Acrotelsella lauraensis, 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 : 20-27

Acrotelsella lauraensis sp. nov.

urn:lsid:zoobank.org:act:B5290CA5-7CB8-4C8E-9423-4D7B2AC2FDE3

Figs 55–78

Holotype ♀ (HW 1.19) QUEENSLAND: Laura , opposite school 15.5568°S 144.4470°E 97m asl, 16.vii.2013, Graeme Smith, bark spray to paperbark tree, QMT259421 (on two slides) . Paratypes (three males, two juveniles) 1♂ (HW 1.21) same data as holotype AMS K.541664 (on two slides, about to moult) ; 1♂ (HW 1.14) 2 juveniles (HW 0.91, 0.66) same data as holotype, AMS K.378006 (in alcohol) ; 1♂ (HW 1.08) Laura, opposite school 15.5568°S 144.4470°E 97m asl, 16.vii.2013, Graeme Smith, bark spray to ironbark tree, QMT259428 (on two slides); 2 juveniles (HW 0.63, 0.55) same data as previous, AMS K.378007 (in alcohol). Locality shown on the map in Figure 55 .

Diagnosis. This species can be distinguished from other described Acrotelsella with a simple ovipositor and trapezoidal thoracic sterna by a combination of characters including the darker scales on the antero-lateral margins of the nota when live, the presence of four papillae on the labial palp and from A. quattuor sp. nov. by the almost complete absence of pigment on the pedicel (versus moderate to strong on A. quattuor sp. nov.), the less distinct annulations of the terminal filaments (often absent) and the posterior margin of urosternite VIII in males is straight rather than slightly concave.

Description

Appearance: Medium silverfish with narrow body, thorax not much wider than the abdomen which only tapers slightly posteriorly. Scale pattern when live see Figure 56 , in alcohol mottled brown.

Body length: H+B up to 8.9 mm, HW 1.2 mm; thorax: length 2.6 mm or 0.28–0.33 H+B; width 1.9 mm with the mesonotum being slightly wider than the pronotum and metanotum. Antennae incomplete, maximum preserved length 6.0 mm or>0.67 H+B; terminal filaments incomplete, maximum length of terminal filaments 2.6 mm or>0.33 H+B.

Pigmentation: Brown to dark brown or almost black. Flagellum of antennae with distinct colour bands, the light areas on the holotype variable in length with some only one annulus long and others several annuli long; pedicel without patch of pigment on anterior face, scape without pigment. Frons without pigment around the eyes and among the macrochaetae anterior to the eyes, labrum and clypeus without pigment, mandibles with dark pigment over much of outer face, ultimate three articles of maxillary palp with rich brown pigment in basal half, second article with slight pigment in basal half; labial palp ultimate article with brown pigment along basal half of inner margin, penultimate article with very little pigment, just a little on the inner and outer margins. Nota and thoracic sterna without obvious pigment. Coxae of legs with a small amount of pigment in antero-lateral “shoulders” only. Trochanter with rich brown pigment distally on margin. Femora with dark brown/black pigment on the posterior margin beyond the bulge. Tibia with dark brown pigment patch on the distal dorsal face. First tarsal article with dark patch of pigment in distal half, remaining tarsomeres with only faint pigment. Abdominal segments without obvious pigment except for light pigment on coxites IX. Ovipositor largely without pigment except for a light scattering of pigment distally. Both pairs of abdominal styli with even brown pigment in basal ¾. Cerci and median filament with moderate brown pigment overall but quite variable with some specimens having distinct but small lighter bands at the apex of each division, others with only a hint of lighter colour on the distal most annulus.

Macrochaetae: Variable, straw coloured, many macrochaetae with quite slender delicate pectinations ( Figs 57–59 ) others with stronger pectinations especially distally.

Scales: Variable in shape with numerous sub-parallel ribs that do not surpass the margin of the scale ( Fig. 60 ) 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. 61 ) wider than long, with 1+1 open bushes of macrochaetae aligned in several, often ill-defined, 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 behind which is another row of macrochaetae three 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+(2–3) 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. 62 ) 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 many smaller setae on the dorsal face; first annulus/interval of flagellum with a ring of setae and a short trichobothrium; next six intervals with one ring of setae cilia and trichobothria; interval eight divided into two annuli each with a ring of setae, the distal ring also with cilia and a trichobothrium. In the most distal surviving intervals there are two very similar chains to each interval with a total of about 20 rings of chaetotaxy per interval as in Figure 63 . Type B and type C basiconic sensilla present. No circular sensilla observed. — 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. 64 ) with 2–4 setae 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 6–7 smooth apically bifurcate setae, galea a little longer than the lacinia with several small setulae or cilia over the surface and 4–5 larger setae basally; maxillary palp long and thin, apical article 4.2–4.5 times longer than wide and 1.0–1.1 times as long as the penultimate article which is distinctly shorter than the third and longest article, the ultimate article with a basiconic sensillum (type B); last two articles of palp with fine setae only, second and third article with scales and thin setae, some of these setae are a little stronger near the distal end of the article, first article with an incomplete subapical ring of slightly thicker setae. — Labium ( Fig. 65 ) very short and broad, postmentum with transverse row of strong simple setae, prementum very short with transverse and oblique rows of short stout simple setae, apically with curved setulae; labial palp with mostly fine setae although some stronger setae on second and third articles; apical article slightly expanded medio-distally, on average about as long as wide but large differences seen (L/ W 0.9 –1.3) with four papillae of compact type arranged in a single row (one side of QMT259428 with five papillae, the extra papilla appearing to be the result of a subdivision of the most laterad papilla), basiconic sensilla not seen on any of the three dissected specimens, surface covered with numerous fine setae.

