Ctenolepisma (Ctenolepisma) udumalpetense, Hazra & Jana & Mandal & Molero-Baltanás, 2022

Hazra, Ashis Kumar, Jana, Debanjan, Mandal, Guru Pada & Molero-Baltanás, Rafael, 2022, On two new species of the genus Ctenolepisma (Zygentoma: Lepismatidae) from India, Zootaxa 5222 (1), pp. 59-68 : 64-67

Ctenolepisma (Ctenolepisma) udumalpetense sp. n.

( Figures 18−38 )

Type material. Holotype: Forest floor beside Trimurti dam, Udumalpet, Tiruppur district, Tamil Nadu, India (10°29’11” N and 77°9’46” E), 17.ix.2019, 1 female, coll. A.K. Hazra, Registration number 3053/H14, Zoological Survey of India, Kolkata . Paratypes: Same locality as holotype, 18.ix.2019, 22 (12 males 10 females), coll. A.K. Hazra, Registration number 3054/H14, Zoological Survey of India, Kolkata .

Etymology. The species is named after the name of the locality Udumalpet, Tiruppur district, Tamil Nadu, India, which is the type locality.

Diagnosis. This new species is a relatively small Ctenolepisma s. str. (about 6 mm long) with five sensory papillae on the apical articles of their labial palps. Their trichobothrial areas are arranged as in C. ciliatum . It has 1+1 bristle-combs of macrosetae in each thoracic sternite, 3+3 bristle-combs in urotergites II-VI, trapezoidal urotergite X and two pairs of abdominal styli. Ovipositor short, with less than 30 divisions. As in related species, tibial scales are absent, but femoral scales are narrower than usual (not widely rounded, but ovoid or elliptical).

Description. Body length of females up to 6.1 mm, males slightly shorter (5.8 mm). Habitus ( Fig. 18 ) fusiform, with the thorax slightly wider (1.19 mm) than the abdomen base (1 mm). Body pigment dark, uniformly distributed; antennae with evenly distributed light pigmentation but terminal filaments show distinct light and dark annulations. Scales dorsally dark brown. Ventral scales lighter pigmented. Body scales are rounded, fan-shaped and ovoid ( Fig. 19 ) Macrosetae bifid, plumose; chaetotaxy of head as usual for the genus. Both clypeus and labrum with numerous bifid and pectinate macrosetae. Clypeus with two tufts of setae, each composed of 32–34 macrosetae. In the middle of the clypeus, a tuft of smooth hair-like setae present composed of 14 setae ( Fig. 20 ). Eyes black, composed of 12 ommatidia.

Antennal length up to 4 mm, shorter than body, surpassing the thorax up to abdominal segment six when directed backwards. Apical article of maxillary palp ( Fig. 21 ) slightly longer (0.34 mm) than the penultimate (0.31 mm). Apical article of the labial palp about as wide (0.24 mm) as long (0.23 mm), with 5 distinct ovoid sensory papillae arranged in a compact single row ( Figs. 22, 23 ).

Medial part of the pronotal collar ( Fig. 24 ) composed of 3–4 rows of macrosetae, lateral regions each with a single row of smooth macrosetae. Lateral margins of pronotum ( Fig. 25 ) with 6+5 combs composed of 1–3 macrosetae each, including two trichobothrial areas, one in the inner side of the last comb (N) and another in the inner side of the N-3 comb. Mesonotum ( Fig. 26 ) lateral margins with 8+8 combs consisting of 1–3 macrosetae; only one trichobothrial area in the outer side of the N-1 comb observed. Metanotum ( Fig. 27 ) lateral margins with 6+6 combs composed of 1–3 macrosetae; trichobothria not seen. Hind borders of pro-, meso- and metanota with 1+1 bristle combs composed of 1–2 macrosetae each.

Thoracic sternites as in Figs. 28–30 . Prosternum 0.65 mm long, its length/width ratio about 0.9, with rounded posterior apex; postero-lateral margin with 1+1 bristle combs, each composed of 3–4 macrosetae. Mesosternum 0.84 mm long, its length/width ratio about 1.1, slightly wider than prosternum; its posterior apex rounded with 1+1 bristle combs, each composed of 3 macrosetae. Metasternum 0.82 mm long, its length/width ratio about 0.9; with broadly rounded apex, with 1+1 bristle combs, each composed of 5 macrosetae; the distance between these combs about 5 times the width of a comb.

Scales present on coxae and femora ( Figs. 31 and 32 ); femoral scales (Fig.–33) smaller than coxal ones, elliptical and with rounded apical margin. Length/width ratio of protibia about 2.4; of mesotibia about 2.5 and of metatibia about 2.8. Two macrosetae present in the dorsal margin of the protibia and three macrosetae in the ventral margin; mesotibia with two dorsal and five ventral macrosetae; metatibia with one dorsal and four ventral macrosetae. Protarsal tarsomere lengths I‒IV 0.25 0.09 mm 0.12 0.1 mm, respectively. The length of tarsomeres I, II, III and IV (in mm) on mesotarsus as follows: 0.34, 0.08, 0.12, 0.1 mm. The length of tarsomeres I, II, III and IV (in mm) on metatarsus as follows: 0.48, 0.11, 0.13, 0.12.

Urotergite I with 1+1 bristle-combs composed of 3 macrosetae. Urotergites II–VI with 3+3 bristle-combs composed of 2‒5 macrosetae, urotergites VII‒VIII with 2+2 bristle-combs composed of 3‒4 macrosetae. Urotergite X trapezoidal, wider than long at its base (length 0.48 mm, base width 0.99 mm, apical width 0.29 mm), ratio length/ width about 0.48, posterior margin slightly concave ( Fig. 34 ), with 1+1 bristle-combs of 3–4 macrosetae each.

