Heterolepisma howense Womersley

Smith, Graeme B. & Mitchell, Andrew, 2019, Species of Heterolepismatinae (Zygentoma: Lepismatidae) Found on some Remote Eastern Australian Islands, Records of the Australian Museum 71 (4), pp. 139-181 : 143-151

Heterolepisma howense Womersley

Heterolepisma howensis Womersley, 1942:116 .

Figs 4–41

Holotype. ♂ ( HW 1.28 ) (K. 263961 in alcohol) LORD HOWE ISLAND: Rocky Run, 31.55°S 159.09°E, iv.1942, Max Nicholls . Paratypes. 5♂♂ 8♀♀ 12 partial specimens and some fragments including allotype ♀ ( HW 1.38 ) (K. 263962 in alcohol) same data as holotype ; 1♀ ( HW 1.25 ) (K.541009 K.541010 on two slides) same data as holotype ; 1♀ ( HW?) (K.261040 K.261041 on two slides) same data as holotype ; 1♀ ( HW 1.23 ) (K.261311 on slide) same data as holotype ; 1♂ ( HW??) (K.261038, K.261039 on two slides) same data as holotype ; 1 partial specimen ( HW 1.30 ) (K. 263963 in alcohol), same data as holotype (head, thorax and abdomen I–IV only) ; 1♀ ( HW 1.21 ) (K. 377841 in alcohol) same data as holotype ; 1 partial specimen ( HW 1.23 ) (K. 377842 in alcohol) same data as holotype (head, thorax and abdominal segments I–III only) ; 1♂ ( HW 1.10 ) (K. 377843 in alcohol) same data as holotype ; 1♀ ( HW 1.25 ) (K. 377844 in alcohol) same data as holotype ; 1 partial specimen ( HW 1.23 ) (K. 377845 in alcohol) same data as holotype (head, thorax and abdominal segments I–IV only) ; 1♂ ( HW 0.90) (K. 377846 in alcohol) same data as holotype ; 1♀ ( HW 1.08 ) (K. 377847 in alcohol) same data as holotype ; 1♂ ( HW 1.00) (K. 377848 in alcohol) same data as holotype ; 1 partial specimen ( HW 1.00) (K. 377849 in alcohol) same data as holotype (head, thorax and abdominal segments I–III only) ; 1♀ ( HW 1.13 ) (K. 377850 in alcohol) same data as holotype ; 1 partial specimen ( HW 1.18 ) (K. 377851 in alcohol) same data as holotype (head, thorax and abdominal segments I–III only) ; 1 partial specimen ( HW 1.08 ) (K. 377852 in alcohol) same data as holotype (head, thorax and abdominal segments I–V only) ; 1 partial specimen ( HW 1.15 ) (K. 377853 in alcohol) same data as holotype (head, thorax and abdominal segments I–IV only) ; 1♂ ( HW 1.18 ) (K. 377854 in alcohol) same data as holotype ; 1 partial specimen ( HW?) (K. 377855 in alcohol) same data as holotype (thorax and abdominal segments I–VI only) ; 1 partial specimen ( HW 1.00) (K. 377856 in alcohol) same data as holotype (head, thorax and abdominal segments I–III only) ; 1 partial specimen ( HW 1.04 ) (K. 377857 in alcohol) same data as holotype (head, thorax and abdominal segments I–III only) ; 1 partial specimen ( HW 1.03 ) (K. 377858 in alcohol) same data as holotype (head, thorax and abdominal segments I–IV only) ; 1 juvenile ♀ ( HW 0.83) (K. 377859 in alcohol) same data as holotype ; 1 partial specimen ( HW 0.93) (K. 377860 in alcohol) same data as holotype (head, thorax and abdominal segments I–III only) ; fragments (K. 377861 in alcohol) same data as holotype .

Additional Lord Howe Island material examined. 1♂ ( HW 1.20 ) (K.541011 K.541012 on two slides) LORD HOWE ISLAND : Goat House walking track, 350m from start, Intermediate Hill 31.554°S 159.080°E, 8.xii.2000, G. Cassis, LHI/ GC / L 12 d; 1♂ ( HW 0.95) (K. 377862 in alcohol) same data as previous (in two pieces) ; 1 juvenile ( HW 0.68) (K. 377865 in alcohol) LORD HOWE ISLAND : Point where walking trail first enters Erskine Valley from coast 31.574°S 159.072°E, 28.xi.2000, LHIS043 /04B.

