Acrotelsella septentrionalis, 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 : 51-59

Acrotelsella septentrionalis sp. nov.

urn:lsid:zoobank.org:act:C3BAADD0-5C65-4A44-9987-78CD2D41432E

Figs 150–175

Holotype ♀ (HW 1.21) QUEENSLAND: Punsand Bay campground 10.7216°S 142.4599°E 5m asl, 23.vii.2013, Graeme Smith, eucalypt leaf litter, QMT259418 (on two slides). Paratypes (seven males, five females) 1♂ (HW 1.21) same data as holotype, QMT259425 (on two slides); 1♀ (HW 1.23) same data as previous, AMS K.541646 (on two slides); 2♀♀ (HW 1.28, 1.25) 1♂ (HW 1.16) same data as holotype, AMS K.377990 (in alcohol); 1♀ (HW 1.30) Pennefather campsite 12.2918°S 141.7033°E 7m asl, 19.vii.2013, Graeme Smith, paperbark leaf litter on sand, AMS K.541647 (two slides); 3♂♂ (HW 1.26, 1.20, 1.13) same data as previous, AMS K.377991 (in alcohol); 1♀ (HW 1.18) Heathlands Resources Reserve, along road to ranger station 11.7569°S 142.6709°E 152m asl, 21.vii.2013, Graeme Smith, leaf litter,AMS K.541649 (on two slides); 1♂ (HW 1.20) Jardine River NP, Jardine River South campsite 11.1399°S 142.3637°E 16m asl, 22.vii.2013, Graeme Smith, leaf litter in riverine forest ( Eucalyptus , Acacia or Melaleuca ), AMS K.541648 (on two slides); 1♂ (HW 1.15) same data as previous, AMS K.377992 (in alcohol). Localities shown on the map in Figure 150 .

Diagnosis. Distinguished from other described species of the group with secondary ovipositors by a combination of characters such as the presence of 7–10 papillae on the labial palp, the 3+3 arrangement of combs on the metasternum, 3–4 macrochaetae associated with the posterior trichobothria of the nota (versus two or three), and the normal width processes of coxites IX. It differs from A. mallee in having the anterior trichobothrial area of the pronotum more anterior (0.35–0.40 versus 0.43–0.49) associated with the comb N-3 rather than N-2, the gap between the posterior combs of the pronotum is 0.42–0.48 versus 0.50–0.54 the total width of the pronotum, it has a presternum with scales rather than numerous cilia and a large number of long pectinate carrot-shaped macrochaetae on the femora and tibia. In the males the posterior angle of urotergite X is more acute and similar to that of the female (60–65° versus 72–81°) and much less acute in the females of A. mallee .

Description

Appearance: Broad medium-sized silverfish with brown antennae, darker distally and light brown terminal filaments with rings of dark scales. When live ( Fig. 151 ) overall grey in colour with line of dark scales along posterior margin of head, all appendages dark. In alcohol, scales brown.

Body length: H+B up to 9.1 mm, HW 1.3 mm; thorax: length 2.6 mm or 0.27–0.31 H+B, width 2.35 mm with the mesonotum being slightly wider than the pronotum and not much wider than the metanotum. Antennae incomplete, maximum preserved length 5.8 mm or>0.7 H+B; terminal filaments all broken, maximum length of terminal filaments 4.0 mm or>0.5 H+B.

Pigmentation: Cuticle overall quite dark with specimens becoming very dark when they are placed into alcohol. The intensity of darkness makes it difficult to observe macrochaetae insertions in some places. Flagellum of antennae without banding, moderate brown pigment evenly distributed; pedicel and scape not particularly strongly pigmented. Frons without darker regions, labrum and clypeus without pigment, mandibles and maxillae without pigment among bushes of macrochaetae, maxillary and labial palps with brown pigment, the ultimate and penultimate articles of the maxillary palp moderately and evenly pigmented, other articles with some pigment distally. Ultimate article of labial palp with pigment around margins, other articles with very little pigment. Nota and thoracic sterna without obvious pigment. Some pigment on “shoulder” of the coxa of PI but not along the outer margin nor on PII or PIII. Trochanter sometimes with pigment along outer margin distally. Femora fairly evenly pigmented tending to darker distally and quite dark along the posterior margin distal of the posterior bulge. Tibia of all legs a little darker distally. First tarsal article with more pigment distally, remaining articles with some light pigment becoming stronger towards the claws. Outer margins of inner processes of coxites IX as well as outer process quite dark, penis moderately pigmented. Ovipositor evenly pigmented. Cerci and median filament evenly pigmented but appearing darkly annulated when live due to rings of dark scales. Abdominal styli light basally with a little darker pigment distally.

