Hemitelsella clarksonorum, Smith, 2016

Smith, Graeme B., 2016, On some Silverfish Taxa from Tasmania (Zygentoma: Lepismatidae and Nicoletiidae), Records of the Australian Museum 68 (2), pp. 45-80 : 73-79

Hemitelsella clarksonorum n.sp.

Figs 164–204

Type material. Holotype ♂ ( HW 1.18 ) (K261105 K261106 K261107 on three slides) TAS: Travellers Rest, near Launceston, 41.49103°S 147.07778°E, 17–23 April 2015, W. and L. Clarkson, pitfall trap, dry sclerophyll forest. Note that the antennae, excluding the scape, of both this specimen and that of the previous species were loose in the same tube. Given the colouring and the presence of large poculiform sensillae on the antennae (as in the closely related Hemitelsella transpectinata ) there is little doubt that the antennae have been matched with the correct species. This may not be the case for a leg and the styli mounted on the same slide.

Diagnosis. This species can easily be distinguished from Hemitelsella transpectinata (Smith) by the elongate shape of the ultimate article of the labial palp, the arrangements of combs on the thoracic sternites and the scale pattern of the head (lacking hyaline scales around the margin).

Description. Appearance. Medium sized silverfish, with narrow body, thorax not much wider than abdomen which only tapers slightly posteriorly from about the fifth abdominal segment; appearance when live unknown, in alcohol reddish brown. Head uniformly covered with brown scales, without wide areas of hyaline scales along the sides and front of the head; thorax also fairly evenly covered in brown scales although those along the posterior margin are larger and darker, abdomen with two longitudinal darker stripes formed by dark chestnut to black scales, along the first five segments with lighter coloured scales between and outside the lines, with a distinct patch of white scales in the posterior lateral corner of all segments, but larger and more conspicuous on segments II–VI, the lines merge together by the sixth segment to give an almost overall darker covering with the exception of the posterolateral white patches ( Fig. 164 ); eyes dark chestnut brown.

Body length. H+B 7.15 mm; HW 1.18 mm; thorax: length 2.35 mm or 0.33 H+B; width up to 1.48 mm with no great difference between the pro, meso- and metanota although the metanotum is the widest and the pronotum the narrowest, pronotum slightly shorter than meso- or mesonota; antenna almost complete, 6.0 mm or 0.85 H+B; terminal filaments all incomplete, maximum length of cercus remaining 5 mm or 0.7 H+B; maximum length of median dorsal appendage remaining 3.0 mm or 0.42 H+B.

Pigmentation. Body overall with a reddish brown appearance due to a reddish granular layer beneath the cuticle which easily peels away from it during dissection. Top of head evenly brown, scape brown, body of mandibles, maxillae and labium evenly pigmented, maxillary palp with pigment on all articles, somewhat less in distal articles, labial palp with very little pigment, just a bit more noticeable laterally on the distal article, legs with brown/orange pigment stronger towards outer margins and on distal end of all articles including tarsomeres; prothorax with more pigmentation along notal collar, all nota, urotergites and sternites appear to be evenly pigmented due to underlying reddish granular layer, penis with pigment around base and sides, pigment much less on inner process of coxites IX, styli without pigment, cerci and median filament evenly brown, the cerci darker than the median filament.

Macrochaetae. Pectinate and of variable form ( Figs 165–167 ), mostly hyaline but some on the tibia, as well as the rounded tip macrochaetae of the tarsi are more strongly sclerotized and darker, straw coloured or slightly brown.

Scales. With numerous subparallel ribs that do not surpass the margin of the scale but which can be quite different in their spacing ( Figs 168–170 ); hyaline scales with rays a little further apart than those of darker scales; shape of scales generally round, although the posterior margin can be quite straight for those scales overhanging the posterior margins of the tergites and others are shaped to fit around setae or combs. Scales found on top of head, base of mandibles, on scape, all nota, all thoracic sterna, legs but appear to be absent from trochanter and tarsi (except possibly the basal article of the tarsus of PIII), present on all urotergites and urosternites, styli and on parts of the terminal filaments. Scales of the terminal filaments very diverse in shape including some very broad as well as lanceolate scales.

