Cordulegaster vanbrinkae, Lohmann, 1993

HoluŠa, Otakar, 2022, Description of the last instar larva of Cordulegaster vanbrinkae and emergence place from northern Iran (Odonata: Cordulegastridae), International Journal of Odonatology 25, pp. 72-79 : 73-76

Description of the last instar larva of Cordulegaster vanbrinkae

Measurement section

Total length of larvae 34.0– 39.3 mm (see Table 1), head width 7.20 – 8.10 mm,length of hind femur 4.2 –5.85 mm.

General. Color basically brown, head and prothorax dark brown without any paler spots ( Figs 1–3 ), two indistinct darker longitudinal stripes on the dorsal part of sternites ( Fig. 3 ). Body surface without gloss, rather rough with fine pale brown hairs, longer hairs at posterior edge of thorax, also on side of sternites and legs.

Head. Squarish, anteclypeus and postclypeus brown in color, anterior margin of frons with row of short hairs, interior parts of compound eyes dark brown. Antennae filiform, 7-segmented, length 7.7–8.5 mm, ratio antennae segments (S1/S1+S5)0.96. Base of antennae with small pale spots. Prementum: length 5.8–7.3 mm (x = 6.3 mm ♂, 6.9 mm ♀), maximal width (W+) 5.9–6.8 mm (x = 5.8 mm ♂, 6.3 mm ♀), minimal width (W-) 1.7– 2.6 mm (x = 2.1 mm ♂, 2.2 mm ♀), with ratio length/ maximal width of prementum 0.96–1.14. Anterior margin of ligula (median lobe of prementum) with usual pair of V-shaped apical black outgrowths ( Fig. 4C ). Interior margins of palpal lobes with irregularly dentation: 3 large teeth at lef lobe, 2 large at right lobe, every tooth with additional small 2–4 small teeth ( Fig. 4B ). Apex of all teeth black-brown. Movable hooks long and rather stout, with black apex. Lobes with 5 palpal setae. Prementum on each side at the centre with 5 long premental setae, and one to three shorter setae situated more medially ( Fig. 4A ).

Thorax. Prothorax broad with broadly rounded edges, only slightly narrower than head, ratio head/prothorax width 1.14–1.18 (see Table 1). Synthorax as wide as head. Wing sheaths parallel, anterior margin of forewings reach to the middle of 4 th sternite, and hindwing reach to the posterior edge of 4 th sternite. Edge and sides of thorax with long pale brown hair.

Abdomen. Brown without any paler stripes, on dorsal parts with inconspicuous dark longitudinal stripes. Hind margins of segments S1 to S9 with row of pale brown hair. Row of longer pale brown hairs also on lateral edges of sternites, especially around lateral sternite edge at S6–9. Dorsal spines absent. Lateral spines at 8 th sternite absent, lateral spines at S9 sternite very small, length 0.1 to 0.3 mm (x = 0.18 mm), normally invisible due to hairs at lateral sternite edge ( Fig. 3 ). Epiproct approximately as long as paraprocts and slightly bent ventrally at their tips, cone shaped anal pyramid, without significant bend at ends from lateral view ( Fig. 3 ). Ratio of length to width of base of paraprocts 0.91–1.27. Epiproct surface brown and with short pale brown hairs. Ovipositor closely S9 tergit reaches anterior margin of S10 ( Fig. 3A ). Ratio cerci /10 th segment 1.35–2.08.