Macrochaetae: Variable strongly pectinate ( Figs 152–155 ) carrot-shaped and strongly pectinate or more subtly pectinate curved and tapered dark brown to hyaline, the pectinations extending almost along the whole length of the macrochaetae.

Scales: With numerous sub-parallel ribs that do not surpass the margin of the scale ( Fig. 156 ), those dorsal are brown to hyaline, those ventral brown or hyaline; the ribs are slightly further spaced on some irregular shaped hyaline scales. Scales found on frons and clypeus, on pedicel and scape, on second and third articles of maxillary palp, the submentum, all nota, all thoracic sterna, legs (except for trochanter and distal three articles of tarsi), all urotergites and urosternites, styli, medial filament and cerci. Scales of palps, styli, terminal filaments of variable shape, defined ribs clearly present on some scales but possibly not all.

Head: ( Fig. 157 ) wider than long with 1+1 not very dense bushes of macrochaetae aligned in subparallel rows on the antero-lateral corners, with a distinct gap in chaetotaxy between these two bushes. Eyes dark chestnut in alcohol preserved material. There is a small gap behind each bush in the row of macrochaetae along the margin of the frons which then extends inwards a little near a large but isolated peri-antennal group and its long thin trichobothrium-like seta; the marginal row continues back and up over the eyes about one macrochaeta wide. Clypeus with 1+1 very dense bushes of strongly pectinate macrochaetae as well as a few curved setae laterally, with only a single cilium on the face between the bushes. Labrum also with 1+1 bushes but with fewer pectinate macrochaetae as well as many simple setae scattered over the face and a single macrochaeta medially between the bushes. — Antennae fairly long, scape ( Fig. 158 ) not long with scales over much of its surface and a preapical ring of setae; pedicel with preapical ring of simple setae and cilia, with scales rather than setae over the face apart from an area with several tiny setulae; first annulus/interval of flagellum almost as long as the pedicel with a subapical ring of simple setae and trichobothria; next four annuli shorter but increasing in length each with ring of simple setae and one or two trichobothria; following two intervals similar but also with some long cilia; interval eight and nine each with two rings of chaetotaxy, the more basal of setae and cilia, the more distal also with a trichobothrium; intervals ten and eleven with three rings of chaetotaxy, the basal and distal rings as in the previous intervals the middle ring of setae only; interval twelve with four rings, the most basal now of setae only. The most distal surviving intervals ( Fig. 159 ) are divided into two chains each of five annuli with either a ring of setae only or a basal ring of setae only and a distal ring of cilia, the most distal ring of cilia in each interval also bears a trichobothrium. On most specimens examined as slide material both basiconic sensilla type B (rarely type C) and circular sensilla were seen. — Mandibles typical for Acrotelsella with well-developed molar and incisor areas; a group of about 12–15 strong apically bifurcated but simple setae distally adjacent to the pectinate molar area and a bush of around seventy strong, often dense pectinate macrochaetae externally as well as scattered simple setae. — Maxilla ( Fig. 160 ) with two or three thick slightly pectinate macrochaetae as well as a few small setae externally proximal to the palp, the lacinia with three strong teeth, one set further back than the other two, followed by about 6–7 lamellate processes and a row of 5–8 setae, galea longer than lacinia with about 3–6 smooth, simple setae externally in its basal half and several setulae distally; maxillary palp long, apical article 4.8–6.0 times longer than wide and 1.0–1.2 times as long as the penultimate article which is a little shorter than the antepenultimate article, the ultimate article with a small basiconic sensillum type B, last two articles of palp with fine setae only, third article with stronger setae in a subapical ring some slightly stronger setae subapically, second and third articles also with scales although these can be hard to find on the third article. — Labium ( Fig. 161 ) short and broad, postmentum with transverse row of mostly pointed setae, a couple laterally with blunt apices, prementum with transverse and oblique rows of strong apically truncate setae, apically with long curved setulae; labial palp short, apical article not expanded medially, about as long as wide (0.86–1.14) with row of 7–10 papillae of compact type arranged in a single curved row across most of the face margin, with a single very small rod-like basiconic sensillum (type B) on the outer margin, covered with numerous fine setae as well as longer fine setae.

