Acrotelsella parlevar, 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 : 66-72

Acrotelsella parlevar n.sp.

Figs 122–163

Type material. Holotype ♀ ( HW 1.55 ) (K261103 K261104 on two 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. Both antennae of the holotype broken off above scape but there were four loose antennae in the original tube which also contained a specimen of another species (described below). There is little doubt that the correct antennae have been paired with the correct specimens due to the absence of poculiform sensillae in Acrotelsella species and their obvious presence in the other species and its nearest relative from Barrow Island. Similarly all styli of this species were lost but at least one stylus loose in tube is believed to be stylus IX of this species as it is much longer than the remaining stylus on the second species.

Diagnosis. This species can easily be distinguished from other described Acrotelsella by the presence of only three papillae on the last article of the labial palp, the shape of the thoracic sterna and the arrangement of the sternal combs in over-lapping subparallel rows.

Description. Appearance. Medium to large silverfish, with narrow body, thorax not much wider than the abdomen which only tapers slightly posteriorly ( Fig. 122 ). Scale pattern when live unknown, in alcohol mottled brown. Head covered with light brown scales; eyes dark chestnut, thorax and abdomen dorsally fairly evenly covered in brown scales.

Body length. H+B 10.7 mm (♀), HW 1.55 mm; thorax: length 3.5 mm or one third H+B; width 2.15 mm with the pronotum being slightly narrower than the meso- and metanota, mesonotum slightly longer than pronotum and shorter than metanotum; antennae incomplete, maximum preserved length 7 mm or>0.66 H+B; terminal filaments all broken, maximum length of cercus 1.8 mm or>0.17 H+B; median dorsal appendage maximum length 3.75 mm (>0.3 H+B).

Pigmentation. Antennae pigmented brown along entire length. Frons with reddish brown pigment on sides and extending somewhat in front of the isolated sublateral groups of macrochaetae, and a little around the eyes, scape with reddish brown pigment distally and along mediad face, mandibles, maxillae and labium without pigment, maxillary palp with pigment on articles two, three and four becoming increasingly darker, ultimate article not as dark, especially at both ends; labial palp with very little pigment, just a small amount apically on the margin of the penultimate article and faintly on the distal article, prothorax with pigmentation on anterior corners but not along the notal collar, thoracic sternites without pigment, legs with brown pigment on shoulder of coxae, posterior margin of trochanter, over face of femur and noticeably stronger on the margins especially distally, the tibia and basal article of tarsi with even, somewhat orange pigment, pinkish pigment on inner process of coxites IX, ovipositor without pigment, cerci and median filament evenly light.

Macrochaetae. Variable, pectinate or smooth ( Figs 123–125 ), hyaline to light brown.

Scales. With numerous sub-parallel ribs that do not surpass the margin of the scale ( Fig. 126 ), those dorsal brown, those ventral hyaline. Scales found on top of head, on scape, on second article of maxillary palp, all nota, all thoracic sterna, legs (except for trochanter and distal three articles of tarsi), all urotergites and urosternites, styli IX, medial filament and possibly also the cerci.

