Machilinus petrophilus Kaplin, 2020

Kaplin, Vladimir & Martynov, Vladimir, 2020, Three new species of bristletails of the families Meinertellidae and Machilidae (Archaeognatha) from Ukraine and Southern Russia, Acta Entomologica Musei Nationalis Pragae 60 (2), pp. 463-474 : 464-467

Machilinus petrophilus Kaplin , sp. nov.

( Figs 1–3 )

Type material. HƟΓƟΤΥΡΕ: 3 (slide-mounted, ZIN), UKRAINE: Donetsk region, near Amvrosiivka, 47°47′45″N, 38°28′48″E, 165 m a.s.l., scree of lime marl, petrophytic steppe, under stones, September 24, 2019, V. Martynov leg. PΑ*©ΑΤΥΡΕ: ♀ (on slides), the same locality, V. Martynov leg. ( ZIN).

Description. Body length: male 6.6 mm, female 6.5 mm. Body width: male 1.9 mm, female 2.0 mm.Antennal length: male 4.8 mm, female 4.0 mm (broken); cercal length 1.8 mm in male, 2.6 mm in female; total eyes width: 0.89 mm in male, 0.88 mm in female; eye length: 0.53 mm in male, female 0.59 mm in female; paired ocelli width: male and female 0.16 mm in both sexes; paired ocelli length: 0.11 mm in both sexes. Ovipositor length: 3.2 mm. Thoracic coxal styli absent. Head including antennae, maxillary and labial palpi, clypeus, labrum, labium and legs without scales.

Sex

Leg articles Male Female fore 5.36–5.50 4.78–5.08 Tarsus middle 4.75–5.27 4.72–4.92 hind 6.03–6.38 5.95–6.05 fore 2.06 1.96 Tibia middle 2.37–2.58 2.00–2.46 hind 3.12–3.15 3.17–3.36 fore 1.96–2.00 1.93–1.94 Femur middle 2.49–2.76 2.69–2.84 hind 2.64–2.78 2.98–3.04 fore 2.68–2.70 2.20–2.23 Coxa middle 2.53–2.58 2.92–2.94 hind 2.88–2.92 2.95–3.09

General body color whitish, with hypodermal pigment. Antennal base, occiput, frons, gena, lateral sides of clypeus, labrum, labium, maxillae, mandibles, maxillary and labial palpi, antennae, legs, thorax, abdominal tergites and sternites with purple-brown hypodermal pigment of medium to high intensity. Color of body scales brown. Antennae of male and female shorter than body. Ratio of length to width of scapus about 2.2 in male and 1.9 in female ( Fig. 1A ). Distal chains of flagellum divided into 8–9 annuli in both sexes. Two or three distal chains of antennal flagellum broken. Clypeus of both sexes with relatively numerous short simple chaetae ( Fig. 1B ). Front half of female clypeus with numerous dark small chaetae. Cercus in male and female approximately 0.27 times and 0.40 times as long as body length, respectively.Apex of cercus with one large lateral spike ( Fig. 1C ). Second lateral spike smaller and broken. Each division of cercus with two or four rows of scales. Divisions of cerci, except for apical one, with one to three supporting spines on inner side.

Compound eyes bicolor light gray with brown speckles (in ethanol). Ratio of length to width of compound eye about 1.2 in male and 1.3 in female; ratio of contact line length to eye length 0.70 in male and 0.76 in female. Paired ocelli oval, sublateral, white, 1.5 times as wide as long in male and 1.4 times in female. Distance between inner margins of ocelli 0.68–0.70 and between their outer margins 0.96–0.98 of total width of compound eyes in both sexes ( Fig. 1B ).

Apical article of maxillary palpus in both sexes 0.56– 0.63 times as long as preceding one. Dorsal surface of 7 th, 6 th and 5 th articles of maxillary palpus with 10, 9 or 10, and 1 hyaline spines in male, and 10 or 11, 11 or 12, and 3 or 4 spines in female, respectively ( Fig. 1D ). 5 th article of maxillary palpus about 1.67 times as long as 4 th article in male and 1.45–1.50 times in female. Second article of male maxillary palpus noticeably curved with external lateral apical apophysis ( Fig. 1E ), but absent in female maxillary palpus. Apophysis far surpassing distal end of second article. Ventral part of apophysis and adjacent part of 2 nd article with about 12–15 dark, almost black, short spiniform chaetae (spines). 3 rd article of male maxillary palpus also with about 25 almost black short lateral spines ( Fig. 1E ). Dorsal and lateral surface of 1 st, 2 nd and 3 rd articles of male maxillary palpus with numerous relatively long thickened macrochaetae. Apical article of labial palpus triangularly oval, 3.8 times as long as wide in male and 3.2 times in female ( Figs 1 F–H). Apical article of male labial palpus without sexual dimorphism. Space occupied by distal connuli of third article of labial palpus well developed. Ratio of lengths of this space and apical article of labial palpus about 0.40–0.42. Distal part of mandibles with two teeth in both sexes ( Fig. 1I ).