Thorax: Pronotum ( Fig. 162 ) with dense setal collar of quite long but also shorter pectinate macrochaetae, about 2–3 macrochaetae wide without any medial gap; lateral margins with many strong, shorter and longer curved slightly pectinate macrochaetae as well as a few cilia, with 8–9 combs of 1–4 macrochaetae along each margin. Two open trichobothrial areas; the posterior trichobothrial area located about 0.69–0.75 of the distance along the margin and is associated with the last comb (N), this comb composed of 3–4 macrochaetae with the trichobothrium at the mediad end and a cilium at the laterad end, the anterior trichobothrial area is forward of the midpoint (0.35–0.40) and associated with comb N-3, the comb composed of only a single macrochaeta with the trichobothrium between the macrochaeta and the margin and a cilium laterad of the trichobothrium (sometimes a large marginal macrochaetae is positioned close to this trichobothrium giving the appearance of a macrochaeta being present on either side of the trichobothrium); all combs associated with a few setulae, sometimes more numerous. Posterior margin of all nota with 1+1 combs of 4–7 mostly pectinate macrochaetae associated with a few setulae between the comb and the margin and a cilium at each end, the most laterad insertion is probably occupied by a long thin trichobothrium-like macrochaeta (deduced from its shape); these combs not particularly widely spaced, the gap between them 42–48% of total width of pronotum. — Mesonotum ( Fig. 163 ) with lateral chaetotaxy similar to pronotum with 10–11 combs of 1–4 macrochaetae, the anterior trichobothrial area located 0.54–0.63 along the lateral margin, associated with comb N-2 (rarely N-3) composed of one macrochaeta with the trichobothrium located between the macrochaeta and the margin (occasionally a marginal macrochaeta laterad of trichobothrium) sometimes with a couple of setulae posterior to the comb and a cilium between the trichobothrium and the margin. Posterior trichobothrial area slightly more posterior than that on the pronotum (0.78–0.83) the trichobothrium located mediad to the comb of three or four macrochaetae and with 1–3 setulae or stronger setae posterior to the comb.— Metanotum ( Fig. 164 ) similar to mesonotum with 7–11 combs of 1–4 macrochaetae, the anterior trichobothrial area associated with comb N-1 of a single macrochaeta (or on one side of one specimen no macrochaeta) about 0.68–0.77 the distance along the margin, the trichobothrium located between the margin and the macrochaeta, the posterior trichobothrial area associated with the most posterior comb (0.83–0.88 along the margin) of 3–4 macrochaetae.

Presternum narrow, with transverse row of spaced pectinate macrochaetae ( Fig. 165 ) with scales between the row of macrochaetae and the prothoracic sternum not cilia. — Prothoracic sternum ( Fig. 165 ) parabolic, a little wider than long (L/ W 0.85 –0.96) antero-lateral corners with about 30 finely pectinate tapered marginal and submarginal setae, posterior three quarters of lateral margins with fringe of setae and some cilia as well as 5–9 short combs on each side each composed of 2–10 pectinate macrochaetae. — Mesosternum ( Fig. 167 ) only a little larger than prosternum (1.1–1.2 times as long) about as long as wide at its base (L/ W 0.95 –1.03) anterolateral corners glabrous, posterior third of margins with many long thin setae and 2–4 combs on each side distally, the more anterior composed of 5–8 pectinate macrochaetae in a single row and the more posterior composed of 4–8 pectinate macrochaetae; all combs with a few setulae behind them, larger smooth, tapered macrochaetae sometimes on the margin at the end of some combs. — Metasternum ( Fig. 168 ) of similar length to prosternum except wider (L/ W 0.74 –0.83) apically rounded with marginal setae and occasional cilia along distal 1 / 4 of lateral margins and 3+3 (occasionally four) combs of 2–9 pectinate macrochaetae.

