Belostoma martini

Zaitha martini Montandon, 1899: 170 Belostoma martini Kirkaldy y Bueno, 1909:191; De Carlo, 1930:111, 1938: 230– 231, 1963: 99; Lauck, 1963: 99; Schnack, 1976: 37–38; Lanzer­de­Souza, 1980: 59.

Redescription of the adult (Figs. 2–9)

Size. Length: ɗɗ: 34.9–36.1 mm, ΨΨ: 35.0– 36.9 mm; width: ɗɗ 14.8–16.2 mm, ΨΨ: 15.1–17.3 mm. Shape: body ovate, slightly elongate (Fig. 2). Color: yellowish brown.

Structural characteristics

Head: suturae anteclypeus­maxillary plate longer than suturae anteclypeus­lorum; anteoculus longer than interoculus; eyes globose, as wide as long (Fig. 3) beak: segment I longer than segment II (Fig. 4). Thorax: prosternal keel prominent, acute, projecting downward (Fig.4). Profemur slender. Mesepimeron (dorsal view): ventromesal expansion reduced, not covering part of abdominal tergite II. Wing knob ovoid, clearly protruding from thewide posterior ridge. Postalar projection extending roughly from postalar bridge, forming a right angle; distal portion folded, developed longitudinally, gutterlike, extending more than half of total length of mesepimeron projection. Anterolateral widening of wing groove rounded, covered by long hairs. Metanotum densely pubescent (Fig. 5). Abdomen: pilosity entirely covering laterotergites, slightly narrower between spiracles, bordering genital operculum (Fig. 6); male genitalia bending ventrad, arms of phallobase converging in the middle, covering lateral margins of the wide ventral diverticulum (Figs. 7, 8, 9).

* Two fifth instars specimens reached the adult stage and their exuviae were described; thus this instar´s description was based upon the examination of six dead specimens and two exuviae. From the five females referred to the first capture, two of them emerged from the referred exuviae on January 6, 2006.

Length Width

Species of the Instars Stage Instars Stage Sources: instars 1 Schnack (1971); 2 Valverde & Schang (1994); 3 De Carlo (1939); 4Armúa de Reyes et al., (2006); 5 Schnack & Estévez (1978); 6Estévez & Schnack (this work); 7 Volpe (1985); adults 8 Schnack (1976).

Observations: The adults of this species are easily distinguished from the other members of the Belostoma dilatatum group (Lauck, 1963), to which it belongs, by its wide band of abdominal pilosity which extends bordering the genital operculum.

Type data: Montandon did not designate any types; he based the description of this species on specimens from Patagonia deposited at the Muséum National d’Histoire Naturelle (Paris).

Descriptions of instars (Figs. 10–16)

First instar. Size: length: 5.5–6.6 mm; width: 2.9–3.1 mm. Shape: body fusiform (Fig.10).

Head: anteoculus longer than interoculus; suturae anteclypeus­maxillary plate longer than suturae anteclypeus­lorum; eyes globose, without grooves concealing antennae. Antennae short, one­segmented, exposed, oriented forwards. Beak: segment I shorter than segment II (Fig.11). Thorax: anterior margin of prothorax concave, posterior margin straight; mesothorax with posterior margin bearing a wide median concavity; wing pads hardly visible on posterior lateral margins of mesothorax. Prosternal keel pointed, not prominent (Fig.11). Leg I: tarsus one­segmented with two claws, the inner one smaller. Abdomen: dorsum of first segment not reaching lateral margins; respiratory pads reaching posterior margin of second abdominal segment.

Second instar. Size: length 7.9–9.0 mm; width: 4.0– 4.5 mm. Shape: body fusiform (Fig. 12).

Head: Antennae small, two­segmented, oriented backwards. Beak: segment I shorter than segment II. Thorax: anterior margin of prothorax with wide concavity; posterior margin of mesothorax with three projections of same length, median one wider than lateral projections; prosternal keel sharp­pointed, not prominent; leg I: internal claw reduced. Abdomen: as in first instar.

Third instar. Size: length: 11.9–12.6 mm; width: 6.4–7.0 mm. Shape: body fusiform (Fig. 13)

Head: with grooves concealing antennae, these three­segmented and with lateral processes. Beak: segment I slightly shorter than segment II (Fig.14). Thorax: anterior margin of prothorax with less pronounced concavity than in previous instars; mesothorax: forewing pads larger than in previous instar, two deep concavities delimiting a U­shaped convex medial area, this as long as forewing pads; metathorax: sinuose, with lateral rounded expansions. Abdomen: first tergite reaching lateral margins.

Fourth instar. Size: 17.9–19.2 mm; width 8.9–10.0 mm. Shape: body fusiform (Fig. 15).

Head: lateral processes of antennae longer than in third instar; grooves housing the antennae deeper than in third instar. Beak: segment I longer than segment II. Thorax: mesothorax with wing pads larger than in previous instar, U­shaped medial area slightly shorter than forewing pads. Prosternal keel well developed, acute. Abdomen: as in third instar.

Fifth instar. Size: 25.5–27.0 mm; width 13.8–15.1 mm. Shape: body ovate, dilated (Fig. 16).

Head: antennae with lateral processes longer than in previous instar, fingerlike. Beak: segment I longer than segment II. Thorax: mesothorax with wing pads reaching second abdominal segment; V­shaped medial area much shorter than wing pads. Forewing pads as long as hindwing pads. Abdomen: as in fourth instar