Head. ( Fig. 127 ) wider than long, with 1+1 not very dense bushes of macrochaetae aligned in subparallel rows on the anterolateral corners. There is a small gap in the row of macrochaetae along the margin above the antennal bases after which there is another bush of weakly pectinate to smooth macrochaetae, three or four macrochaetae wide extending along the sides and above the eye; the normally isolated group behind the antennae is almost connected with the lateral bushes. Clypeus with 1+1 very dense bushes of strongly pectinate macrochaetae as well as a few curved setae laterally. Labrum also with 1+1 dense bushes of pectinate macrochaetae as well as many simple setae and three longer thin setae. Eyes dark chestnut brown. —Antennae fairly long, scape ( Fig. 128 ) quite long with scales over surface and a preapical rosette of numerous setae; pedicel with preapical rosette of simple setae and cilia with two close rows of setae in places as well as setae scattered over face; first annulus/interval of flagellum with a subapical rosette of simple setae and probably two trichobothria; next annulus with two rosettes of simple setae each probably with two trichobothria; subsequent intervals with single rosette of setae and cilia across the middle of the annulus and two short trichobothria per annulus. Intervals of flagellum subdivided from the seventh interval. Distally the intervals are subdivided into six annuli ( Fig. 129 ) with the most distal annulus bearing a proximal rosette of setae and a subapical rosette of cilia, a trichobothrium and probably some rod-like basiconic sensillae. —Mandibles ( Figs 130, 131 ) typical for Acrotelsella with well-developed molar and incisor areas; a group of about fifteen strong apically bifurcated but simple setae distally adjacent to the pectinate molar area and a bush of about 120 macrochaetae externally as well as scattered simple setae and pectinate macrochaetae. —Maxilla ( Fig. 132 ) with some thick minutely apically bifurcated 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 eight lamellate processes and a row of eleven thin simple setae, those nearest the lamellate processes shorter and conical in shape, galea slightly longer than lacinia with about five strong, smooth, simple or apically bifurcate setae externally in its basal half and several cilia distally ( Fig. 133 ); maxillary palp very long and thin, apical article ( Fig. 134 ) five to six times longer than wide and 0.9 times as long as the penultimate article which is 0.87 times as long as the third and longest article, the ultimate article with a thick sausage-shaped sensilla subapically (thinwalled basiconic sensillae of Adel 1984), last three articles of palp with fine setae only, basal article with oblique rosette of thicker setae, second article also with subapical rosette of slightly thicker setae. —Labium ( Fig. 135 ) short and broad, postmentum with transverse row of apically bifurcate setae, prementum with transverse and oblique rows of short strong apically bifurcated setae, apically with long curved setulae; labial palp short, apical article expanded medially ( Fig. 136 ), a little shorter than long (0.80–1.00) with row of only three papillae of compact type arranged in a single row near the outer margin, with at least one thin-walled basiconic sensillae and some rod-like basiconic sensilla on the outer margin, covered with numerous fine setae as well as longer fine setae.

Thorax. Pronotum ( Fig. 137 ) with dense setal collar about three to four macrochaetae wide, with very slight gap medially, all macrochaetae lost except a few at the lateral ends which are short and slightly pectinate; lateral margins with a few setae along the margin (all macrochaetae lost except one which is short and slightly pectinate), these marginal setae almost absent from the anterior part of the margin, becoming more frequent posteriorly, with eight combs of two to three macrochaetae along each margin (all lost except one from the most anterior comb of the metanotum which is strongly pectinate). Two open trichobothrial areas; the posterior trichobothrial area is located about ¾ of the distance along the margin and is associated with the last comb (=N using terminology of Molero-Baltanás et al, 2010), this comb composed of three macrochaetae with the short trichobothrium at the mediad end and a cilium at the laterad end, the anterior trichobothrial area is slightly forward of the midpoint 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 at the mediad side of the macrochaeta; all combs associated with a few setulae. Posterior margin with 1+1 combs of eight macrochaetae associated with several setulae between the comb and the margin and a cilium at the mediad end. —Mesonotum ( Fig. 138 ) with lateral chaetotaxy similar to pronotum with ten combs of two to four macrochaetae, the anterior trichobothrial area ( Fig. 139 ) located a little more than half way along the lateral margin associated with comb N-2 composed of two macrochaetae with the trichobothrium located between the macrochaeta and the margin, with one to three setulae posterior to the comb and a cilium between the trichobothrium and the margin. Posterior trichobothrial area ( Fig. 140 ) slightly more posterior than that on the pronotum, the trichobothrium located mediad to the comb of two macrochaetae and with one to three setulae posterior to the comb. Posterior margin with quite laterad 1+1 combs ( Fig. 141 ) of nine to ten macrochaetae with cilia at each end and several setulae between the comb and the margin. —Metanotum ( Fig. 142 ) similar to mesonotum with nine or ten combs of two to four macrochaetae, the anterior trichobothrial area associated with comb N-1 of two macrochaetae about two thirds the distance along the margin, the posterior trichobothrial area associated with the most posterior comb and the posterior 1+1 combs each of nine macrochaetae with a cilium at each end and several setulae between the comb and the margin.

