figures

Figure 30. Known distribution of Acrotelsella quattuor sp. nov.

Figure 31. Acrotelsella quattuor sp. nov. from Mango Lagoon in Oyala Thumatang NP, Queensland.

Figures 32–39. Acrotelsella quattuor sp. nov. holotype ♀ (32) pectinate macrochaeta of clypeus; (33) long pectinate macrochaeta of pronotum; (34) darker scale from pronotum; (35) head (cross-hatched area obscured by eye pigment); (36) antenna, scape, pedicel and basal intervals of flagellum; (37) idem, most distal surviving complete interval; (38) maxilla; (39) labium, smaller chaetotaxy and papillae omitted from one palp. Scale bars = 0.1 mm.

Figures 40–43. Acrotelsella quattuor sp. nov. holotype ♀ (40) pronotum, right side; (41) mesonotum, right side; (42) metanotum, right side; (43) prothoracic presternum, sternum and PI. Scale bars = 0.1 mm.

Figures 44–46. Acrotelsella quattuor sp. nov. holotype ♀ (44) mesothoracic sternum and PII; (45) metathoracic sternum; (46) PIII. Scale bars = 0.1 mm.

Figures 47–53. Acrotelsella quattuor sp. nov. holotype ♀ unless otherwise indicated by specimen number (47) urotergite IV, right side; (48) urotergite X; (49) urotergite X of ♂ (T259427); (50) urosternite VII; (51) coxites VIII and IX with ovipositor; (52) base of left cercus and median filament, with epiproct and a paraproct; (53) most distal surviving division of cercus with pigment density shown. Scale bars = 0.1 mm.

Figure 54. Acrotelsella quattuor sp. nov. paratype ♂ (T259427), posterior margin of urosternite VIII, coxites IX and penis. Scale bars = 0.1 mm.