Belostoma elongatum Montandon, 1908

Reyes, Cristina Armúa De, Estévez, Na. L. & Schnack, Juan A., 2006, Description of the preimaginal instars and redescription of the adult stage of Belostoma elongatum Montandon (Hemiptera: Belostomatidae), Zootaxa 1175 (1175), pp. 37-42 : 38-41

Belostoma elongatum Montandon

Belostoma elongatum Montandon,1908: 299 ; De Carlo, 1938: 214–215; Lauck, 1962: 77–78; Schnack, 1976: 33; Lanzer­de­Souza, 1980: 55–56.

Belostoma bosci, De Carlo, 1930: 112 .

Redescription of the adult ( Figs. 1–6)

Size: length: ♂♂: 35.0–38.0 mm, ♀♀: 35.5–38.8 mm; width: ♂♂ 13.5–15.0 mm, ♀♀: 14.0– 15.8 mm. Shape: body elongate, narrow ( Fig. 1). Color: yellowish brown.

Structural Characteristics

Head: suturae anteclipeus­maxillary plate longer than suturae anteclipeus­lorum; anteoculus as long as interoculus; eyes globose, as wide as long ( Fig. 1) beak: segment I longer than segment II ( Fig. 2).

Thorax: prosternal keel prominent, projecting anterad ( Fig.2). Profemur moderately dilated.

Abdomen: pilosity covering more than half of laterotergites, slightly narrower between spiracles, well­developed on penultimate segment ( Fig. 3); male genitali a with the arms of phallobase bending ventrad, covering lateral margins of the wide ventral diverticulum ( Figs. 4, 5, 6).

7–16 instars: 7 head, dorsal view; 8 head, first instar ventral view; 9 head, first instar, lateral view; 11 head, second instar, ventral view; 13 head, third instar, lateral view. Dorsal view showing body shape and forewing pad development: 10 first instar, 12 second instar, 14 third instar, 15 fourth instar, 16 fifth instar

Observations: this species is easily distinguished from its congeners by its characteristic narrow and elongate body shape, strikingly narrowed from the thorax to the head.

Type data: the types were cited by Montandon as follows: ” Paraguay: Asunción (Mus. Nat. Hung.), R. Apa (Mus. Zool. Turín) et ma collection”. These specimens probably are deposited at the Hungarian National Museum .

Material Examined

The adult specimens examined were those reared in the laboratory (5 ♂♂, 6 ♀♀) (see Table 1), those collected as adults and kept in the laboratory (5 ♂♂, 7 ♀♀), and specimens deposited in the (MLP) and (UNNE) The museum specimens bear the following data:

Argentina: Chaco: Resistencia 1 ♂ ( MLP) ; Resistencia 2­XII­1939, Birabén­Bezzi coll. 1♂, 5 ♀♀ ( MLP) ; Tirol. 7­XII­1939 Birabén­Bezzi coll. 1♂ ( MLP) ; Resistencia 10­II­ 1953, 1♀ ( MLP) . Corrientes: Bella Vista , 1♂ ( MLP) ; Berón de Astrada II­1947 Birabén coll. 1♀ ( MLP) ; Lag. González 7 ♂♂, 6 ♀♀, 15­VIII­ 2004 ( UNNE) ; Lag. Soto 1♂, 1♀, 15­ I­2004 ( UNNE) ; Saladas 3 ♂♂, (a la luz) 19­VI­2004 ( UNNE) . Santa Fe: Reconquista 26­ XI­1939 Birabén­Bezzi coll. 1 ♂ ( MLP) . Santiago del Estero: Río Salado , Wagner coll. 1 ♀ ( MLP) .

Descriptions of instars ( Figs. 7–16)

All descriptions except that of the fifth instar were based on the examination of dead specimens and the exuviae of those which molted.

First instar. Size: length: 6.0– 7.2 mm; width: 3.0– 3.6 mm. Shape: body elongate, narrow.

Head: anteoculus longer than interoculus; suturae anteclypeus­maxillary plate longer than suturae anteclypeus­lorum; eyes globose ( Fig.7), without grooves concealing antennae ( Fig. 8). Beak: segment I shorter than II ( Fig. 9). Antennae short, one­segmented, exposed, oriented forwards ( Fig. 8).

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.( Fig. 10). Prosternal keel pointed, not prominent. 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.

Material examined: dead nymphs (N: 11); exuviae (N: 24).

Second instar: Size: 8.3–9.0 mm; width: 3.9–5.1 mm. Shape: body elongate, narrow.

Head: Antennae small, two­segmented, oriented backwards ( Fig. 11).

Thorax: anterior margin of prothorax with a wide concavity; posterior margin of mesothorax with three projections of same length, one median and two lateral ( Fig. 12); prosternal keel sharp­pointed; leg I: internal claw reduced.

Abdomen: as in first instar.

Material examined: dead larvae (N: 7); exuviae (N: 17).

Third instar: Size: length: 9.8–10.7 mm; width: 5.6–7.3 mm. Shape: body elongate, narrow.

Head: with grooves concealing antennae, these three­segmented and with lateral processes Beak: segment I longer than II ( Fig. 13).

Thorax: anterior margin of prothorax with a less pronounced concavity than in previous instars; mesothorax: forewing pads larger than in previous instar, two deep concavities delimiting a V­shaped medial area, this longer than forewing pads; metathorax: with lateral rounded expansions ( Fig. 14).

Abdomen: first tergite reaching lateral margins.

Material examined: dead larvae (N: 2); exuviae (N: 15).

Fourth instar. Size: 11.0 – 12.7 mm; width 6.8–9.5 mm. Shape: body elongate, narrow.

Head: lateral processes of antennae longer than in third instar; grooves housing the antennae deeper than in third instar.

Thorax: mesothorax with wing pads larger than in previous instar, V­shaped medial area slightly shorter than forewing pads ( Fig.15).

Material examined: dead larvae (N: 4); exuviae (N: 11).

Fifth instar. Size: 12.7–14.3 mm; width 9.8–12.0 mm. Shape: body elongate, narrow. Head: antennae with lateral processes longer than in previous instar, fingerlike.

Thorax: mesothorax with wing pads reaching second abdominal segment; V­shaped medial area much shorter than wing pads ( Fig. 16).

Material examined: exuviae (N: 11).

Emergence (E) is herein referred as the molt to the instar or stage of development headed at each column (e.g., 25 first instars emerged (hatched) from egg s on February 13; 18 first instars molted to second instars on February 21; etc.)