Cordulegaster kalkmani, Schneider, Vierstraete, Muller, van Pelt, Caspers, Ikemeyer, Snegovaya & Dumont, 2021, Schneider, Vierstraete, Muller, van Pelt, Caspers, Ikemeyer, Snegovaya & Dumont, 2021

Müller, Ole, Schneider, Thomas, Ikemeyer, Dietmar & Brochard, Christophe, 2023, Description of last instar larva of Cordulegaster kalkmani (Odonata: Cordulegastridae), International Journal of Odonatology 26, pp. 108-113 : 109-113

Description of the larva

General. The larva of C. kalkmani has the typical appearance of cordulegastrid larvae ( Fig. 1 ). The total length of the female exuvia is about 47 mm, the color of the body is brown, with no distinct color patterns, the entire body is covered with fine hairs, between the hairs, sediment particles from the habitat adhere to the body. Longer hairs and setae are present at the posterior edge of thorax, abdominal tergites, anterior border of sternites and legs.

Head. Nearly rectangular in dorsal view ( Fig. 2A ), maximum width about 8 mm, clypeus brown in color, anterior margin of frons with a row of short hairs, compound eyes large, forming antero-lateral angles, interior parts of compound eyes dark brown, segments 5–7 of both antennae are missing in the specimen, length of antennae segments ( AS 1 = 0.31; AS 2 = 0.69; AS 3 = 0.33; AS 4 = 0.38 mm).

The labium has the general shape of a cordulegastrid ( Figs 2B, C, E ). Prementum elongated. Length: width ratio of prementum 6.23: 5.93 = 1.05. Anterior margin of ligula with a row of dense and very short setae, in medial view with two humped protuberances slightly different in shape ( Fig. 2D ). The lateral margins of prementum with a row of short, regularly arranged setae. The mesial margins of palpal lobes with prominent irregularly pointed teeth ( Figs 2B, C, E ). Tips of all teeth strongly sclerotized, indicated by a strong brown color. Moveable hooks long and stout with dark brown apex. Prementum in dorsal view with five long setae at the right side, and four short setae medially placed, parts of the lef side are missing ( Fig. 2E , gray-shaded area). Palpal lobes with five palpal setae, outer margins of palpal lobes with two rows of dense setae (details Fig. 2E ).

Thorax. Wing cases nearly parallel, forewings 10.3 mm, hindwings 9.3 mm, sparsely setosed. The anterior margin of forewings extending up to the posterior margin of S3, margin of hindwings almost extends to the anterior margin of S4 ( Fig. 1 ). All legs with rows of setae interrupted by bare areas. Hindlegs extending to 7 th abdominal segment, all tarsi with long curved claws, tarsal formula: 3–3–3 ( Figs 1 , 3B ).

Abdomen. The abdomen is enlarged in the middle ( Figs 3A, D ), maximum width on S5; all tergites with very short setae beside some single longer setae, lateral margins of abdominal segments with rows of some longer setae, no dorsal spines at all ( Fig. 3F ), posterolateral spines at S9 ( Figs 3D, E ), only a hump-shaped lateral protuberance on S8, hidden between setae of segment’s margin.

The caudal appendages form a cone shaped pyramid in dorsal view ( Figs 3A, C ). Epiproct ( 2.49 mm) approximately as long as paraprocts ( 2.57 mm), cerci ( 0.89 mm) are less than half as long as epi- and paraprocts. In lateral view, the paraprocts curve slightly ventrally ( Fig. 3F ).

The ovipositor at S9 curved in a crescent shape does not reach S10, maximum length 2.36 mm ( Figs 3D, F ).