Fore femur and tibia of male and female widened. Ratios of lengths to widths of coxa, femur, tibia and tarsus as shown in Table 1. Ratio of length of 3 rd tarsomere to total length of tarsus 0.36–0.37 in male and 0.40–0.41 in female ( Fig. 1J ). Legs of male without long thin chaetae. Ventral surface of femora, tibiae and tarsi with spines as shown in Table 2. Pretarsi with well-developed conical strongly pigmented support protrusion ( Fig. 1K ).

In both sexes, abdominal segments II–VII with 1 + 1 eversible vesicles ( Figs 2A, B ). Posterior angle of urosternites more than 130° ( Table 3). Ratios of lengths of urosternite, stylus (without apical spine) and urocoxites I–IX as shown in Table 3. Inner posterior lobes of urocoxites VII of female protruding ( Fig. 2C ); ratio of length to their total width about 0.39.

Pronotum as shown in Fig. 2D . Inner margins of its lateral expansions with about 20 + 20 macrochaetae in male and 11 + 11 in female. Lateral margins of mesonotum with 50–60 + 50–60, metanotum with 25–30 + 25–30 macrochaetae in both sexes. Lateral parts of mesonotum and sublateral parts of metanotum also with numerous long and thin chaetae in both sexes. Anterior part of urotergite I with 5–7 + 5–7 sublateral chaetae ( Fig. 2E ), urotergites II–X without chaetae in both sexes. Anterior part of urocoxites I with 7–9 + 7–9 chaetae in both sexes. Distribution of sublateral chaetae on urocoxites II–IX as shown in Table 4.

Ovipositor slender, elongate, extending much further than apex of styli IX. Anterior and posterior gonapophyses with 68 and 70 divisions, respectively ( Figs 3A, B ). Two basal divisions of anterior gonapophyses and about 29 proximal divisions of posterior gonapophyses glabrous.

Apical divisions of anterior and posterior gonapophyses with five or six chaetae (not counting sensory chaetae and apical spines) (Figs C, D). Distal divisions of anterior and posterior gonapophyses with long chaetae as shown in Figs 3A, B . Apical spines of gonapophyses as long as 2.6–3.0 apical divisions combined ( Figs 3C, D ).

Male genitalia without parameres. Penis does not significantly attain the apex of urocoxites IX ( Fig. 3E ). Ratio of lengths of apical and basal divisions of penis about 1.12.

Differential diagnosis. Machilinus petrophilus sp. nov. belongs to the subgenus Machilinus s. str. with 1 + 1 eversible vesicles on urocoxites II–VII, and urostyli with apical spines (SΤU*©Μ & BΑർ*ü ĐΕ RƟർΑ 1992). This subgenus inсludes 21 described species, one of them with 3 subspecies. The bristletails of this subgenus on the structure of the male maxillary palpus can be divided into 4 groups: “ rupestris ”, the 2 nd and 3 rd articles of male maxillary palpus without ventral spines ( Machilinus rupestris (Lucas, 1846) ; M. spinosus Bitsch, 1967 ; M. elharchai Bitsch, 1967 ; M. casasecai Bach, 1974 ; M. rosaliae Mendes, 1977 ; M. portosantensis Mendes, 1981 ; M. botellai Gaju-Ricart, Bach de Roca & Molero-Baltanas, 1992 ; M. costai Notario-Muñoz, Bach de Roca & Gaju-Ricart, 2000; M. caucasicus Kaplin, 2007 ; M. obscurus sp. nov.); “ kleinenbergi ”, the