Head. Wider than long ( Fig. 171 ), with 1+1 weak bushes of pectinate macrochaetae on the anterolateral corners, not very dense and not aligned in distinct rows. The gap along the margin above the antennae is very indistinct after which the marginal row continues about two to three macrochaetae wide to the level of the eyes and then running above the eyes with a small group of three or four macrochaetae above and behind the eyes. The small isolated 1+1 groups of macrochaetae posterior and mediad to the antennal base consist of only three to six macrochaetae without any associated cilia or long thin setae; 1+1 isolated single cilia are found anterior to and mediad to these groups. Clypeus with 1+1 bushes of about 20–25 macrochaetae as well as 1+1 setae between the groups. Labrum also with 1+1 bushes of pectinate macrochaetae as well as many simple setae and four thin setae anteriorly. —Scape of antenna ( Fig. 172 ) quite long with scales over surface and short robust simple anteapical setae, pedicel with two rosettes of setae, first annulus/interval of flagellum with two rosettes of setae (perhaps partially subdivided interval), most distal rosette also with two trichobothria, basal rosette with one trichobothrium, next two intervals with single rosette of setae transversely across the middle of the annulus and two short trichobothria per interval, the following interval with two rosettes, the basal with trichobothria, the following intervals beginning to form into annuli and the joints between the annuli are often indistinct incorrectly appearing almost as if there are very long intervals with several rosettes of setae, trichobothria and cilia ( Fig. 172 ). Subsequent intervals with increasing numbers of annuli with three or four rosettes of setae, the most distal with three trichobothria. Intervals with poculiform sensillae from about one quarter the length of the flagellum, initially smaller but becoming larger and apparently more numerous distally. Most distal intervals ( Fig. 173 ) divided into repeated patterns of eight annuli, the most proximal three annuli of each with two poculiform sensillae, the next with none (or perhaps one small), then two then none then two then none; all apparently without rod-like basiconic sensillae. —Mandibles ( Figs 174, 175 ) typical for Ctenolepismatinae with well-developed molar and incisor areas; a group of about fifteen strong and short or thin and longer, apically bifurcated setae distally adjacent to the pectinate molar area and a bush of about 20 macrochaetae externally. —Maxilla ( Fig. 176 ) with some thick apically bifurcate but otherwise smooth macrochaetae externally proximal to the palp, the lacinia with three strong teeth, one set further back than the other two, followed by about five lamellate processes and a row of eight thin simple setae, galea with several strong, smooth, pointed setae externally in its basal half and a few cilia distally; apical article of maxillary palp ( Fig. 177 ) 3.7 times longer than wide and only slightly longer than the penultimate article, the ultimate article with a rod-like basiconic sensilla and possibly a small poculiform sensillae near it, last three articles of palp with fine setae only, two basal articles with subapical rosettes of slightly thicker setae. —Labium ( Fig. 178 ) wider than long, postmentum with transverse row of smooth apically bifurcate setae, prementum with lateral and oblique groups of strong apically bifurcated setae and with short curved setulae distally; labial palp with subrectangular apical article, not greatly widened medially ( Fig. 179 ), 1.3 times longer than wide with row of eight or nine papillae arranged in a single curved row, possibly with one or two poculiform sensillae as indicated in Fig. 179 , one on the outer and one on the inner margin, covered with numerous fine short setae as well as longer fine setae on along the distal end; penultimate article almost as long as the ultimate article.

Thorax. Pronotum ( Fig. 180 ) with narrow setal collar about two macrochaetae wide and some small cilia; lateral margins with many setae (only insertions remain) as well as some submarginal setulae, posterior trichobothrium ( Fig. 181 ) at the mediad end of a submarginal comb of three macrochaetae located about ¾ of the distance along the margin of the pronotum (= N), comb N-1 is composed of one or two macrochaetae, comb N-2 (about half way along the margin) is composed of one macrochaeta with the anterior trichobothrium ( Fig. 182 ) located between it and a macrochaeta on the margin. There are three or four more submarginal combs of two to three macrochaetae anterior to the anterior trichobothrial area. Posterior margin with 1+1 single macrochaetae each associated with a marginal seta and a cilium ( Fig. 183 ), the posterior combs being positioned quite laterally and almost contiguous with the chaetotaxy of the lateral margin; the posterior macrochaeta and its insertion not present on right side of holotype. —Mesonotum ( Fig. 184 ) with lateral chaetotaxy similar to pronotum with eight combs of one to three pectinate macrochaetae, the anterior trichobothrial area ( Fig. 185 ) located about two thirds the way along the lateral margin, associated with comb N-2 of just one macrochaeta with the trichobothrium located between the macrochaeta and the margin and with a cilium between the trichobothrium and the seta on the margin. Posterior trichobothrial area ( Fig. 186 ) slightly more posterior than that on the pronotum, the trichobothrium located mediad to a group of three macrochaetae (= N) arranged in a triangle not in a line, (this unusual arrangement occurs on both sides of the mesonotum only; without more specimens it is not possible to say whether this is a characteristic of the species or just an aberrant individual). Posterior margin with quite laterad 1+1 combs each of a single macrochaeta with a cilium at the outer end and a marginal seta. —Metanotum ( Fig. 187 ) similar to mesonotum but with only seven combs of one or two macrochaetae, the anterior trichobothrial area associated with the comb (N-1) of just one macrochaeta about two thirds the distance along the margin, the posterior trichobothrial area associated with the most posterior comb (N) of two macrochaetae and the posterior 1+1 combs again quite laterad with one or two macrochaetae, a laterad cilium and a marginal seta.