Presternum narrow, with transverse row of setae ( Fig. 143 ). —Prothoracic sternum ( Fig. 143 ) large, almost as long as the coxa, 1.1 times as long as wide at its base, parabolic, rounded apically, anterolateral corners with fields of about 40 simple small setae, those on the margins finer than those submarginal, posterior three quarters of lateral margins with fringe of setae and some cilia as well as seven to eight short combs each composed of four to twelve setae mostly arranged in two to three overlapping rows ( Fig. 144 ). — Mesosternum ( Figs 145, 146 ) a little larger than prosternum (1.1 times as long) and slightly less acute apically, a little longer than wide at its base, with a few fine setae in the anterolateral corners and long, thin simple marginal setae along the posterior quarter of the margin and 2+2 combs distally, the more anterior composed of 13–16 pectinate macrochaetae in two rows, the more posterior composed of seven to eleven pectinate macrochaetae also in two rows. — Metasternum ( Figs 147, 148 ) of similar size to mesosternum except wider, apically rounded, the margins slightly concave adjacent to the posterior combs, about 1.2 times wider than long wide with marginal setae and cilia along distal sixth of lateral margins and 1+1 groups of 18–19 pectinate macrochaetae arranged in three or four overlapping rows plus 1+1 single submarginal macrochaetae more distally.

Legs quite long and slender, tibia L/W ratio of legs PI 3.1, PII 3.1, PIII 4.4; tarsi L/W ratio PI 7.0, PII 6.8, PIII 11.7. PI ( Fig. 149 ) with a row of setae laterally on the distal margin of the precoxa. Coxa with scales and a group of about fifteen macrochaetae on the anterolateral corners followed by a field of strong pectinate macrochaetae along the external margin; inner margin with a four lightly pectinate macrochaetae and numerous smooth and pectinate setae of varying thickness distally over the articulation. Trochanter with a few setae. Femur posteriorly with nine (?) strong, thick slightly pectinate carrot-shaped macrochaetae, in addition to simple setae along the margin and just a few on the dorsal surface towards the distal end. Tibia of PI with about six stout, carrot-shaped, slightly pectinate macrochaetae along the posterior margin as well as several longer, thinner, pectinate or smooth setae and a row of shorter setae near the distal margin; anterior margin with two pectinate macrochaetae as well as about two subdistal macrochaetae over the articulation, dorsal surface with a subdistal row of setae; apex of tibia with the usual apical spur which is covered in numerous 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 particularly oblique, the surface of all tarsal articles with numerous simple setae, the second article on both PI legs appearing to have a raised oval area basally (perhaps an artefact or a sensilla). Pretarsus with two long curved lateral claws and a shorter curved medial claw. PII and PIII ( Fig. 150 ) similar to PI except the anterolateral groups of macrochaetae on the coxa reduced to about seven setae in two rows; legs progressively longer from PI to PIII and the relative length of the basal tarsal article is progressively longer, being about two thirds of the total length on PIII.

Abdomen. Urotergite I with 1+1 lateral combs of eight to nine macrochaetae each associated with a cilium at either end and several setulae between the comb and the margin, urotergites II–VII with 3+3 combs of macrochaetae as in Table 2 ( Figs 151–154 ), urotergite VIII with 2+2 combs (lacking the sublateral), urotergite IX glabrous; all combs with a cilium at either end and a similar number of setulae as macrochaetae between the comb and the margin. Urotergite X ( Fig. 155 ) acutely triangular, slightly wider at base than long (L/W 0.80) with many setae along entire margin both above (all lost) and below (small, simple), and 5+4(5) combs of one to six macrochaetae per comb (all lost) as well as several setulae posterior to each comb, and most combs with a cilium at the mediad end.

Urosternite I and II glabrous, urosternites III–VII with 1+1 lateral combs of 16–21 pectinate macrochaetae ( Figs 156, 157 ) each with 11–19 setulae between the comb and the margin as well as a cilium at each end of every comb. The distance between the lateral combs 2.7–4.6 times the average width of these combs, the ratio being largest on urosternite III and decreasing posteriorly.

Genital region of ♀ as in Fig. 158 . Two pairs of styli, those on IX long and slender with robust setae apically and along the length of the stylus ( Fig. 159 ), styli of VIII lost. Coxites VIII with long combs of 18 macrochaetae and a similar number of setulae between the comb and the margin, the coxites with rounded inner corners. Coxites IX with long rounded internal process, about 3.7 times longer than wide at its base and almost eight times longer than the short pointed external process, the inner processes not quite reaching the apex of the ovipositor; outer process with setulae along the inner margin and several setae externally, inner process with several long smooth setae along the outer margins as well as finer setae or setulae and many scales, inner margin of process with setae insertions (all setae lost) and many small setae or setulae. —Ovipositor ( Figs 158, 160 ) not very long (up to 1.9 HW), only just surpassing the apex of the long internal processes of coxites IX, both pairs of gonapophyses consisting of longer basal divisions becoming progressively shorter distally, about twenty divisions in total; of primary type with rows of fine setae on each article ( Fig.160 ) .