Thorax: Pronotum ( Fig. 66 ) with setal collar only one macrochaetae wide, many macrochaetae only short with small pectinations but some more than twice as long as the others with strong pectinations in apical half; lateral margins with smaller and also longer finely pectinate setae along the margin, with eight combs of 1–3 strongly pectinate macrochaetae along each margin. Two open trichobothrial areas; the anterior trichobothrial area about 0.37–0.41 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 or between two macrochaetae; posterior trichobothrial area is located about 0.70–0.77 of the distance along the margin and is associated with the last comb which is composed of 1–2 macrochaetae with the short trichobothrium at the mediad end and a cilium at the laterad end, most combs associated 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 48% the total width of the pronotum. — Mesonotum ( Fig. 67 ) with lateral chaetotaxy similar to pronotum but with 10–11 combs each of 1–3 macrochaetae, the anterior trichobothrial area located 0.65–0.72 along the lateral margin associated with comb N-2 composed of one macrochaeta 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 (0.86–0.89), the trichobothrium located mediad to the comb of a single macrochaeta 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 long thin trichobothrium-like, with a few setulae between the comb and the margin. — Metanotum ( Fig. 68 ) similar to mesonotum with nine combs of 1–3 macrochaetae, the anterior trichobothrial area associated with comb N-1 of one macrochaeta about 0.73 along the margin, the posterior trichobothrial area associated with the most posterior comb (0.85–0.86 along margin) and the posterior 1+1 combs each of 4–6 macrochaetae the most lateral macrochaeta being long thin trichobothrium-like, with a few setulae between the comb and the margin.

Presternum with transverse row of small setae and setulae ( Fig. 69 ). — Prothoracic sternum ( Fig. 69 ) large and trapezoidal, 0.87–0.91 times as long as wide at its base, antero-lateral corners with several simple setae all on the margin, posterior ¾ of lateral margins with fringe of fine setae and some cilia as well as 4–5 combs each composed of 2–5 pectinate macrochaetae arranged in single straight or curved combs. — Mesosternum ( Fig. 70 ) trapezoidal, a little larger than prosternum (1.18–1.21 times as long) but similar in shape, about a long as wide at its base (L/ W 0.90 –0.94) 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 or 1+2 combs distally of 2–4 macrochaetae with additional slightly submarginal 1+1 strong setae nearer to the posterior end; all combs without associated setulae. — Metasternum ( Fig. 71 ) trapezoidal, shorter and wider than the mesosternum (L/ W 0.74 –0.79) with about two fine setae in the anterolateral corners, with long marginal setae and cilia only along margins adjacent to the combs; 1+1 subdistal combs of 4–6 pectinate macrochaetae.

Legs of average dimensions, neither long and slender nor short and stout, tibia L/W ratio of PI 1.8–2.5, PII 2.5–3.7, PIII 3.5–3.6; tarsi L/W ratio PI 6.3–7.3, PII 7.0–8.9, PIII 11.0–11.1. PI ( Fig. 69 ) with a row of about six macrochaetae laterally on the precoxa. Coxa with scales and a group of about nine macrochaetae on the anterolateral corners followed by a field of pectinate macrochaetae along the external margin about two macrochaetae wide; inner margin with four 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 occasionally 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 pectinate macrochaetae 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 two small setae distally mediad of the thick macrochaeta; dorsal margin with scales and two strong insertions; apex of tibia with a quite long apical spur which is strong (about half the length of the basal tarsal article) 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 a little stronger than the others. Pretarsus with two long curved lateral claws and a shorter curved medial empodium. PII ( Fig. 70 ) and PIII ( Fig. 71 ) similar to PI except the macrochaetae laterally on the coxae are somewhat reduced in the anterior half; legs progressively longer from PI to PIII and the relative length of the basal tarsal article is progressively longer being about 54% of the total length of the tarsus of PIII.

