Rhinusa neta (Germar, 1821)

Ścibior, Radoslaw & Letowski, Jacek, 2018, The morphology of the preimaginal stages of Rhinusaneta (Germar, 1821) and notes on its biology (Coleoptera, Curculionidae, Mecinini), ZooKeys 807, pp. 29-46 : 29

Rhinusa neta (Germar, 1821)

Description of egg.

Measurements (in mm). Egg length 0.47-0.51 (mean 0.49), width 0.25-0.29 (mean 0.27).

General. Oval, slightly oblate.

Colouration. Light yellow, smooth surface.

Description of mature larva.

(Figure 1, Table 1) Measurements (in mm). Body length: 4.40-4.50 mm (mean 4.46). The widest part of the body (Ab. I) 1.73-1.8 (mean 1.76). Epicranium: length 0.54-0.59 (mean 0.57), width 0.58-0.63 (mean 0.61).

General. Body massive, strongly curved.

Colouration. Head yellow-brown, body light yellow, covered with black, numerous setae.

Vestiture. Cuticle with strongly chitinised spots in several places on dorsal side. Asperities of body integument present on the surface of all thoracic segments and first abdominal segment covering area occupied by a group of setae prns and pds. Analogous structure presents only on the surface of the first pedal lobe.

Head capsule (Figure 2): Head slightly oval. Endocarina (enc) long, nearly 4/5 of frons length. One stemma (st) located at end of frontal suture at height of fs5. Frons with three distinct setae: longest (fs5) at base of antennae, fs1,4 located in the upper and lower part of frons near endocarina, and two small sensillae (unnumbered) close to fs4, which may be highly reduced setae fs2 and fs3. Dorsum of epicranium with five setae (des1-5); des3,5 longest and des1,2,4 of intermediate length. Posterior epicranium with four small setae (pes1-4) arranged in arc not far behind des2. On anterior epicranium two long setae les1-2 protrude from sides and visible vcs. Antennae (at) with conical sensorium and two very small spinose sensillae.

Clypeus with two setae of equal length (cls1, 2) at base with one sensilla between them.

Mouthparts (Figs 3-5): Dorsal side of labrum (Figure 3a) ca. 0.09 mm wide with three pairs setae (lms1-3). Longest lms1, setae lms2, 3 of similar length, only slightly shorter than lrms1. Anterior margin of epipharynx arched, with three thick setae laterally (als1-3), two setae (ams1-2) on anterior margin, and one seta (mes) medially, between well-formed, arcuate labral rods (lr) (Figure 3b). Mandibles (Figure 4) massive, red-brown, with two large teeth and one small tooth on inner side; medially on mandible three short setae (mds1-3) in one line. Maxillae (Figure 5) yellowish. Palpifer with one long, medially located seta sts1, two apically placed setae of equal length sts3-4 (or pfs 1-2) and one small sts2 (or mbs) below molar part. Maxillary palpus with two segments; basal segment with one very short seta (mxps) and two sensillae, distal segment cylindrical with accessory process on dorsal side and ten conical papillae. Mala with six setae of unequal length (dms1-6), arranged in one line, comb-like, and separate group of three setae (vms1-3) situated apically. Labium: postmentum with three setae of unequal length (pms1-3) - longest pms2 and shortest pms3. Prementum with two distinct teeth on basal part, three setae (prms1 and lgs1-2) and three sensillae. Seta prms1 very long, more than three times longer than lgs2. One pair lgs1 on apex and with them slightly larger pair lgs2 placed closer together. Labial palpus 1-segmented, with four shorter and one longer papilla located apically.

