Heterolepisma pyramidum, Smith & Mitchell, 2019
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: 158-164
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Heterolepisma pyramidum sp. nov.
Holotype. ♀ ( HW 1.20) ( AM K.261254 K.261255 on two slides) LORD HOWE ISLAND: Balls Pyramid, rock platform at southern tip “Base Camp”, 31.7575°S 159.2550°E, 26.iii.2017, F. Koehler. GoogleMaps
Diagnosis. This species can be distinguished from many species of Heterolepisma by the absence of macrochaetae along the anterior margin of the frons, by the presence of lanceolate scales on the clypeus, femora, tibia and terminal filaments and the presence of a medial comb on urosternite I. Within the remaining group of several species that definitely have these characters ( H. bisetosum , H. parvum , H. heraldense sp. nov. and H. serranoi ) and others that probably have these characters ( H. exacta , H. japonicum , H. mossambicense , H. primafrum and H. rouxi ), H. pyramidum sp. nov. can be distinguished from all by a combination of the number of macrochaetae in the posterior combs of the nota (one rather than two), the absence of a macrochaeta associated with the anterior trichobothrial area of the pronotum, the composition of the urosternal combs being of greater than a single macrochaeta, the arrangement of styli (three pair in the ♀ and only two pair in the ♂) and the lesser number of combs on urotergite I (2+2 vs 3+3).
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 ( Fig. 86 View Figures 86–98 ).
Body length: H+B 8.9 mm; HW 1.20 mm; thorax: length 2.5 mm or 0.28 H+B; width up to 1.85 mm, widest at the mesonotum, pronotum and mesonotum slightly longer than the metanotum; antennae almost complete at 5.3 mm or 0.59 H+B; cerci and median dorsal appendage almost complete at 5.2 mm and 5.9 mm (0.58 and 0.67 H+B) respectively.
Pigmentation: Pigment brownish. Flagellum of antennae evenly light brown becoming slightly darker distally; pedicel
and H. milledgei sp. nov. Number of specimens within parentheses. without pigment, scape with small patch of pigment above as well as on its insertion pedestal. Terminal filaments annulated darker brown with only the portion of each major division distad of the rosette of larger macrochaetae unpigmented (e.g., the distal end of every eighth subdivision distally). Head with pigment around eyes and along lateral margins to the level of the perpendicular band of macrochaetae. Maxillary palp with light pigment on distal article, penultimate article and third article with even pigmentation, but much less on the second article. Ultimate article of labial palp with light pigment along lateral margins, penultimate article more pigmented, especially laterally and a small amount of pigment on external margin of second article. Precoxae with pigment and dark scales, coxae with light pigment only along lateral margins, trochanter without pigment, femur with small area of pigment distally on the leading edge as well as along the posterior margin, tibia with pigment over much of surface but darker on the dorsal margin, first tarsal article pigmented. Urotergite X and coxites IX pigmented. Styli IX with light pigment distributed evenly. Ovipositor white or perhaps slightly yellowish.
Macrochaetae: Smooth, hyaline to straw-coloured to moderate brown, apically bifurcate with truncated tips to each bifurcation ( Fig. 87 View Figures 86–98 ). Some macrochaetae on tibia, stout carrot-shaped ( Fig. 88 View Figures 86–98 ).
Scales: Quite broad, brown with numerous subparallel ribs that do not surpass the margin of the scale ( Fig. 89 View Figures 86–98 ). Scales found on top of head, some, either side of the tiny medial setae protruding well beyond the anterior margin; scales absent from clypeus and labrum as well as all cephalic appendages; dark scales present on all nota and abdominal tergites, clear scales on all thoracic and abdominal sterna, and coxae of legs, absent from styli. Lanceolate scales present on all femora and tibia; other leg articles without scales; lanceolate scales also present on basal third of the terminal filaments (except basal few divisions).
