Gonioctena jacobsoni (Ogloblin & Medvedev, 1956)

Cho, Hee-Wook, 2019, Redescription of mature larva and biological notes on the nominotypical subgenus Gonioctena Chevrolat (Coleoptera: Chrysomelidae: Chrysomelinae) from South Korea, Zootaxa 4544 (4), pp. 557-571 : 560-561

Gonioctena jacobsoni (Ogloblin & Medvedev, 1956)

( Figs 13–18 , 27–28 , 38–41 )

Gonioctena (Gonioctena) jacobsoni: Medvedev & Zaitsev 1978: 120 (key to larva, illustration of mesonotum); Medvedev 1982: 179 (key to larva); Zaitsev & Medvedev 2009: 147 (key to larva, after Medvedev & Zaitsev 1978).

Last instar larva. Body length 8.5–8.9 mm, width 2.7–2.9 mm, head width 1.50–1.60 mm (n = 5). Body elongate, rather broad, widest at abdominal segments III–IV, thence moderately narrowed posteriorly and slightly convex dorsally ( Fig. 13 ). Color polymorphism present; dark type with dorsal tubercles brown to dark brown and ventral ones pale brown ( Fig. 40 ), sometimes pronotum unpigmented; light type with tubercles pale yellowish-brown except dorsal tubercles of abdominal segments VII–IX ( Fig. 39 ). General coloration of integument yellowish-white in alcohol, moderately covered with weakly sclerotized platelets; head blackish-brown with anterior half of clypeus yellowish-brown; legs yellowish-brown with apex of femur, tibia and tarsungulus dark brown. Eversible glands present on anterior margin of abdominal segment VIII. Pseudopods absent.

Head. Hypognathous, rounded, strongly sclerotized ( Fig. 14 ). Vertex with 5 pairs of minute setae; epicranium with 7 pairs of setae; temporal side of head with 4 pairs of setae. Epicranial suture distinct; frontal suture not reaching antennal socket; endocarina well developed. Frons slightly depressed medially, with 5 pairs of setae. Clypeus almost straight at anterior margin, with 3 pairs of setae. Labrum deeply emarginate with 2 pairs of setae and 1 pair of campaniform sensilla placed medially and 3 pairs of minute setae placed at anterior border ( Fig. 16 ); epipharynx with 3 pairs of stout setae at anterior margin. Mandible palmate, 5-toothed, with 2 setae and 2 campaniform sensilla ( Fig. 18 ). Maxillary palp 3-segmented; palpomere I transverse with 1 seta and 2 campaniform sensilla; II rectangular with 3 setae and 1 campaniform sensillum; III subconical with 1 seta, 1 digitiform sensillum and 1 campaniform sensillum on sides and a group of peg-like sensilla at the apex; palpifer distinct with 2 setae ( Fig. 17 ). Mala rounded with 15 setae and 1 campaniform sensillum; stipes longer than wide with 3 setae; cardo with 1 seta. Labial palp 2-segmented; palpomere I rectangular with 1 campaniform sensillum; II subconical with 1 campaniform sensillum on outer margin and a group of peg-like sensilla at the apex. Hypopharyngeal area with 3 pairs of minute setae and 2 pairs of campaniform sensilla. Prementum with 1 pair of setae; postmentum without spinules, with 3 pairs of setae. Stemmata 6 on each side, 4 of them located above antenna and 2 behind antenna. Antenna short, 3-segmented; antenomere I transverse with 2 campaniform sensilla; II stout, more or less as wide as long, with a conical sensorium and 4 minute setae apically; III subconical with 5 minute setae apically.

Thorax. Prothorax with D-DL-EP (13–17L 41–51S) largest; P (4S); ES-SS (2L 3S) (dark type in Fig. 27 , light type in Fig. 28 ). Meso- and metathorax with Dai (1L 3–4S); Dae (1L 2S); ad1 (1M) and ad2 (1M); DLai (5–8S); Dpi (1L 4–5S); Dpe-DLpi (1–2L 7–8S) larger than Dpi; DLe (4–5L 17–22S 1M) large and produced laterally; EPa (8–10S); EPp (2L 8–10S); P (1S 2M); SS (1S); ES (2L); sternal region with 4 additional setae arising from sclerotized bases. Mesothoracic spiracles annuliform; peritreme fused with EPa. Legs rather stout; tibia with 9 setae; tarsungulus large, strongly curved, basal tooth well developed, with 1 seta ( Fig. 15 ).

Abdomen. Segments I–VI with Dai, Dae and DLai enlarged and completely fused (3L 11–16S), forming a transverse band; DLae (1S 2M) small; Dpi and Dpe enlarged and completely fused (2L 6–8S), forming a transverse band; DLp (1L 3–6S 1M); EP (3–5L 13–16S) produced laterally; P (1L 6–10S 1M); PS-SS (4S) divided into 4 small tubercles; ES (1S); as1 (1S) and as2 (1S); sternal region with a short additional seta arising from sclerotized base. Segments VII–VIII each with dorsal and dorso-lateral tubercles completely fused (3L 18–21S 3–4M and 3L 10–12S 8–9M respectively). Segment IX with dorsal to epipleural tubercles completely fused (8–9L 7–11S 1–2M). Segment X with pygopod well developed. Spiracles present on segments I–VIII.

Diagnosis. The last instar larva of Gonioctena jacobsoni is similar to that of G. ogloblini in the fused dorsal tubercles on abdomen and presence of color polymorphism. However, this species can be distinguished from G. ogloblini by the dorsal and dorso-lateral tubercles on meso- and metathorax separated, DLae and DLp on abdominal segments I–VI separated from other dorsal tubercles, and light type with tubercles unpigmented except dorsal tubercles of abdominal segments VII–IX (tubercles fused and light type with all tubercles unpigmented in G. ogloblini ).

Material examined. 29 larvae, South Korea, Gangwon Prov., Pyeongchang-gun, Jinbu-myeon , Mt. Odaesan , 37°47'34.0"N, 128°33'39.7"E, 15.V.2005 , H.W. Cho; 30 larvae, same data as preceding one except for 5.V.2006 ; 5 larvae, same data as preceding one except for 26.V.2018 .

Distribution. Russia (East Siberia, Far East), Mongolia, China (Heilongjiang), South Korea.

Biological notes. Overwintered adults appear during early May ( Fig. 41 ). The first instar larvae are also found on the leaves of Populus maximowiczii during early May ( Fig. 38 ), but the eggs were not found in the field. This species is probably ovoviviparous. The larvae feed on the leaves, making small holes. The larva raises the tip of the abdomen everting glands when disturbed. The larvae are solitary during the instar stages, and the fourth instar larva pupates in soil. The adults emerge during early June; they feed and hibernate without mating. The larvae take 15–17 days to pupate, and then take 9–11 days to emerge as adults at room temperature.

Figures

FIGURES 13–18. Gonioctena jacobsoni, last instar larva. 13. lateral habitus; 14. head; 15. tibia and tarsungulus; 16. labrum; 17. maxillae and labium; 18. mandible.

FIGURES 25–29. Schematic presentation of tubercular patterns (top: prothorax; middle: mesothorax; bottom: 2 nd abdominal segment), last instar larva. 25. Gonioctena coreana; 26. Gonioctena gracilicornis; 27. Gonioctena jacobsoni, dark type; 28. Gonioctena jacobsoni, light type; 29. Gonioctena viminalis.

FIGURES 38–41. Gonioctena jacobsoni. 38. first instar larvae; 39. mature larva, light type; 40. mature larva, dark type; 41. adult.