Presternum narrow, with transverse row of strong pectinate macrochaetae ( Fig. 188 ). All thoracic sterna with hyaline scales. —Prothoracic sternum ( Figs 188 , 189 ) wider at base than long, subtriangular, rounded posteriorly, anterolateral corners with fringe of fine simple setae, posterior three quarters of lateral margins with long fine simple setae as well as 3+3 combs of five to seven pectinate macrochaetae. —Mesosternum ( Figs 190, 191 ) slightly wider than and about one and a half times longer than the prosternum, about as long as wide at its base, with long, thin simple marginal setae and 2+3 combs in its distal third, composed of three to eight shorter and longer pectinate macrochaetae. —Metasternum ( Fig. 192, 193 ) apically rounded, about 1.2 times wider than long with long marginal setae and cilia along distal ¼ of lateral margins and 2+2 combs of longer and shorter pectinate macrochaetae.

Legs ( Figs 188 , 190, 192 ) becoming progressively longer and more slender, tibia L/W ratio of legs PI 2.65, PII 3.3, PIII 4.2; tarsi L/W ratio PI 4.9, PII 7.4, PIII 10.7. PI ( Fig. 188 ) with comb of five macrochaetae laterally on precoxa. Coxa with scales and a comb of about six macrochaetae on the anterolateral corners followed by many strong pectinate macrochaetae along the external margin, sometimes grouped into combs of two macrochaetae, the more marginal macrochaetae being much less pectinate, curved carrotshaped; inner margin with two setae and a long thin seta on the dorsal face and about five setae of varying thickness distally over the articulation. Femur ventrally with several strong, thick pectinate macrochaetae and dorsally with three pectinate macrochaetae over the articulation in addition to fine setae scattered over the mediad half of the dorsal surface. Tibia of PI with numerous long carrot-shaped, slightly pectinate macrochaetae along most of the ventral margin and several shorter stout, apically round setae in the distal half, not forming a row parallel to the margin; external margin with group of stout setae about half the distance along the margin; apex of tibia with two stout pectinate macrochaetae and the usual apical spur which has one stout, round-tipped seta as well as a few small denticulations on the posterior margin. Tarsi of four articles, the basal tarsal article of PI about 40% of the total length of the tarsus, its join with the next article not particularly oblique, the ventral face of all tarsal articles with apically rounded, stout setae which are longer near the apex of each article, dorsally with some simple setae. Pretarsus with two long curved lateral claws and a much shorter curved medial claw. PII ( Fig. 190 ) and PIII ( Fig. 192 ) similar to PI except lacking the anterolateral comb on the coxae; legs progressively longer from anterior to posterior with the tibia of PII being 1.5 times longer than that of PI and the tibia of PIII being 2.15 times longer than that of PI, the relative length of the basal tarsal article is progressively longer, being about 60% of the total length on PIII.

Abdomen. Urotergite I with 1+1 lateral combs of three macrochaetae each comb associated with one or two marginal setae and a cilium at the laterad end of the comb, urotergites II–VII ( Figs 194–197 ) with 3+3 combs of macrochaetae as in Table 3, the lateral combs with pectinate macrochaetae (all lost in other combs) also associated with 2–3 marginal setae or setulae and one or two cilia, almost always at the laterad end of the comb but often at both ends, the sublateral combs usually associated with 0–2 marginal setae or setulae (all lost) and occasionally a cilium at the mediad end, the submedial combs associated with 0–1 marginal setae or setulae and with a cilium at the laterad end of the comb; urotergite VIII with 2+2 combs, lacking the sublateral comb; urotergite IX glabrous. Urotergite X ( Fig. 198 ) subtriangular with rounded apex, wider than long (L/W at base about 0.50) with many fine setae along entire margin as well as some stronger weakly pectinate setae close to the margins; with 3+3 combs of one or two macrochaetae per comb (all macrochaetae lost) with rare setulae posterior to the combs.

Urosternite I and II glabrous, urosternites III–VIII with 1+1 lateral combs of five to nine pectinate macrochaetae ( Figs 199, 200 ) each usually associated with one to five thin marginal setae or setulae and rarely a cilium at the laterad end of the comb (only segments VII and VIII). The distance between the lateral combs 4–11 times the average width of these combs, the ratio being largest on urosternite III and decreasing posteriorly.

Each coxite IX ( Fig. 201 ) with obvious transverse comb of sixteen macrochaetae across the inner process and four macrochaetae on the face posterior to the transverse comb; the internal process not acute nor elongated, about four times longer than the external process but only about two thirds as long as broad at its base; external and internal margins of internal process and external margin of outer process with many long, thin, often pectinate setae arising mostly from the dorsal face of the margin. Outer process small, acute triangular with a few setae along the outer margin. Only one pair of long slender styli ( Fig. 201 ) present ( IX); each stylus with about two short robust round-tipped macrochaetae apically. Styli IX in male holotype (excluding the apical macrochaetae) about three times the length of the internal process. Penis typical ( Fig. 201 ) with numerous glandular setae apically, each set on a protuberance; with small three- or four-armed papillae located on either side of opening. Parameres absent .