Cerci ( Figs 161, 162 ) first division glabrous, following five basal divisions shorter than wide then progressively longer with increasing numbers of rosettes of setae, macrochaetae and many trichobothria; most distal surviving division (twelfth) with four annuli each with a strong rosette; scales not observed on cerci but most setae and macrochaetae have been lost so scales may also have been lost. —Median dorsal appendage ( Figs 161, 163 ), first division glabrous, following divisions with rosettes of setae and trichobothria, formed into four annuli by thirteenth until at least the last surviving division (17th), scales present on some basal divisions (e.g., 7th, 8th, 9th).

Male. Unknown.

Habitat. Both this specimen and that of the following species were collected in a single pitfall trap in an area described as dry sclerophyll forest dominated by Eucalyptus viminalis , and E. amygdalina and Exocarpos cupressiformis with a grassy understorey ( Poa and Themeda ). The soil was very rocky.

Etymology. The species is named parlevar , one English language spelling of the name (treated as noun) of the indigenous occupants of Tasmania at the time Europeans first arrived.

Remarks. With seven described and numerous undescribed species, the genus Acrotelsella is well represented in Australia, especially in the warmer regions. The genus is also known from south-eastAsia, India and China, the Seychelles, Kenya, Madagascar, Somalia, Saudi Arabia, Hawaii, French Polynesia, Central and northern South America ( Colombia, Venezuela, Ecuador and Panama) and the Caribbean. This record is by far the most southerly for the genus. The mean annual rainfall is 703 mm, the monthly summer maximum temperature (for Launceston) is about 25 ° C and the mean winter minimum is 2.3 ° C.

The systematics of the genus is poorly understood and it will be necessary to describe many more species before a coherent phylogeny emerges. John Irish (pers. comm.), examined a range of specimens borrowed from various Australian museums and noted a group of species with only three papillae on the last article of the labial palp. Acrotelsella parlevar has this feature as do several other species collected by the current author and they may prove to be a distinct group within Acrotelsella .

Figures

Figures 122–131. Acrotelsella parlevar n.sp. holotype ♀ (122) habitus with separated antennae drawn as if attached; (123) long pectinate macrochaeta of clypeus; (124) finely pectinate macrochaeta of side of head; (125) carrot-shaped finely pectinate macrochaeta of tibia of PIII; (126) darker dorsal scale; (127) head (cross-hatched area obscured by eye pigment); (128) antenna, scape, pedicel and basal intervals of flagellum (graphically reconstructed joining loose antennae to scape); (129) idem, most distal surviving complete interval; (130) mandible; (131) idem, molar and incisor region. Scale bars = 0.1 mm unless otherwise indicated.

Figures 132–142. Acrotelsella parlevar n.sp. holotype ♀ (132) maxilla; (133) idem, lacinia and galea; (134) idem, apex of ultimate article of palp; (135) labium; (136) idem, ultimate article of palp showing location of thin-walled sensilla (tws); (137) pronotum; (138) mesonotum; (139) idem, anterior trichobothrial area; (140) idem, posterior trichobothrial area with fine line delineating extent of scale coverage; (141) idem, left posterior comb; (142) metanotum. Scale bars = 0.1 mm.

Figures 143–154. Acrotelsella parlevar n.sp. holotype ♀ (143) presternum, prothoracic sternum; (144) combs of prosternum; (145) mesothoracic sternum; (146) combs of metasternum; (147) metathoracic sternum; (148) combs of metasternum; (149) PI; (150) PIII; (151) urotergite VII; (152) idem, right lateral comb; (153) idem, right sublateral comb; (154) idem, right submedial comb. Scale bars = 0.1 mm.

Figures 155–163. Acrotelsella parlevar n.sp. holotype ♀ (155) urotergite X; (156) urosternite VI; (157) idem, right lateral comb; (158) coxites VIII and IX with ovipositor; (159) stylus IX; (160) apex of gonapophyses; (161) base of cerci and medial filament; (162) cercus, most distal surviving division; (163) medial filament, most distal surviving division. Scale bars = 0.1 mm.