Non Lord Howe Island material examined. 1♂ ( HW 1.11 ) (K.261293 K.261294 on two slides) NORFOLK ISLAND: Birdrock track, National Park , 29.01°S 167.94°E, 26.x.2013, A. Wells, L. Mound LAM5845 ; 1 juvenile ( HW 0.59) (K. 377824 in alcohol) same data as previous ; 1♀ ( HW 1.13 ) (K. 377825 in alcohol) NORFOLK ISLAND (not further specified), 22–29.x.1967, C. N. Smithers ; 1♂ ( HW 0.95) (K.261290 K.261291 on two slides) same data as previous ; 1♂ ( HW 0.93) (K. 377826 in alcohol) same data as previous ; 1 damaged ♀ (most of head and pronotum broken off) (K.261292 on one slide) same data as previous .

Diagnosis. This species can easily be distinguished from other described species of Heterolepisma with a glabrous anterior margin on the frons, a glabrous urosternite I, 1+1 single macrochaetae on urosternites II–VII, three pairs of styli in the female and two in the male (i.e. H. cooloola Smith et al., 2019 , and also possibly the inadequately described H. kraepelini Silvestri, 1908 ) by its trapezoidal urotergite X, by the absence of a macrochaeta mediad of the anterior trichobothrium of the pronotum, by the absence of combs of two macrochaetae on the meso- and metanota, by the absence of a smaller secondary macrochaeta in the posterior combs of the nota and urotergites.

Redescription

Appearance: Medium sized silverfish, thorax about 15% wider than abdomen which only tapers slightly posteriorly from about the fifth abdominal segment; appearance when live unknown.

Body length: Maximum H+B 8.4 mm; HW 1.38 mm; thorax: length 2.7 mm or 0.33 H+B (range 0.30–0.39); width up to 2.1 mm with no great difference in length or width between the pro, meso- and metanota although the pronotum is the narrowest; most antennae lost, maximum preserved 0.7 H+B (about 0.5 H+B in the original description); terminal filaments also mostly lost (0.8 H+B in original description).

Pigmentation: Pigment completely faded in all type material; the following description of pigmentation was made using specimen K.541011 before it was dissected. Pigment pinkish/ brown but can vary considerably between specimens. Flagellum of antennae evenly pale becoming slightly darker distally; pedicel and scape without pigment. Scape with pinkish pigment on external face. Terminal filaments annulated darker brown with the most distal annulus of each major division completely lacking pigment. Head with pigment around eyes and along sides of head to the antennae and among the peri-antennal macrochaetae. Clypeus, labrum and mandibles without pigment. Maxillary palp with light pink pigment along sides of ultimate article and similar but darker pigment on the penultimate article, less on the third article and very little on the first two articles. Labial palp largely without pigment. Legs with slight pigment on anterior “shoulder” of coxae, absent from trochanter, slight pigment on the posterior bulge and distal dorsal apex of femur, tibia with light pigment which is slightly stronger proximally and somewhat stronger again distally near dorsal margin, darkish pigment on first tarsal article only. Urotergite X with pigment in basal lateral region.

Macrochaetae: Smooth, hyaline or slightly straw coloured, apically bifurcate with truncated tips to each bifurcation. Some macrochaetae on tibia, stout carrot-shaped.

Scales: Quite broad, hyaline or with brown ribs, with numerous subparallel ribs that do not surpass the margin of the scale ( Fig. 4 ). Scales found on top of head, protruding well forward over the margin in the medial region; round scales absent from clypeus and labrum as well as from all cephalic appendages and styli; present on all nota, all thoracic sterna, and coxae of legs but absent from remaining leg articles, present on all urotergites and urosternites. Lanceolate scales ( Fig. 5 ) present on clypeus, femora, tibia, basal divisions of cerci and probably also on scape.