Thorax (Figure 6). Pronotal shields sclerotised, meso- and metanotum each with two folds: pro- and postdorsum. Spiracle unicameral, situated at intersegmental septum near pedal lobe. Prothorax with twelve setae: pronotum with seven (long prns1-6 and one short prs), epipleurum distinct with three setae of similar length (dpls1-2 and one vpls). Sternum outside pedal lobe with two setae (one lsts and one msts). Pedal area on prothorax much more sclerotised than other two, with six setae of similar length (ps1-6) on all segments of thorax. Chaetotaxy of meso- and metathorax analogous, consisting of eleven setae: mesonotum with five setae (pds1-3, one prs and one dls). Epipleurum with four setae (as1-3 and one vpls), sternum with two setae (one lsts and one msts). Pedal areas of meso- and metathorax unsclerotised.

Abdomen (Figure 6). Abdominal segments I-VII of similar shape. Tergites I-VII with two folds, prodorsum with one seta on ridge (prs1), postdorsum with five setae: four located dorsally (pds1-3, dls1) and one, longest seta (ss) on spiracular area. Epipleurum with four setae (dpls1-3 and 1 vpls), sternum with two setae (one lsts and one msts). Segments I-VIII with unicameral spiracles, others (IX-X) without spiracles. Segment VIII with two folds, setae arranged as on segments I-VII, except for lack of seta prs. Segment IX with four setae, two on pleura (one ds and one ls) and two on sterna (one ls and one sts). Segment X with two small setae, one on pleura and one on sterna (both ts).

Description of pupa.

(Figs 7-9, Table 2) Measurements (in mm). Body length: 3.32-3.40 (mean 3.35), width (between the apex of mesofemora) 1.90-1.98 (mean 1.92).

Colouration. Yellow-brown with distinct chaetotaxy.

Head (ventral view): rostrum reaches end of mesothorax, with one short seta (drs) apically. Head with distinct eyes and one seta (sos) at their inner edge. Antennae at base of rostrum. Massive. Thorax: pronotum wider than long, trapezoid-shaped, with two distinct, highly sclerotised, bare tubercles at anterior margin, with eight long setae: aps1-2, lps1-3, dps2, and bps1-2 (Figs 7-9). Mesonotum longer than metanotum. Latter with two clearly visible scutellar shields posteriorly. Dorsal part of meso- and metanotum with three setae (msns, mtns) of unequal length located laterally. All femora with one long, thin seta (fes) located apically. Abdomen: tergites I–VII with four setae in one row slightly beyond midpoint of segment. Longest located near lateral outer margin, on segments I-V below spiracle entrance, on others (VI-VII) centrally. Of three remaining setae, two short - centrally located and third from middle of segment, second from centre somewhat shorter, but clearly shorter than outer seta. Segment VIII with four setae, shortest located medially, longest approx. three times longer than first. Segment IX with one distinct urogomphi, darker, bent back, highly chitinised (pseudocerci - pc) (Figs 7, 8). Sternites: segments I-VIII with four setae arranged in one row, of similar length except longest pair located medially (Figs 7, 9). Spiracles on abdominal segments I-V placed laterally, functional. Pleurites (III-VIII) with seta of equal length, slightly shorter and curved on segment VIII, pleurites (I-II) without setae (Figure 7).

Biological information.

After overwintering, adults emerge in May and June, depending on weather conditions in the year ( Burakowski et al. 1997; Wilson et. al 2005). Initially, they feed on the vegetative parts of plants, and after the inflorescence has been formed they feed on the generative parts. After copulation, the females lays eggs into channels bored in the seed capsules and then uses excrement to seal the hole. One or two larvae were usually observed in one seed capsule. Approximately 10-12 days after eggs were laid eggs in the laboratory, L1 larvae appeared, which fed on the seeds without causing them to swell. The full larval stage lasted on average 29 days, followed by pupation. This stage lasted approximately 18 days. The full development cycle of the beetle in laboratory conditions averaged 58 days. Some larvae died in the seed capsules, having been attacked by parasitic hymenopterans of the superfamily Chalcidoidea, with parasitism reaching 20%. Species complete one generation per year and the new generation of adults emerge in August and September.