Cerci ( Figs 202, 203 ) with five basal divisions shorter than wide then progressively longer with setae, macrochaetae and trichobothria becoming increasingly stronger and longer distally until the eleventh when the long trichobothria are no longer visible and the remaining macrochaetae are shorter; most macrochaetae on the cerci are simple not pectinate except for one mediad and subapical on each division; divisions from about the seventh with two rosettes and three annuli; the number of these annuli increases progressively (seven in the tenth, eleven in the thirteenth and fifteen in the fifteenth) with setae and scales (both lanceolate and wider) at various locations as shown in Fig. 203 . —Median dorsal appendage ( Figs 202, 204 ) with long first division bearing 1+1 small setae and two further rosettes of small setae and trichobothria, the setae above simple while those below are very pectinate, following divisions also short with setae and trichobothria in increasing numbers, scales visible at sides on the surfaces proximad to each rosette from the fifth division becoming less numerous and conspicuous distally, divisions begin to form into annuli by about the sixth division, having about five annuli by the tenth and eleventh divisions (most distal surviving divisions) ( Fig. 204 ).

Female. Unknown.

Habitat. As for Acrotelsella parlevar with which it was collected in a single pitfall trap in an area described as dry sclerophyll forest dominated by Eucalyptus viminalis , E. amygdalina and Exocarpos cupressiformis with a grassy understorey ( Poa and Themeda ). The soil was very rocky. Ants of the genera Iridomyrmex and Melophorus were also found in the pitfall trap but no association is suspected.

Etymology. The species is named for the collectors of the species, Wade and Lisa Clarkson.

Remarks. The only other species yet described of this genus is Hemitelsella transpectinata (Smith) from Barrow Island. Superficially there seems to be very little in common regarding the habitat of these two species with Barrow Island being extremely hot and arid most of the time, while the Tasmanian site is cool and temperate. The single Tasmanian specimen and all 170 specimens from Barrow Island were collected in pitfall traps, suggesting the species is quite mobile living in leaf litter, under stones or cracks within the soil.

Figures

Figures 164–177. Hemitelsella clarksonorum n.sp. holotype ♂ (164) habitus, with loose antennae drawn as if attached; (165) smooth, apically bifurcate seta of prementum; (166) pectinate macrochaetae of coxa of PIII; (167) round-tipped macrochaeta from apex of tibia of PIII; (168) darker scale from face of pronotum; (169) darker scale from margin of pronotum; (170) hyaline scale from mesonotum; (171) head (cross-hatched area obscured by eye pigment; (172) antenna, scape, pedicel and basal intervals of flagellum (graphically reconstructed joining loose antennae to scape); (173) idem, most distal surviving interval showing poculiform sensillae (ps); (174) mandible; (175) idem, incisor and molar regions; (176) maxilla, smaller setae omitted; (177) idem, ultimate article of palp showing possible poculiform sensilla (ps?) and thin-walled sensilla (tws). Scale bars = 0.1 mm unless otherwise indicated.

Figures 178–188. Hemitelsella clarksonorum n.sp. holotype ♂ (178) labium, minor seta of palp omitted; (179) idem, ultimate article of palp showing location of possible poculiform sensillae (ps?); (180) pronotum; (181) idem, right posterior trichobothrial area; (182) idem, left anterior trichobothrial area; (183) idem, left posterior comb; (184) mesonotum; (185) idem, left anterior trichobothrial area; (186) idem, left posterior trichobothrial area; (187) metanotum; (188) presternum, prothoracic sternum and PI. Scale bars = 0.1 mm.

Figures 189–193. Hemitelsella clarksonorum n.sp. holotype ♂ (189) combs of prosternum; (190) mesothoracic sternum and PII; (191) combs of mesosternum; (192) metathoracic sternum and PIII; (193) combs of metasternum. Scale bars = 0.1 mm.

Figures 194–204. Hemitelsella clarksonorum n.sp. holotype ♂ (194) urotergite V; (195) idem, left lateral comb; (196) urotergite II, left sublateral comb; (197) idem, left submedial comb; (198) urotergite X; (199) urosternite III; (200) idem, left submedial comb; (201) coxite IX with stylus and penis showing location of papillae (p); (202) base of cerci and medial filament, showing scales (sc); (203) most distal surviving part of cercus showing round (rsc) and lanceolate (lsc) scales; (204) most distal surviving division of median filament (tenth division). Scale bars = 0.1 mm.