Head: Wider than long ( Fig. 6 ), without distinct bushes. Anterior margin of frons glabrous with small medial indented region, lateral margins anteriorly with a single row of strong macrochaetae which becomes about two macrochaetae wide near the anterior margin of the antenna; peri-antennal groups of three larger macrochaetae and several small setae or cilia; the marginal rows continue back to the level of the eyes and a single row of strong macrochaetae extend back above the eyes. Clypeus with numerous setae and cilia, the setae being longer and stronger in the proximal lateral parts, where lanceolate scales also occur. Labrum with several setae scattered over the proximal third and a row of six fine setae medially near the distal margin. — Antennae with scape much longer than pedicel ( Fig. 7 ), scape with a subapical rosette of strong setae, the sides and ventral face with numerous smaller setae and probably some lanceolate scales; pedicel also with subapical rosette of strong setae but also several cilia and small setae in a row proximal to the larger setae. First annulus of flagellum with a subapical ring of setae and some short trichobothria; subsequent annuli similar but becoming slightly longer, dividing into two annuli by the eighth interval and into four annuli by the about the twelfth interval. Most distal surviving intervals of almost complete antenna ( Fig. 8 ) divided into repeated patterns of eight annuli, each with two rosettes of fine setae; rod-like basiconic sensilla (Type B of Adel, 1984) present distally in the distal annulus of each interval. — Mandibles ( Figs 9, 10 ) typical for Heterolepismatinae with well- developed molar and incisor areas; a group of about 9–12 strong and short or thin and longer, apically bifurcated setae distally adjacent to the molar region and a bush of about 40 macrochaetae externally. — Maxilla ( Fig. 11 ) with two thick apically bifurcate macrochaetae externally proximal to the palp; lacinia typical for genus, with three strong teeth, one set further back than the other two, followed by about seven lamellate processes and a row of eight or nine thin setae, galea with one slightly stronger seta proximally but otherwise with only short fine cilia or setulae ( Fig. 12 ); apical article of maxillary palp ( Fig. 13 ) 4.1 times longer than wide (range 3.7–4.6) and 1.2 times longer than the penultimate article (range 1.1–1.4), the ultimate article apparently with three (or four on K.541011) branched papillae, ultimate and penultimate articles with fine setae only, third article with subapical rosette of somewhat stronger setae one of which is quite strong, second article with subapical rosette of stronger setae as well as several somewhat stronger setae on the ventral face, basal articles with rosette of short thicker setae. — Labium ( Fig. 14 ) wider than long, postmentum with setae scattered irregularly across the anterior third and a group of setae in the posterior corners, three or four of which may be quite robust, prementum with transverse and oblique groups of stronger setae and with short setulae distally; apical article of labial palp almost as wide as long (L/ W 0.8 –1.1) with five compact papillae of similar size arranged in a broad three plus two arrangement, outer margin with one basiconic sensillum (type C) and at least one basiconic sensillum (type B); covered with numerous fine short setae, those proximal and medial longer than those distal and/or lateral; penultimate article without particularly stronger setae.

Thorax: Pronotum ( Fig. 15 ) with setal collar of short macrochaetae, some small setulae and longer cilia; macrochaetae and setae of lateral margins of Lord Howe Island specimens lost, but the specimen from Norfolk Island (K. 261293, K. 261294) (see below) has several quite long macrochaetae along the margins of all nota, as well as setulae and long cilia; all macrochaetae are single. Anterior trichobothrium about half way along the margin and not associated with any macrochaeta ( Fig. 16 ). The posterior trichobothrium mediad of a large submarginal macrochaeta ( Fig. 17 ). Both trichobothria with two or three setulae posterior to them. Posterior margin with 1+1 single macrochaetae each associated with two cilia ( Fig. 18 ). — Mesonotum ( Figs 19, 20 ) with similar lateral chaetotaxy to pronotum except there are many more setulae along the margins; the anterior trichobothrial area not associated with any macrochaetae and about ¾ the distance along the margin, the posterior area as in the pronotum; 1+1 posterior macrochaetae as in pronotum. — Metanotum ( Figs 21, 22 ) similar to mesonotum (the macrochaeta is missing from the right posterior trichobothrial area of K.541011 but present on all other specimens).

Presternum narrow, with transverse row of strong macrochaetae, setae and cilia ( Fig. 23 ). All thoracic sterna with hyaline scales. — Prothoracic sternum ( Fig. 23 ) parabolic, about as long as wide at its base (L/W = 0.99, range 0.85–1.10), posterior one third of lateral margins with marginal setae, 1+1 submarginal combs each of three or four macrochaetae; apex between the combs straight and glabrous with scales extending beyond the margin. — Mesosternum ( Figs 24 ) a little longer than wide (L/ W 1.07, range 1.04–1.11), similar to prosternum with straight or slightly concave distal glabrous region between the setae, with 1+1 submarginal combs of about five macrochaetae as well as some strong marginal setae, some cilia and one or two setulae along the posterior fifth of the margin. — Metasternum ( Fig. 25 ) apically rounded, much wider than long (L/ W 0.72, range 0.69–0.75), with submarginal rows of four or five macrochaetae as well as some marginal setae (some of which are quite robust) and cilia in the posterolateral corners; the gap between the combs about six times the average length of each comb (range 4.7–7.8).