Head: Wider than long ( Fig. 90 View Figures 86–98 ), without distinct bushes. Anterior margin without macrochaetae except for four tiny setae in the middle; strong macrochaetae along lateral margins with peri-antennal groups of about seven macrochaetae which are contiguous laterally with the rows of macrochaetae along the margin, the marginal macrochaetae continue along the sides of the head behind the antennae with a line of four or five macrochaetae lying above the eyes. Clypeus with some longer macrochaetae and several setae extending across the face. Labrum with many setae across the proximal half and a line of six thinner setae anteriorly. — Scape quite short with a subdistal line of setae and smaller setae over the dorsal anterior face, pedicel ( Fig. 91 View Figures 86–98 ) short, also with a subapical rosette of small macrochaetae with setae scattered over the surface medially; first annulus of flagellum apparently glabrous, subsequent annuli with a rosette of small setae and some short trichobothria, the divisions between the annuli difficult to discern in the slide mounted material, the intervals split into two annuli by the 7th interval, into four by the 12th and into eight by the 17th. Most distal surviving intervals ( Fig. 92 View Figures 86–98 ) divided into repeated patterns of eight annuli, each with two rosettes of setae, those basally long tapering, those distally thinner and almost parallel-sided, the apical article of each interval has at least one trichobothrium, the second and fourth annuli bear at least one long, sausage-shaped basiconic sensillum (Type C of Adel, 1984). — Mandibles ( Figs 93, 94 View Figures 86–98 ) typical for Heterolepismatinae with well-developed molar and incisor regions; a group of about six strong and short plus five thinner, apically bifurcated setae distally adjacent to the molar region and a bush of about 40 macrochaetae externally. — Maxilla ( Fig. 95 View Figures 86–98 ) with three apically bifurcate macrochaetae externally proximal to the palp; lacinia short and wide, with three strong teeth, one set further back than the other two, followed by about seven lamellate processes and a row of seven setae, galea with only short fine setulae ( Fig. 96 View Figures 86–98 ); apical article of maxillary palp ( Fig. 97 View Figures 86–98 ) 4.6 times longer than wide and 1.2 times longer than the penultimate article, the ultimate article with three branched papillae, other specialised sensilla (e.g., basiconic sensilla) not seen, last three articles of palp with fine setae only, two basal articles with subapical rosettes of thicker setae. — Labium ( Fig. 98 View Figures 86–98 ) wider than long, postmentum with setae scattered in band across entire width including several small setae along and near the anterolateral margins, prementum with transverse and oblique groups of strong setae and with short setulae distally; apical article of labial palp ( Fig. 99 View Figures 99–108 ), about as wide as long (L/ W 0.95), with five papillae of the compact type arranged in a broad three plus two cluster arrangement, the distal three arranged in a curved line, a single basiconic sensillum (Type C) on the outer margin near the level of the papillae, covered with numerous fine short setae especially below; penultimate article with some stronger setae on the bulge medially; second article also with stronger setae along the inner margin and a subapical rosette; basal article with an apical line of stronger setae ventrally.
Thorax: Pronotum ( Fig. 100 View Figures 99–108 ) with complete setal collar of short macrochaetae and some cilia; setae of lateral margins lost, but consisting of some marginal setae as well as cilia and two submarginal macrochaetae, one about one quarter the distance along the margin and the other about seven-eighths along the margin associated with the posterior trichobothrial area. Anterior trichobothrium a little further than half way along the margin, with two to four setulae posterior to the trichobothrium, not associated with a macrochaeta ( Fig. 101 View Figures 99–108 ). The posterior trichobothrium mediad of a submarginal macrochaeta and its cilium, with two or three setulae posterior to this group ( Fig. 102 View Figures 99–108 ). Posterior margin with 1+1 single macrochaetae each associated with two cilia ( Fig. 103 View Figures 99–108 ). — Mesonotum ( Fig. 104 View Figures 99–108 ) also with small setae along the margins as well as three combs each of two macrochaetae anterior to the anterior trichobothrial area, both trichobothrial areas ( Fig. 105 View Figures 99–108 ) are more posterior than on the pronotum, the anterior trichobothrium located about 5/6 the distance along the margin and not associated with any macrochaeta and the posterior area as in the pronotum; 1+1 posterior macrochaetae as in pronotum. — Metanotum ( Figs 106, 107 View Figures 99–108 ) similar to mesonotum.