Legs quite long, tibia L/W ratio of PI 2.2–2.6, PII 2.6–3.8, PIII 4.1–4.9; tarsi L/W ratio PI 6.8–8.2, PII range 7.7–9.9, PIII 11.3–14.7. PI ( Fig. 166 ) with a comb of 4–5 pectinate macrochaetae and one smooth macrochaeta laterally on the distal margin of the precoxa. Coxa with scales and a group of about 9–13 macrochaetae on the anterolateral corners usually arranged in two irregular rows followed by a field of strong pectinate macrochaetae along the external margin about three to four macrochaetae wide, the macrochaetae behind the margin pectinate and usually grouped into combs of 2–4; inner margin with six lightly pectinate tapering macrochaetae and several smooth and delicately pectinate setae of varying thickness distally over the articulation. Trochanter with setae only, some distally much stronger than those proximally as well as cilia and setulae. Femur posteriorly with some long thin pectinate macrochaetae as well as ten or more stout pectinate carrot-shaped macrochaetae along the posterior margin and a broken line of smooth setae posteriorly, dorsal margin with at least three strong curved pectinate macrochaetae over the articulation. Tibia of PI with about eight stout pectinate mostly carrot-shaped macrochaetae along the ventral margin as well as several longer thinner smooth setae, without row of shorter setae near the distal margin; dorsal margin with two short curved mildly pectinate macrochaetae spaced along the margin and a few smooth setae and long scales subdistally, with usual tibial spur bearing a few setae. Tarsi with four articles, the basal article of PI about half the total length of the tarsus, its join with the next article not oblique, the surface of all tarsal articles with numerous simple setae, those ventral near the distal end of the basal three articles more robust and with more rounded tips, especially on the two basal articles. Pretarsus with two long curved lateral claws and a shorter curved medial claw. PII ( Fig. 167 ) and PIII ( Fig. 168 ) similar to PI except the antero-lateral groups of macrochaetae on the coxa absent; legs progressively longer from PI to PIII (L tibia PI/PIII 0.43–0.55) and the relative length of the basal tarsal article is progressively longer, being about 0.6 of the total length on PIII.

Abdomen: Urotergite I with 1+1 lateral combs of 4–6 macrochaetae each associated with a cilium at both ends and 2–3 small marginal setae and several setulae between the comb and the margin, urotergites II–VII ( Fig. 169 ) with 3+3 combs of macrochaetae as in Table 11, the lateral combs with two cilia as well as 2–4 small marginal setae and several tiny setulae, the sublateral combs with a cilium at the mediad end as well as 1–3 small marginal setae and a few setulae, the submedial combs with a cilium at each end as well as 2–5 small marginal setae and several setulae; urotergite VIII with 2+2 combs (lacking the sublateral), also with a cilium at each end of both combs as well as a few marginal setae and several tiny setulae, urotergite IX glabrous. — Urotergite X ( Fig. 170 ) equilateral triangle (60–67°) in both sexes, wider at base than long (L/ W 0.62 –0.74) with many setae along entire margin and each side with 3–5 combs of 1–5 macrochaetae per comb (all lost) as well as a few setulae posterior to each comb, most combs with a cilium at the mediad end.

Urosternite I and II glabrous, urosternites III–VII with 1+1 lateral combs of 11–23 pectinate macrochaetae ( Fig. 171 ) each with a few marginal setae and several setulae between the comb and the margin as well as a cilium at the laterad end of each comb (occasionally not present). The distance between the lateral combs 2.1–4.6 times the average width of these combs, the ratio being largest on urosternite III or IV and decreasing posteriorly.

Genital region of ♀ as in Figure 172 . Two pairs of styli, those on IX with robust setae apically and along the length of the stylus, styli of VIII similar and not much smaller. Coxites VIII with long combs of 14–19 macrochaetae and a few small marginal setae and a few setulae in between the two, the coxites with straight truncate posterior margin and a slightly obtuse angle with the inner margin, the corner being moderately rounded with the curve occupying only ⅛ to ¼ the length of the posterior margin. Each coxite IX with long internal process which is quite broad about 2.3–2.6 times longer than wide at its base and 4.5–6.1 times longer than the short pointed external process, the inner processes reaching to about the apex of the ovipositor; outer process with stout setae along the outer margin, inner process with numerous, setae along the basal third of the outer margin adjacent to the stylus, a macrochaeta insertion mediad of the base of the stylus, the inner margin with 3–7 combs of 1–7 pectinate macrochaetae as well as some large marginal setae. — Ovipositor ( Figs 172–173 ) not very long (1.1–1.4 HW) of secondary type, only reaching the apex of the long internal processes of coxites IX, both pairs of gonapophyses consisting of longer basal divisions becoming progressively shorter distally except for the last divisions which are about as long as the previous two or three together, 12–14 divisions in total; the apical eight divisions armed with modified spines or conules which become more numerous distally, the last division with 6–10 modified spines; all divisions also with long fine setae.