Legs ( Figs 23–25 ) becoming progressively longer and more slender (length tibia PII/PI 1.10–1.34; tibia PIII/PI 1.56–1.98), tibia L/W ratio of legs PI 3.0 (range 2.5–3.6), PII 3.5, (range 3.1–4.5), PIII 4.4 (range 3.3–5.3); tarsi L/W ratio PI 6.0 (range 5.2–6.6), PII 7.9 (range 6.9–8.9), PIII 10.1 (range 8.9–11.3). Precoxa of PI with lateral comb of three strong macrochaetae. Coxa of PI with strong macrochaetae in about two rows along the external margin; inner margin with about five stout macrochaetae distally over the articulation and another two strong longer setae subdistally near long thin setae on the dorsal face. Trochanter with several fine setae as well as one stronger seta. Femur ventrally with several macrochaetae along the posterior margin and another about two thirds the distance along the anterior margin, distal anterior corner with two apically bifurcate macrochaetae, most of ventral face and anterior margin covered with lanceolate scales with setae restricted to the proximal posterior quarter. Tibia with a very strong carrot-shaped macrochaeta distally as well as a few smaller strong setae along the ventral margin, dorsal or outer margin with one or two macrochaetae about midway along the margin and another usually about ¾ the distance along the margin; apical spur large and distinctly hooked and bearing a few small setae; ventral face of tibia mostly covered with lanceolate scales. Tarsi of four articles, the basal tarsal article of PI about equal in length to the remaining articles together, bearing some stronger setae below; second and third articles short and subequal, suture between third and fourth articles weak. Pretarsus with two long curved lateral claws and a much shorter straight medial claw. PII ( Fig. 24 ) and PIII ( Fig. 25 ) similar to PI except lacking comb on the precoxa. The relative length of the basal tarsal article is progressively only a little longer, being about 56% of the total length on PIII.

Abdomen: Urotergite I ( Fig. 26 ) with 2+2 small combs, each lateral comb of two macrochaetae associated with a cilium, two small marginal setae and a setula, each sublateral comb of a single macrochaeta associated with a cilium and a small but stout marginal seta; urotergites II–VII with 3+3 combs ( Figs 27–30 ) as shown in table 3, each lateral comb associated with 2–3 cilia, 1–2 marginal setae and 0–3 setulae, each submedial comb associated with 1–3 cilia, 1–2 marginal setae and 0–2 setulae, each submedial comb of a single macrochaetae associated with two cilia and 0–1 setulae; urotergite VIII with 2+2 combs similar to those on the preceding segments, lacking the sublateral comb; urotergite IX ( Figs 31, 32 ) without combs but with 1–2 marginal setae, a cilium and 0–2 setulae in each infralateral corner. Urotergite X ( Fig. 33 ) straight and glabrous across the posterior margin, L/ W 0.38 –0.48, with1+1 stronger macrochaetae in each posterolateral corner and several strong macrochaetae some cilia and setulae along most of each lateral margin.

Urosternite I glabrous, urosternites II–VIII with 1+1 lateral combs each of a single macrochaeta each associated with a cilium laterad and posterior to the macrochaeta and usually with a setula closer to the margin ( Figs 34–36 ). Slender styli present on VIII and IX in male and VII to IX in female; each stylus with several robust macrochaetae apically. Styli IX ( Fig. 37 ) (excluding the apical macrochaetae) a little more than two times the length of the internal process.

Coxite IX of male IX ( Fig. 37 ) similar to female, inner process 3.1–3.4 times longer than outer process (2.5–2.8 times on K. 261294 from Norfolk Island), and 1.4 times longer than wide at its base (1.1–1.2 times on K. 261294 from Norfolk Island), bearing short parameres which have several short thin setae distributed over their surface ( Fig. 38 ). Penis typical ( Fig. 37 ) with numerous glandular setae apically, each set on a protuberance.

Coxite IX of ♀ ( Fig. 40 ), the internal process acute apically, about four times longer than the external process (range 3.8–4.3) and 1.7 times (range 1.7–1.8) longer than wide at its base, external and internal margins of internal process and external margin of outer process round with a few moderately strong insertions. — Ovipositor long about twice HW (range 1.7–2.3) surpassing the end of the inner process of coxite IX by about three times the length of the inner process, composed of about 40 divisions (range 34–42) and surpassing the apices of styli IX by about the length of the stylus on the specimen from Norfolk Island (K. 261292). Distal divisions of gonapophyses ( Fig. 41 ) with only short fine setae and setulae.

