Heteragrion azulum Dunkle, 1989

Novelo-Gutiérrez, Rodolfo & Gómez-Anaya, José Antonio, 2023, The rediscovery of Heteragrion azulum Dunkle, 1989 with additional notes on the female (Odonata: Heteragrionidae), Zootaxa 5256 (2), pp. 195-200 : 196-200

Heteragrion azulum Dunkle, 1989

Figs. 1–3 , 4a

Material. 6 ♁♁, 2♀♀. MEXICO. Veracruz State; Municipality of Catemaco, Km 7.1 road Tebanca-Miguel Hidalgo, stream at 402 m asl, 18°15.349 N, 94°57.516 W, 20 August 2022, R. Novelo, J.A. Gómez leg. ; 5♁♁; same data but 4 October 2022 ; 2 ♀♀; 1♁ same data but 5 October 2022 .

Redescription

Female ( Fig. 1a ). Head: Labrum and clypeus solid black metallic, frons grayish-violet, mandibles base grayishblue, genae pale violet ( Fig. 2a ). Clypeus and frons right-angled in profile view, but clypeal angle rounded. Vertex black, occiput mostly violet ( Fig. 2b ). Rear of head, maxillae, and labium creamy pale.

Thorax: Anterior lobe of pronotum mostly pale, with anterior margin black; middle lobe creamy pale; posterior lobe black with a small, triangular spot at sides, its posterior margin evenly arcuate ( Fig. 2b ); intersternite straight, without a recurved carina, a little higher and broader than setifer ( Fig. 2c ). Middorsal carina and antealar crest and sinuses black ( Fig. 2d ). Mesepisternum mostly grayish-blue with a 0.5 mm wide black stripe ( Fig. 1a ). Mesepimeron with a 0.5 mm wide dark brown stripe just posterior to humeral suture, this stripe extends onto mesekatepisternum but thinner ( Fig. 1a ). Remainder of pterothorax grayish-blue. Coxa and trochanter grayish-blue ( Fig. 2b ), femur and tibia light brown, tarsi and spurs black. All wings with two postquadrangular cells, pterostigmata reddish-brown ( Fig. 1a ).

Abdomen: S1 grayish-blue; S2–7 black dorsally, pale at sides, with posterobasal dark strikes on S3–6 ( Fig. 1a ); S8 mostly yellow with a dark, large, triangular spot along the middorsal full-length; S9 yellow with a thin, brown, longitudinal stripe to each side of midline on the basal 0.66; S10 yellow with a dark, triangular spot along the middorsal full-length ( Fig. 3a ). Cerci ( Fig. 3 ) convex dorsally, flattened ventrally, elongate, yellowish-brown on basal half, dark brown on distal half, with abundant, small, dark brown spines and short stiff setae. Gonapophyses ( Figs. 3b–c ) scarcely surpassing posterior margin of S10, lateral valvae light yellow, with the ventral margin convex bearing a row of 14–16 strong, dark, downcurved spines, gonostyli dark brown ( Fig. 3b ); ventral valvae dark reddishbrown, in ventral view as shown in Fig. 3c .

Measurements (in mm) [N=2]: TL 43.1–45.8, AL 35.0–37.5, FW 27.5–27.7, HW 27.3–28.0, Ce 0.7–0.9.

Remarks. The females we collected are larger in all the rank of measurements than those described by Dunkle (1993).