Presternum with transverse row of strong macrochaetae ( Fig. 108 View Figures 99–108 ) as well as some simple cilia. All thoracic sterna with hyaline scales. — Prothoracic sternum ( Fig. 108 View Figures 99–108 ) cordiform, slightly wider than long (L/ W 0.91), 1+1 irregular combs of eight to nine bifurcate macrochaetae running subparallel to the margin, as well as some marginal setae and cilia in distal one quarter, short posterior margin between combs straight. — Mesosternum ( Figs 109 View Figures 109–122 ) sub-parabolic, as long as wide at its base, (L/ W 1.01) with about eight macrochaetae forming an irregular submarginal row along the posterior quarter of the margin, short posterior margin between combs straight. — Metasternum ( Fig. 110 View Figures 109–122 ) wider than long (L/ W 0.74), apically a little truncate, 1+1 apical combs of about five macrochaetae, the distance between the combs 2.3 times the average length of each comb (range 2.1–2.6), lateral margins with a few simple setae and cilia only adjacent to the combs.
Legs ( Figs 108 View Figures 99–108 , 110, 111 View Figures 109–122 ) becoming progressively longer and more slender with the tibia of PII being 1.3 times longer than that of PI and the tibia of PIII being 1.8 times longer than that of PI, tibia L/W ratio of legs PI 2.9, PII 3.2, PIII 3.6; tarsi L/W ratio PI 5.3, PII 8.0, PIII 9.2. Precoxa of PI with lateral combs of four macrochaetae. — Coxa of PI ( Fig. 108 View Figures 99–108 ) without comb near the anterolateral corners, but many strong macrochaetae in approximately two rows along the external margin, becoming shorter distally; inner margin with five macrochaetae distally over the articulation and another seta subdistally near three long thin seta on the dorsal face. — Trochanter with small setae. — Femur ventrally with one large macrochaeta near the trochanter and three large bifurcate carrot-shaped macrochaetae plus two strong simple macrochaetae on the posterior bulge, distal anterior corner with two macrochaetae, lanceolate scales along the margin and extending onto the ventral face of the femur in the anterior half, rest of ventral surface with fine scattered setae. — Tibia with a few lanceolate scales on the ventral face proximally, rest of surface with setae, a strong carrot-shaped macrochaeta distally as well as a thinner pair subdistally, another pair midway along the margin and a smaller pair near the proximal end of the posterior margin, distal end of tibia with a row of stronger setae, anterior margin with two stout macrochaetae about one third and two thirds along the margin, as well as smaller setae; apical spine with several setae, some quite strong. — Tarsi of four articles, the basal tarsal article of PI not quite as long as the remaining articles together, bearing some stronger setae below and many other smaller setae over the surface; second and third articles the shortest, each with two stronger setae ventrally. Pretarsus with two long curved lateral claws and a shorter straight medial claw. PII ( Fig. 111 View Figures 109–122 ) similar to PI except coxae with fewer macrochaetae along the outer margin, only becoming two macrochaetae wide in the distal half, with about seven stout setae over the articulation, the tibia with three stout macrochaetae along the dorsal margin and the first tarsal article is longer than the remaining three together, and PIII ( Fig. 110 View Figures 109–122 ) similar to PII but areas of lanceolate scales more extensive.