3 rd article of the male maxillary palpus with ventral spines which are missing on the 2 nd article; “ rocai ”, the 2 nd and 3 rd articles of the male maxillary palpus with ventral spines ( M. rocai Bach-Piella, 1975 ); “ suttropi ”, the 2 nd article of the male maxillary palpus with ventral spines which are missing on the 3 rd article ( M. suttropi Sturm, 2002 ). The 2 nd group “ kleinenbergi ” includes 9 described species, which can be divided into two subgroups: “ helicopalpus ” ( M. cisatlanticus Janetschek, 1953 ; M. helicopalpus Janetschek, 1954 ; M. gredosi Bach, 1971 ; M. valencianicus Mendes & Bach de Roca, 1981 ) with a very apparent swelling on the ventral side of the maxillary palpus and “ bejarensis ” ( M. bejarensis Bach, 1971 ; M. kleinenbergi (Giardiana, 1900) , redescribed by MΕΝĐΕඌ et al. 1981; M. spinifrontis Bach de Roca, 1984 ) with the 2 nd article of the male maxillary palpus without the very apparent swelling on the ventral side (JΑΝΕΤඌർ*üΕΚ 1953, 1954; BΙΤඌർ*ü 1967; BΑർ*ü PΙΕΓΓΑ 1971, 1975; BΑർ*ü ĐΕ RƟർΑ 1974, 1984; MΕΝĐΕඌ 1977, 1981; MΕΝĐΕඌ & BΑർ*ü ĐΕ RƟർΑ 1981; GΑ*°U-RΙർΑ*©Τ et al. 1992; NƟΤΑ*©ΙƟ-MUŇƟƶ et al. 2000; SΤU*©Μ 2002; KΑΡΓΙΝ 2007). The new species with black, relatively short and strong spines on the 3 rd and 2 nd articles of the male maxillary palpus are closest to M. rocai .

Other species with these spines on the 3 rd and 2 nd articles of the male maxillary palpus are not described in the genus Machilinus . Distal chains of flagellum are divided into 8–9 annuli in Machilinus petrophilus sp. nov. and into 8 annuli in M. rocai . The main morphological differences between M. petrophilus sp. nov. and M. rocai are as follows. The color of compound eyes is uniform in M. rocai , and light gray with brown speckles in M. petrophilus sp. nov. Ratio of length to width of compound eye is 1.3–1.4 in M. petrophilus sp. nov. and 0.9–1.0 in M. rocai . Paired ocelli are 1.5 times as wide as long in male and 1.4 times in female of M. petrophilus sp. nov., and about 3.0 times in male of M. rocai . Clypeus of the male and female of M. petrophilus sp. nov. bears numerous short chaetae that are missing from the clypeus of both sexes of M. rocai . The lateral apophysis of the 2 nd article of the male maxillary palpus reaches far beyond the top of this article in M. petrophilus sp. nov., but it does not significantly reach the top of the 2 nd article of the male maxillary palpus in M. rocai . Number of spines on the hind tibia of M. petrophilus sp. nov. and M. rocai is 24–25 in male and 21 in female, and 22 in male and 11 in female, respectively. Apical article of male labial palpus is without sexual dimorphism in M. petrophilus sp. nov. and with it in M. rocai .

Etymology. The species name petrophilus is a latinized Greek adjective meaning “loving petrophytic deposits,” referring to the predominant habitat type ( Fig. 8 ).

Habitats. Scree of lime marl on the slope of the ravine.

Petrophytic steppe communities with dominance of Thymus cretaceus Klokov & Des. -Shost., Artemisia hololeuca M. Bieb. ex Besser , Onosma tanaitica Klokov , Linum czernjavii Klokov , Koeleria gracilis Pers. , and Jurinea brachycephala Klokov ( Fig. 8 ).

Figures

Fig. 1. Machilinus petrophilus sp. nov. (B, D, E, G–K – male, holotype; A, C, F – female, paratype): A – scapus and pedicellus of antenna; B – head, frontal view; C – distal part of cercus; D – maxillary palpus; E – 1st–3rd articles of maxillary palpus; F, G – labial palpus and labium (part); H – apical article of labial palpus; I – distal part of mandible; J – part of hind leg; K – pretarsus of hind leg. Scale bar: 0.1 mm.

Fig. 2. Machilinus petrophilus sp. nov. (A, D – male, holotype; B, C, E – female, paratype): A, B – urosternite and urocoxites V (part); C – urosternite and urocoxites VII (part); D – pronotum (part); E – urotergite I (part). Scale bar: 0.1 mm.

Fig.3. Machilinus petrophilus sp. nov.(E – male, holotype;A–D – female, paratype):A – urocoxite VIII, with anterior gonapophyses; B – urocoxite IX, with posterior gonapophyses;C – distal part of anterior gonapophysis; D – distal part of posterior gonapophysis; E – urocoxite IX, with penis. Scale bar: 0.1 mm.

Figs 8–9. Habitats of the new species. 8 – habitat of Machilinus petrophilus sp. nov., Amvrosiivka, July 22, 2019. 9 – habitat of Machilinus obscurus sp. nov., Starobeshevo, right bank of the Kalmius river, September 24, 2019. (Photos by V. Martynov).