Cerci ( Fig. 174 ) first division almost glabrous except for two small setae externally, second division with sub-basal semi ring of a few small setae and a distal ring of setae and some trichobothria, third division with a basal ring of setae and trichobothria, a medial ring of small trichobothria and small scales and a subdistal ring of some small finely pectinate setae and trichobothria, fourth division with a basal ring of scales and trichobothria and a subdistal ring of setae, cilia, trichobothria and externally a pectinate macrochaeta, fifth division with three rings, the basal and middle rings of scales and trichobothria, the subdistal also of setae, cilia, trichobothria and externally a pectinate macrochaeta, sixth division also with three rings but the basal ring also has some setae and the subdistal with larger macrochaetae externally, seventh and eighth divisions with four rings, the basal of scales and sometimes setae, the next of setae and long trichobothria, the following of scales and trichobothria and the subdistal as in previous divisions. — Median dorsal appendage ( Fig. 174 ), first division glabrous, the second with a basal ring of only a couple of long thin delicately pectinate setae near the outer margins and a subdistal ring of setae, following division with single subapical ring of setae, fourth division with three rings, the basal of setae and trichobothria, the next of setae trichobothria and scales, the subapical of setae and trichobothria, fifth division with only two rings the basal of scales and trichobothria, the subapical of setae, trichobothria and cilia, sixth and seventh divisions with three rings, the basal of setae trichobothria and scales, the middle of scales and trichobothria and the subapical as in the fifth division, eighth division with four rings, the basal of scales only, the second of scales setae and trichobothria, the third of scales and trichobothria and the subapical with setae, cilia and macrochaetae.

Male: Similar to female except urosternite VIII entire with posterior margin between the combs straight or very slightly concave. Coxites IX in ♂ separated ( Fig. 175 ) with internal process not very broad being only 1.5 times longer than wide at its base and 3.3–4.3 times longer than the short pointed external process, the inner processes not quite reaching to half the length of the stylus; outer process with stout setae along the outer margin, inner process with setae along both margins, as well as 4–5 submarginal combs of 1–5 macrochaetae along the inner margin, as well as a macrochaetae inserted mediad of the base of the stylus. Penis typical with numerous glandular setae apically, each set on a protuberance. Parameres absent.

Habitat. This species was always collected in dry leaf litter.

Etymology. The species is named septentrionalis from the Latin for northern, reflecting the current known distribution of the species at the northern most tip of the Cape York Peninsula.

Figures

Figure 150. Known distribution of Acrotelsella septentrionalis sp. nov.

Figure 151. Acrotelsella septentrionalis sp. nov. from Jardine River, Queensland.

Figures 152–161. Acrotelsellaseptentrionalis sp.nov.holotype ♀ (152) pectinate macrochaeta of clypeus; (153) long pectinate macrochaeta of pronotum; (154) shorter pectinate macrochaeta of pronotum; (155) carrot-shaped pectinate macrochaeta of femur of PII; (156) darker scale from pronotum; (157) head (cross-hatched area obscured by eye pigment); (158) antenna, scape, pedicel and basal intervals of flagellum; (159) idem, most distal surviving complete interval; (160) maxilla, arrow indicates basiconic sensillum; (161) labium, smaller chaetotaxy and papillae omitted from one palp. Scale bars = 0.1 mm.

Figures 162–166. Acrotelsella septentrionalis sp.nov.holotype ♀ (162) pronotum, left half; (163) mesonotum, left side; (164) metanotum, left side; (165) prothoracic presternum and sternum; (166) PI. Scale bars = 0.1 mm.

Figures 167–168. Acrotelsella septentrionalis sp. nov. holotype ♀ (167) mesothoracic sternum and PII; (168) metathoracic sternum and PIII. Scale bars = 0.1 mm.

Figures 169–173. Acrotelsella septentrionalis sp. nov. holotype ♀ (169) urotergite V, combs of left side; (170) urotergite X; (171) urosternite VI; (172) coxites VIII and IX with ovipositor; (173) apices of gonapophyses. Scale bars = 0.1 mm.

Figures 174–175. Acrotelsella septentrionalis sp. nov. paratype ♀ (K.541646)(174) base of left cercus and median filament, with epiproct and a paraproct; paratype ♂ (T259425); (175) urosternite VIII, coxites IX and penis. Scale bars = 0.1 mm.