Thecagaster brevistigma (Selys, 1854)

Thecagaster brevistigma (Selys, 1854) View in CoL

General: The exuviae of T. brevistigma display the typical morphological features of Cordulegastridae larvae ( Fig. 9 View FIGURE 9 ). The body is uniformly brown with faint, darker colour patterns on the abdomen. The cuticle is covered with fine, sparsely distributed setae, found on the sternites, the abdominal tergites, and the dorsal side of the thorax. Additionally, longer setae and hairs are prominent along the posterior margin of the thorax, parts of the legs, the abdominal tergites, the leading edges of the sternites, and the appendages.

Head: In dorsal view, the lateral margins of the head behind the eyes are not parallel, giving the head a nonrectangular shape ( Fig. 10A View FIGURE 10 ). The occiput is irregularly hairy on the sides and posterior margin, with several strong lateral bristles pointing forwards and upwards ( Fig. 10A View FIGURE 10 ). The maximum head width is 7.7 mm. The clypeus is brown, the anterior margin is lined with a row of short setae. The compound eyes are conspicuously large and form the antero-lateral corners of the head. The segments of the antennae are incomplete ( Fig. 10A View FIGURE 10 ).

The labium shows a morphology typical for Cordulegastridae ( Figs. 10B–10C, 10E View FIGURE 10 ). In the resting position, the labium protrudes slightly beyond the middle coxae. Prementum ratio of length to width is 1.0. The cranial margin of the ligula is characterized by a densely packed row of very short setae, and medially by two cusps, each with a narrow distal protuberance ( Fig. 10D View FIGURE 10 ). Along the lateral edges of the prementum there is a row of more or less short, evenly spaced setae. The mesial margins of the palpal lobes are characterized by conspicuously irregular, pointed teeth, shown in Fig. 10B View FIGURE 10 , the tips of all teeth being strongly sclerotized, as indicated by their strong brown coloration. The movable hooks are long and robust, with a dark brown tip. In dorsal view, the prementum has four long and three short setae on each side ( Fig. 10E View FIGURE 10 ). The labial palpi bear four long bristles and the outer margins are lined with two rows of dense hairs ( Fig. 10E View FIGURE 10 ).

Thorax: The pronotum is broad and extends approximately to the vertical midline of the eyes. The wing sheaths extend to the fourth abdominal segment ( Fig. 9 View FIGURE 9 ). The tarsi consist of three segments with a two-part claw ( Fig. 11C View FIGURE 11 ). The segments are loosely covered with bristles, with strong spines at their proximal ends, especially on the ventral side.

Abdomen: All sternites are sparsely covered with bristles, whereby the density of bristles on the more caudal sternites decreases significantly. Each sternite and tergite has a dense row of short bristles along the posterior margin. Longer hairs are present on the sides of the abdominal segments, especially dense on the anterior segments ( Fig. 9 View FIGURE 9 ), the projection is about a third as long as the epiproct, distinctly notched in the middle, with parallel lateral margins and curved distal margins ( Fig. 11D View FIGURE 11 ). The cerci are short and reach only up to one third of the length of the paraprocts ( Fig. 11D View FIGURE 11 ). The paraprocts are just as long as the epiproct and form a pointed anal pyramid when closed. In lateral view, the epiproct and paraproct are strongly curved ventrally ( Fig. 11E View FIGURE 11 ). The abdomen lacks lateral and dorsal spines ( Figs. 11A–11B, 11E View FIGURE 11 ).

Measurements: (N=1, male): total length 36.8 (approximate value); head width 7.7 mm (approximate value); length of mentum 6.1 mm; basal width and distal width of mentum: 2.0 / 6.1 mm; length of wing case of hindwing: 10.0 mm; length femur foreleg (without trochanter) 4.3 mm; length tibia foreleg 5.2 mm; length tarsus foreleg 2.99 mm; length tarsal segments T1 0.6, T2 0.7, T3 1.7 mm; length abdomen: 24.5 mm; abdomen maximum width, 7.3; lengths cerci 1; cerci basal width 0.4; lengths paraproct (inner margin in ventral view) 2.9 mm males; lengths epiproct (in dorsal view): 3.2; lengths male projection: 0.7 mm; length of antennae not available.