Diagnosis. Dunkle (1993) made a very complete description and diagnosis of the female of H. azulum comparing it with females of other Mexican species. Unfortunately, he did not provide any illustration at all. Here, we give an illustrated diagnosis of the female of H. azulum as follows (features of the other Mexican species in square brackets): two postquadrangular cells [three, H. tricellulare ]; labrum metallic black ( Fig. 4a ) [tan in H. albifrons ( Fig. 4b ), brown with a yellow central spot in H. alienum and H. tricellulare ( Figs. 4c and 4d , respectively]; pale colors in head and thorax grayish-blue [pale colors yellow in the other species]; intersternite straight, without recurved carina ( Fig. 2c ) [with recurved carina in all other species ( Figs. 5a–c )]; antealar crest and sinuses completely black ( Fig. 2c ) [with a large pale spot to each side in all other species ( Figs. 5d–f )]; dorsum of S2–7 black, pale at sides ( Fig. 1a ) [reddish-brown, slightly paler at sides in the other species]; S8 yellow with a dark, large, triangular spot ( Fig. 3a ) [S8 reddish-brown with a black, longitudinal, middorsal line in H. albifrons ( Fig. 5g ) and H. alienum , wider at base in this last species ( Fig. 5h ), yellow with an irregular, brown spot and a black middorsal line in H. tricellulare ( Fig. 5i )]; S9 yellow with a brown, longitudinal stripe to each side of midline ( Fig. 3a ) [S9 reddish-yellow more or less concolorous in H. albifrons ( Fig. 5g ); brown dorsally, yellow at sides in H. alienum ( Fig. 5h ); light yellow, unmarked in H. tricellulare ( Fig. 5i )]; S10 yellow with a dark, triangular spot at middorsal full-length ( Fig. 3a ) [S10 yellowish-brown with a thin, middorsal, dark line in H. albifrons ( Fig. 5g ), reddish-yellow in H. alienum ( Fig. 5h ), yellow in H. tricellulare ( Fig. 5i )].

Additional notes for males of H. azulum ( Figs. 1b , 3d–e ). The male specimens we collected agree well with the Dunkle’s description of the holotype ( Dunkle 1989). All males have the antealar crest and sinuses totally black. Here we provide some additional measurements (in mm) (N=6) [averages in brackets]: TL 49–53 [50.2], AL 40.1– 44.0 [41.9], FW 27.2–30.0 [28.3], HW 26.9–29.7 [28], Ce 1.0–1.1 [1.0]. Some high-quality photos of the male’s morphology are given too ( Figs. 1b and 3d–e ).

Habitat. Adults of H. azulum were found in a probably 3 rd order rocky stream, with a good coverage of riparian vegetation, although the adjacent areas have been altered for pasture lands. Individuals were collected perching on vertical twigs close to a big boulder five meters from the water’s edge. Although Dunkle (1993) speculated that perhaps H. azulum breeds on seepages, we did not see this habitat at any part of the stream. In the same stream we collected males and females of the common H. alienum , as well as other odonates such as Cora marina Selys, 1868 , Palaemnema desiderata Selys, 1886 , Erpetogomphus ophibolus Calvert, 1905 , and Brechmorhoga rapax Calvert, 1898 .

Figures

FIGURE 1. Heteragrion azulum habituses, left lateral view: a) Female; b) male.

FIGURE 2. Heteragrion azulum, female: a) Head, frontal view; b) same, dorsal view; c) partial view of thorax showing the intersternite; d) partial view of pterothorax showing black antealar crest and sinuses, dorsal.

FIGURE 3. Heteragrion azulum: a–c, Female; d–e, male: a) S7–10 showing coloration, dorsal view; b) S8–10 showing coloration, gonapophyses, and cerci, lateral view; c) S9–10 showing gonapophyses and cerci, ventral view; d) S10 and caudal appendages, dorsal view; e) ídem, dorsolateral view.

FIGURE 4. Heteragrion spp., dorsal view of female head: a) H. azulum; b) H. albifrons; c) H. alienum; d) H. tricellulare.

FIGURE 5. Heteragrion spp., females: a–c) Partial view of thorax showing intersternite, setifer, and posterior plate, lateral view; d–f) partial view of pterothorax showing the antealar crest and sinuses with large yellow spots, dorsal; g–i) S8–10 showing dorsal coloration. H. albifrons (a, d, g); H. alienum (b, e, h); H. tricellulare (c, f, i).