Comparative analysis

In the western Palaearctic the genus Cordulegaster includes species divided into the two species-groups, the “ boltonii -” and “ bidentata -“group ( Verschuren, 1989; Boudot, 2001), recently also coronata -group (Schnei- der at al., 2021). C. vanbrinkae is morphologically similar to C. heros and C. picta , with which it forms the eastern species subgroup of the boltonii -group. Typical for this group is the conical end of the anal pyramid without a hooked ends of the paraprocts. The ratio of the length of the cerci to the length of 10 th segment is for all species 1.35–2.33, and also, the number of the long palpal setae is same ( Table 2). All species of the eastern subgroup have same feature: small lateral spines at segment 9, which reaches maximal one third of sternite 9. Cordulegaster heros differs from C. van- brinkae and C. picta by the presence of lateral spines on segment 8 ( Table 2) which in C. vanbrinkae is al- ways missing. Similarly, the lateral spine on segment 9 of C. vanbrinkae is very small and hardly visible because it is covered by a clump of long hairs. The ratio of the length of the lateral spine on segment 9 to the length of segment 9 is 0.05–0.15, whereas in C. picta this ratio is slightly higher (0.12–0.22). The prementum of C. vanbrinkae is slender as revealed by the ratio of length to maximal width between 0.96 and 1.14, and C. vanbrinkae differs clearly from C. picta by the low number of long premental setae—(5, rarely 6 vs 6, rarely 7) and the short premental setae (1–3 vs 3–4) ( Table 2).

A

Emergence places—exuviae

A total of 49 exuviae were found (several exuviae were in varying degrees of damage–the abdomen or head were missing). The place of emergence was evaluated with respect to their location, i.e. it was the place where the image was hatched: a) rock walls and boulders, b) leaves or stems of plants (e.g. Hedera helix , Rubus sp. ), c) tree trunks ( Fig. 5 ). The “offer” of these emergence places is based on the character of the habitat that species inhabits, which are watercourses shaded with rich vegetation and tree layer, riverbeds are rocky, sometimes even canyoned with rock walls and boulders (cf. HoluŠa et al., 2015). Rock walls and boulders dominated as a type of emergence place (57%, Figs 5 , 6 , 7 ), then site type —plant leaves (27%, Figure 8 ) and last one—tree trunks (16%). Even the bases of large boulders, which formed rocky “overhangs”, were selected by larvae for emergence ( Fig. 9). It is obvious that the larva at the end of its “journey” climbed as if on the ceiling of a rock niche or overhang.

Emergence places were at different distances from the shoreline and at different heights—female exuviae occurred at a distance from 0 to 310 cm (x = 65 cm) at a height above the ground from 10–265 cm (x = 145 cm), the total distance larval movement was from 40 to 475 cm (x = 198 cm) ( Fig. 7 ). Male exuviae were found at a distance from 0 to 215 cm (x = 70 cm), at an altitude of 20–175 cm (x = 125 cm), the total distance of the larva’s movement was from 20 to 375 cm (x = 200 cm).

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cm

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ground

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Height

Distance from shore (cm)

Figures

Figure 1. Last instar of larva of Cordulegaster vanbrinkae Lohmann, 1993—female.

Figure 3. The top of female abdomen and anal pyramid of larva of Cordulegaster vanbrinkae Lohmann, 1993, A – lateral view, B – dorsal view.

Figure 4. The labium of larva of Cordulegaster vanbrinkae Lohmann, 1993, A – dorsal view, B – frontal view to palpal lobes, C – anterior margin of ligula; Scale bars = 1 mm.

Figure 5. Cordulegaster vanbrinkae Lohmann, 1993—position of exuviae in riparian parts of the habitat. x-axes: (-) lef bank, (+) right bank.

Figure 6. Proportion of different types of emergence place of Cordulegaster vanbrinkae Lohmann, 1993.

Figure 7. Variability of position of exuviae by sex of Cordulegaster vanbrinkae Lohmann, 1993 (distance from shore, height above ground, total distance; all in cm).

Figures 8. Exuviae of Cordulegaster vanbrinkae Lohmann, 1993 on vegetation in forest undergrowth (1st exuvia at the lef edge of picture, 2nd in middle part), locality in Northern Iran, Gīlān provincy, Fouman—Qaleh Rudkhan, 9.VII.2014 (photo by Otakar HoluŠa).