Abdomen: Urotergite I with 1+1 lateral combs of 5–6 macrochaetae, urotergites II–VII ( Fig. 72 ) with 3+3 combs of 2–10 macrochaetae as in Table 5, 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 ( Fig. 73 ) of female narrow triangular (39°) and acute but with the apex slightly withdrawn from the apex of a triangle, slightly wider at base than long (L/ W 0.69) with many delicately pectinate setae along entire margin both above and below, 5–6 combs on each side each composed of 1–6 macrochaetae usually with a cilium at the mediad end of each comb as well as a few setulae posterior to each comb. Urotergite X somewhat less acute in male (45–49°).

Urosternite I and II glabrous, urosternites III–VII with 1+1 lateral combs of 5–12 macrochaetae ( Fig. 74 ) each with a similar 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 5.5–20.5 times the average width of these combs, the ratio being largest on urosternite III and decreasing posteriorly.

Genital region of ♀ as in Figure 75 . Two pairs of styli, those on IX about one half or more times longer than those on VIII, with some robust setae apically. Coxites VIII with long combs of 10–11 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 ½ the width of the distal margin. Coxites IX with long rounded internal process about 4.6–4.8 times longer than wide at its base and 10.8–14.8 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 a few setae externally, inner process with strong smooth macrochaetae along the inner margins and long pectinate macrochaetae along the outer margin being dense on the basal third, many large scales in the distal half. — Ovipositor of primary type, quite long (2.17 HW), reaching to the apex of the long internal processes of coxites IX, with rows of fine setae on each article, both pairs of gonapophyses consisting of long basal division followed by smaller divisions that do not differ greatly in their length along the ovipositor, about 26 divisions in total.

Cerci ( Figs 76–77 ) with first division almost glabrous with just a couple of minute setae near the lateral margin, following three divisions wider than long with two rings of faintly pectinate setae, macrochaetae and trichobothria, following divisions progressively longer with two, then three, then four rings (eighth division) the basal and penultimate mostly just with trichobothria and scales; most distal surviving division (eleventh) of paratype K.541664 with eight rings of chaetotaxy but scales no longer visible.— Median dorsal appendage ( Fig. 76 ) first four divisions short with only a single ring of setae and trichobothria, fifth, six and seventh divisions with basal ring of scales and trichobothria and a subdistal ring of long finely pectinate or smooth setae, divisions 7–8 with four rings, the basal and third of scales and trichobothria, the second of setae cilia and trichobothria, the ultimate of macrochaetae and cilia. Epiproct and paraprocts quite darkly sclerotized or pigmented.

Coxite VIII in ♂ entire with 1+1 combs of 9–12 macrochaetae as well as many thin marginal setae and setulae between the comb and the margin; posterior margin between the combs straight. Coxites IX in ♂ separated ( Fig. 78 ) each side with a macrochaeta mediad of the base of the stylus. The internal process very acute apically about 3.2–3.9 times longer than the external process and 1.5–1.7 times as long as broad at its base. External and internal margins of internal process and external margin of outer process with many 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 collected by pyrethrum spray to the bark at the base of a paperbark tree and an ironbark tree.

Etymology. The species is named lauraensis referring to the only known locality in the town of Laura.

Figures

Figure 55. Known distribution of Acrotelsella lauraensis sp. nov.

Figure 56. Acrotelsella lauraensis sp.nov.from Laura,Queensland.

Figures 57–65. Acrotelsella lauraensis sp. nov. holotype ♀ (57) long pectinate macrochaeta of frons; (58) carrot-shaped macrochaeta of tibia of PI; (59) marginal macrochaeta of pronotum; (60) darker dorsal scale; (61) head (cross-hatched area obscured by eye pigment); (62) antenna, scape, pedicel and basal intervals of flagellum; (63) most distal surviving interval of flagellum; (64) maxilla; (65) labium. Scale bars = 0.1 mm.

Figures 66–69. Acrotelsella lauraensis sp. nov. holotype ♀ (66) pronotum, right half; (67) mesonotum, right side; (68) metanotum, right side; (69) presternum, prothoracic sternum and PI. Scale bars = 0.1 mm.

Figures 70–71. Acrotelsella lauraensis sp. nov. holotype ♀ (70) mesothoracic sternum and PII; (71) metathoracic sternum and PIII. Scale bars = 0.1 mm.

Figures 72–75. Acrotelsella lauraensis sp. nov. holotype ♀ (72) urotergite V, right side combs; (73) urotergite X; (74) right sublateral comb of urosternite VI; (75) coxites VIII and IX and ovipositor. Scale bars = 0.1 mm.

Figures 76–78. Acrotelsella lauraensis sp. nov. holotype ♀ unless otherwise indicated with specimen number (76) base of cerci and medial filament (broken off); (77) cercus, most distal surviving divisions, mid-length (K.541664); (78) coxite IX and stylus, left side with penis (K.541664). Scale bars = 0.1 mm.