Abdomen: Urotergite I with 2+2 combs, the lateral combs of two macrochaetae each associated with three marginal setae and a setula, the submedial combs with one or two marginal setae, 0–3 setulae and a cilium on the laterad end of each comb; urotergites II–VII ( Fig. 112 View Figures 109–122 ) with 3+3 small combs as shown in table 7, each lateral comb associated with 1–3 marginal setae, 1–3 setulae, usually a cilium at the mediad end of each comb and sometimes one between, and anterior to, the two most mediad macrochaetae, each sublateral comb with 0–2 marginal setae and 1–3 setulae, the submedial combs usually with a cilium on either side of the single macrochaeta and rarely a setula between the macrochaeta and the margin ( Figs 113–115 View Figures 109–122 ); urotergite VIII with 2+2 combs, lacking the sublateral comb; urotergite IX without combs but with two delicate marginal setae and two cilia in each infralateral corner ( Fig. 116 View Figures 109–122 ). Urotergite X ( Fig. 117 View Figures 109–122 ) short and distinctly trapezoidal (L/W about 0.35), with 1+1 macrochaetae in the posterolateral corners, each associated with cilia on each side and numerous setae along the margins.
Urosternite I with a medial comb of three macrochaetae and two setulae on a non-protruding region ( Figs 118, 119 View Figures 109–122 ), urosternite II–VI ( Figs 120, 121 View Figures 109–122 ) with 1+1 lateral combs each of four or five macrochaetae and two marginal setulae plus a cilium at the laterad end of each comb, the distance between each comb is about nine times the average length of the combs on the segment (range 8.7–10.2), urosternite VII ( Fig. 122 View Figures 109–122 ) with styli, 1+1 combs each of two macrochaetae located mediad of each stylus, associated with two marginal setulae, laterad of the stylus is a cilium associated with two marginal setulae. Urosternite VIII in ♀ divided into separate coxites shaped as shown in figure 123, each bearing a small stylus which is apically armed with some strong setae, one or two macrochaetae mediad of the stylus insertion associated with a few small marginal setae, with two or three setae and a cilium on the outer side of the stylus. Styli present in three pairs, those on IX about twice as long as those on VIII which are just a little longer than those on VII.
Coxite IX of ♀ ( Fig. 123 View Figures 123–126 ) with the internal process acute apically, about three times longer than the external process and 1.3 times as long as wide at its base, reaching to about one third the length of the stylus; external and internal margins of internal process and external margin with a few moderately strong setae, apex of outer process with three or four strong setae. — Ovipositor ( Fig. 123 View Figures 123–126 ) probably not yet fully developed as its only reaches the end of the styli (1.20 HW), composed of about 45 divisions (range 44–47). Distal divisions of gonapophyses difficult to see adequately in prepared material ( Fig. 124 View Figures 123–126 ) with only short fine setae and setulae.
Cerci ( Figs 125, 126 View Figures 123–126 ) with basal divisions as long as wide (or perhaps it is several divisions with indistinguishable sutures), divisions two to four shorter than wide, fifth division as long as wide consisting of two annuli and first lanceolate scales seen, following division s consisting of four annuli eventually increasing to eight annuli with the setae, macrochaetae and trichobothria becoming increasingly stronger and longer, lanceolate scales not visible in distal two thirds of cerci and not seen on median dorsal appendage.. — Median dorsal appendage ( Fig. 128 View Figures 127–136 ) similar.
Habitat. Collected on a remote rock pyramid, the remnant of an old volcanic cone.
Etymology. Named after the dramatic appearance of the island from which this species was collected.
Even though only a single subadult female specimen was available, the species is described as new because it has a clear morphological difference to the published description of its probable nearest neighbour ( H. rouxi from New Caledonia) and good molecular sequence data are available for it. Heterolepisma rouxi is in need of redescription as characters such as the chaetotaxy of the anterior margin of the frons, the position of the trichobothrial areas of the nota and the presence or absence of lanceolate scales were not reported. Heterolepisma heraldense sp. nov., described below, while distinct from H. pyramidum sp. nov., may eventually be shown to be conspecific with H. rouxi when the latter species is redescribed according to current criteria.
The character analysis places H. pyramidum sp. nov. in a clade with H. parvum , H. heraldense sp. nov. and H. serranoi which all have a glabrous anterior margin to the frons, lanceolate scales, a medial comb on urosternite I and sublateral combs on urosternites II-VII consisting of more than one macrochaeta. The limited molecular data available for H. parvum (28S of three specimens) and one specimen of H. pyramidum sp. nov. offers no support for this arrangement (see supplementary data on Figshare).
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