Habitat

In Bitlis province C. kalkmani was found at three localities ( Schneider et al., 2022). In the mountainous region south of the highway D 300 ( Van Bitlis Yolu) between the Kuskunkiran tunnel at the Bitlis-Van border and westward to Güntepe there are a number of brooks. These brooks feed a stream which runs parallel to the highway and flows near Güntepe into the Kesan River. The brook, where the exuvia was found ( Fig. 4 ), is 70– 110 cm broad and about 10–40 cm deep with a stony streambed without submerged vegetation but partially shaded by bushes and trees ( Salix spec. ). Its flow velocity was about 2–3 km /h. Sections with ripples alternated with low-flow calm water with sandy sediments or detritus. Pools caused by larger stones created a mosaic with variable flow conditions and substrate patches. The habitat is shown in Figure 4 .

Discussion and conclusions

Cordulegaster kalkmani is a recently described Western Palaearctic Cordulegaster species ( Schneider et al., 2021, 2022). It belongs to the ” boltonii group” and is the only member of this group in the Western Armenian Highlands ( Schneider et al., 2022). The exuviae of C. picta ( pictus) and C. heros were already described by Verschuren (1989), the exuvia of C. vanbrinkae was first described by Seidenbusch et al. (2015) and then again together with the larvae by Holuša (2022). The exuvia of C. kalkmani is described here for the first time and is compared to the other eastern members of the West Palaearctic “ boltonii goup”. In the region where the exuvia was found no other member of the “ boltonii group” occurs ( Schneider et al., 2021, 2022).

The rather slender and elongated prementum, and five or fewer premental setae is in line with the eastern members of the boltonii clade-(group) already recognized by Verschuren (1989). Seidenbusch et al. (2015) worked out several differential criteria in the morphology of exuviae between C. vanbrinkae and C. picta , for example, shorter epiproct and paraprocts in comparison with length of mentum, length of supraanalis and length of tergite 10 and sternite 10. Cordulegaster kalkmani clearly fits within the proportions of the other three species of this group. All the species show the same number of palpal setae: five. On the prementum C. picta mostly has six long premental setae while the other species have five (rarely six in C. vanbrinkae ). The number of short premental setae varies among different species and within the same species. Cordulegaster heros and C. vanbrinkae have no more than three short premental setae, C. picta vary between three and four and C. kalkmani has four. On the abdomen, C. heros has lateral spines on S8, C. picta shows variation in this criterion whereas C. vanbrinkae has no lateral spine on S8. The exuvia of C. kalkmani doesn’t have lateral spines on segment 8. Cordulegaster heros has stronger lateral spines on segment 9 than C. kalkmani , C. picta , and C. vanbrinkae .

Holuša (2022) compares the length of the cerci in relation to the length of S10. His data suggest that cerci are longer than S 10 in all compared species. However, examination of his figure of C. vanbrinkae , does not support this view. Furthermore, our own data of exuviae of C. vanbrinkae and the published data by Seidenbusch et al. (2015) do not support either this assumption. Indeed, the cerci of exuviae of C. vanbrinkae are shorter than S10.

Using our morphological data plus credible published characters a first attempt of a dichotomic key that summarizes the main differences between these four species is made. As already stressed, with only one exuvia of C. kalkmani it is not possible to confirm intraspecific morphological differences.

Figures

Figure 1. Reconstruction of the last instar of a female larva of Cordulegaster kalkmani. Drawing OM

Figure 2. Head of larva of Cordulegaster kalkmani. A – head, dorsal view (dotted lines indicate missing antennae segments); B – head, frontal view; C – labium, ventral view; D – anterior margin of ligula in ventral view; E – labium, dorsal view (missing structures indicated with gray-shaded area). Drawing OM

Figure 3. Details of the abdomen and the thorax of the larva of Cordulegaster kalkmani. A – abdomen, dorsal view; B – tarsus, hindleg; C – anal pyramid, dorsal view; D – abdomen, ventral view; E – details of lateral spines or protuberances, lateral view; F – abdomen lateral view. Drawing OM

Figure 4. Habitat of Cordulegaster kalkmani where the exuvia was collected. Two sections of the same brook are shown, 38°21’47.9’’ N, 42°45’36.7’’ E, 1,988 m a.s.l., East Turkey, Bitlis province.