Cerci ( Figs 39 ) with four basal divisions shorter than wide then progressively longer with a single rosette of setae, macrochaetae and trichobothria becoming increasingly stronger and longer distally, fifth and sixth divisions with two rosettes, the more proximal with short trichobothria, smaller seta and what appear to be lanceolate scales, macrochaetae restricted to the most distal rosette; seventh division with three rosettes, the probable lanceolate scales restricted to the two basal rosettes; eighth division with four rosettes, the apparent lanceolate scales restricted to the first and third rosettes; eleventh division with eight rosettes, apparent lanceolate scales possibly restricted to the most basal rosette. — Median dorsal appendage ( Fig. 39 ) as illustrated.

Habitat. The type series was collected under bark of “Kilinogue” trees. Other LHI specimens were collected from a rotting log and the Norfolk Island specimen was collected by beating a dead branch. Presumably this species lives under bark or within other cavities on trees .

Remarks

Contrary to earlier opinion (e.g., Smith, 2014), H. howense is not a close relative of H. sclerophyllum regardless of its similar arrangement of styli, a character which should no longer be considered as a strong indicator of relationship. A specimen from Lord Howe Island mentioned by Smith, 2014 (K. 261088 K. 261089) has now been shown to belong to H. milledgei sp. nov. described below.

Heterolepisma howense appears to be closer to H. cooloola from the southern Queensland coastal forests, with which it shares the glabrous anterior margin to the frons, lanceolate scales on the femora and tibia and the arrangement of styli. Unpublished molecular data indicate there are several, as yet undescribed, species in the cooloola group along the eastern seaboard of Queensland suggesting north-eastern Australia may have been the origin of the colonising ancestor.

In addition to the characters given in the diagnosis to distinguish this species from H. cooloola , morphometric analysis also identified several measurements as potentially useful to separate the species, i.e. very little or no overlap in the range of measurements. These data need to be expanded to include more specimens from a wider geographical spread.

No consistent morphological difference could be found between the specimens collected on Norfolk Island and Lord Howe Island. It is also possible that the presence of this species on both islands (almost 900 km apart) is due to the activities of man. Ships regularly sailed between these islands in the 1800s (e.g., Nicholls, 2006) and possibly even earlier ( Anderson and White, 2001). If they were carrying wood collected on one or other island (e.g., as firewood) then silverfish may have been transported along with it. Heterolepisma howense may have been a Norfolk Island endemic or vice versa.

Figures

Figures 4–14. Heterolepisma howense Womersley specimen K.541011 K.541012 ♂ unless otherwise indicated by specimen number (4) dorsal scale; (5) lanceolate scale from femur; (6) head of paratype K.261040; (7) antenna, pedicel and basal intervals of flagellum; (8) idem, proximal four annuli of most distal surviving interval showing location of basiconic sensillum type B (bsB); (9) mandible; (10) idem, incisor and molar regions; (11) maxilla, only more prominent setae of palp illustrated; (12) idem, lacinia; (13) idem, apex of ultimate article of palp with its branched papillae (bp); (14) labium. Scale bars = 0.1 mm.

Figures 15–25. Heterolepisma howense Womersley specimen K.541011 ♂ unless otherwise indicated by specimen number (15) pronotum, anterior and left margins; (16) idem, right anterior trichobothrial area; (17) idem, right posterior trichobothrial area; (18) idem, right posterior comb; (19) mesonotum, left side; (20) idem, trichobothrial areas, left side; (21) metanotum, right side; (22) idem, trichobothrial areas, right side; (23) presternum, prothoracic sternum and PI; (24) mesothoracic sternum and PII; (25) metathoracic sternum and PIII. Scale bars = 0.1 mm.

Figures 26–38. Heterolepisma howense Womersley specimen K.541012 ♂ (26) urotergite I; (27) urotergite IV; (28) idem, right lateral comb; (29) idem, right sublateral lateral comb; (30) idem, right submedial comb; (31) urotergite IX, left infralateral comb; (32) urotergite IX, right infralateral comb; (33) urotergite X; (34) urosternite IV; (35) idem, right comb; (36) urosternite VIII, left stylus insertion; (37) urosternite IX, stylus and penis; (38) left paramere. Scale bars = 0.1 mm.

Figures 39–41. Heterolepisma howense Womersley paratype ♀ K.261041 unless otherwise indicated byspecimen number (39) base of cerci and medial dorsal appendage ♂ K.541012; (40) coxites VIII and IX and ovipositor; (41) apex of ovipositor valves. Scale bars = 0.1 mm.