Urosternites I and II without setae, III–VIII with 1+1 lateral bristle-combs with 4–6 macrosetae. The width of the bristle combs and the space between them varying on each urosternite; this distance ranging from 10 times the width of a comb on urosternite VII to about 17 times on urosternite III. On urosternite IV ( Fig. 35 ) this ratio about 13.

Both sexes with two pairs of styli on urosternites VIII and IX. Styli IX 2.3 times longer than the inner process of the corresponding coxite in males and 2.1 times longer in females. In females, the length of styli VIII 6.2 times longer than their width, and length of styli IX about 8.7 times longer than wide. Ratio of the length of styli IX/ length of styli VIII is 1.2–1.5 for females and 1.3–1.5 for males. Inner process of female coxite VIII obliquely rounded. Length of inner process of coxite IX twice its width at its base and 4 times longer than the outer process. Ovipositor short, not surpassing the tip of coxite IX ( Fig. 36 ). Anterior gonapophysis with 29 divisions, bearing 2–3 small setae at the apex. Posterior gonapophysis with 27 divisions. Penis as in Figures 37 and 38 .

Distribution and habitat. Specimens of Ctenolepisma udumalpetense sp. n. were found in large numbers generally in shady semi-decomposed dry leaf litter in forested regions. It is an active insect on the ground in leaf litter beside Trimurti Dam. The species is abundant in this tropical semi- evergreen forest of the Southern part of India. The protection of this habitat will help to conserve this Zygentoma species.

Differential diagnosis. C. udumalpetense sp. n. is probably related to species of the subgenus Ctenolepisma s. str. with trapezoidal tenth urotergite, 3+3 bristle-combs in urotergites II-VI and two pairs of abdominal styli, such as Ctenolepisma (C.) ciliatum (Dufour, 1831) or C. (C). longicaudatum Escherich, 1905 . Apart from these two species, some others have been described that share the aforementioned characters: C. (C.) iranicum Molero, Kahrarian & Gaju, 2016 , C. (C.) armeniacum Molero-Baltanás, Gaju-Ricart, Bach de Roca & Mendes, 2010 and C. (C.) abyssinicum Mendes, 1982 from Iran, Armenia and Ethiopia, respectively. All of these species also possess on the apical article of the labial palp five strong ovoid sensory papillae arranged in a single row ( Figs 22–23 ). They differ from C. udumalpetense sp. n., in the following characters:

1. The prosternum of C. udumalpetense sp. n. has a more rounded apex and only 1+1 pairs of bristle-combs ( Fig. 28 ). Macrosetae of these combs are, as well as those of meso- and metasternum, arranged in a single row. However, related species have at least 2+2 bristle-combs in the prosternum (frequently, 3+3 or more); moreover, the apex of this sternite in C. ciliatum and C. abyssinicum is more acute and the combs of thoracic sternites of C. armeniacum and C. iranicum are double (consist of at least two rows of macrosetae).

2. Ctenolepisma udumalpetense sp. n. has a maximum body length of 6.1 mm, whereas similar species typically reach 8 mm or more.

3. The ovipositor of C. udumalpetense sp. n. is relatively short, not surpassing the tip of the inner process of coxites IX. In the other related species mentioned babove, the ovipositor not only surpasses the apex of coxite IX but also the tip of the styli IX. The number of divisions is also higher in these previously known species (35- 49 in C. ciliatum , even more in other species), while the new Indian species has 29 divisions. This character and the smaller size could correspond to young silverfish, but no specimens of C. udumalpetense sp. n. have been found with a greater size or a longer ovipositor.

4. The femoral scales of C. ciliatum , C. armeniacum and C. iranicum are rounded, while in C. udumalpetense sp. n. are narrower, more or less elliptical ( Figs. 31–32 ). This character has not been described in the remaining species.

Figures

FIGURES 18–23. Ctenolepisma (Ctenolepisma) udumalpetense sp. n. 18) Female, dorsal habitus. 19) Body scales. 20) Head chaetotaxy with clypeus and labrum. 21) Male, maxillary palp. 22) Male, labial palp with sensory papillae. 23) Female, SEM photos of labial palp showing the sensory papillae arrangement. Scales: Fig. 18, 1 mm; Fig. 19, 10 µm; Figs. 20 and 21, 0.1 mm; Fig. 22, 50 µm; Fig. 23, 20 µm.

FIGURES 24–30. Ctenolepisma (Ctenolepisma) udumalpetense sp. n., female. 24) Pronotal collar showing row of macrosetae. 25) Pronotum, left half.26) Mesonotum, left half. 27) Metanotum, left half. 28) Prosternum.29) Mesosternum. 30) Metasternum. Scales: 0.1 mm.

FIGURES 31–38. Ctenolepisma (Ctenolepisma) udumalpetense sp. n. 31) Male, hind leg showing scales and setae of femur. 32) SEM photo showing the covering of scales and setae of femur. 33) Femoral scale of hind leg. 34) Female, urotergite X. 35) Urosternite IV. 36) Urosternite VIII and coxite IX with ovipositor. 37) Coxite IX with penis. 38) SEM photo of penis. Scales: Fig. 31, 50 µm; Fig. 32, 30 µm; Figs. 33 and 38, 20 µm; Figs. 34–37, 0.1 mm.