Gonioctena viminalis (Linnaeus, 1758)

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 : 561-567

Gonioctena viminalis (Linnaeus, 1758)

( Figs 19–24 , 29 , 42–45 )

Chrysomela (Gonioctena) viminalis: Letzner 1855: 109 (description of larva, pupa).

Phytodecta viminalis: Henriksen 1927: 335 (description of larva, key, illustration of larval habitus); Medvedev 1964: 508, 509 (illustration of larval habitus, head).

Phytodecta (Phytodecta) viminalis: Hennig 1938: 119 , 123 (description of larva, key, illustration of pronotum); Ogloblin & Medvedev 1971: 74 (key to larva, illustration of abdominal segment III).

Gonioctena (Gonioctena) viminalis: Medvedev & Zaitsev 1978: 119 (key to larva, illustration of frons, clypeus, labrum, mesonotum, tarsus); Booth et al. 1990: 281 (illustration of larval habitus, after Medvedev 1964); Steinhausen 1966: 319 (illustration of labrum), 1994: 277 (key to larva, illustration of abdominal segments I–II, VII–VIII, tarsugulus); Warchałowski 1994: 103 (key to larva); Zaitsev & Medvedev 2009: 146 (key to larva, after Medvedev & Zaitsev 1978).

Last instar larva. Body length 9.2–10.2 mm, width 2.9–3.1 mm, head width 1.70–1.80 mm (n = 5). Body elongate, rather broad, widest at abdominal segments III–IV, thence moderately narrowed posteriorly and slightly convex dorsally ( Fig. 19 ). General coloration of integument yellowish-white, but densely covered with strongly sclerotized platelets; tubercles dark brown, whereas ventral ones paler; head blackish-brown with anterior half of clypeus yellowish-brown; legs dark brown to brown. Eversible glands present on anterior margin of abdominal segment VIII. Pseudopods absent.

Head. Hypognathous, rounded, strongly sclerotized ( Fig. 20 ). Vertex with 4 pairs of minute setae; epicranium with 8 pairs of setae; temporal side of head with 2 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 2 pairs of minute setae placed at anterior border ( Fig. 22 ); epipharynx with 3 pairs of stout setae at anterior margin. Mandible palmate, 5-toothed, with 2 setae and 2 campaniform sensilla ( Fig. 24 ). 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. 23 ). 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 baso-laterally covered with 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 6 minute setae apically.

Thorax. Prothorax with D-DL-EP (15–21L 32–36S) largest; P (4S); ES-SS (5–6S) ( Fig. 29 ). Meso- and metathorax with Dai (1L 1S); Dae (1L 1–2S); ad1 (1M) and ad2 (1M); DLai (2–4S); Dpi (1L 2–3S); Dpe-DLpi (3L 4–6S) larger than Dpi; DLe (3–5L 10–11S) large and produced laterally; EPa (2L 5–7S); EPp (3L 4–5S); P (3S); SS (1S), ES (2–3S); sternal region with 5 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. 21 ).

Abdomen. Segments I–V with Dai (1L 2S) on both sides fused; Dae (1L 2–3S); DLai (1L 3–4S); DLae (1S 2M) divided into 2 small tubercles; Dpi (1L 2–4S); Dpe (1L 2–3S); DLp (1L 3–4S 1M); EP (3–4L 6–7S) produced laterally; P (4S 2–3M); PS-SS (4S); ES (2–3S); as1 (1M) and as2 (1S); sternal region with a short additional seta arising from sclerotized base. Segment VI with Dai and Dae partially fused, Dpi on both sides fused. Segment VII with dorsal and dorso-lateral tubercles fused completely (6L 9S 2M) except for DLae. Segment VIII with D-DL (6L 7–10S 6–10M). Segment IX with D-DL-EP (6–8L 8–11S 2M). Segment X with pygopod well developed. Spiracles present on segments I–VIII.

Diagnosis. The last instar larva of Gonioctena viminalis is very similar to that of G. gracilicornis in the body shape, coloration, and tubercular pattern. However, this species can be distinguished by the tubercles covered with relatively short setae (relatively long in G. gracilicornis ), tubercle Dpi on both sides of abdominal segments I–V weakly fused (completely fused in G. gracilicornis ), and basal tooth of tarsungulus well developed (weakly developed in G. gracilicornis ).

Material examined. 21 larvae, South Korea, Gangwon Prov., Taebaek, Hwangji-dong , Jeolgol Valley , 37°10'26.9"N, 128°57'13.5"E, 5. VI.2005 , H.W. Cho; 8 larvae, South Korea, Gangwon Prov., Pyeongchang-gun, Jinbu-myeon , Bangadari, 37°41'43.2"N, 128°30'12.7"E, 31.V.2006 , H.W. Cho; 4 larvae, South Korea, Gangwon Prov., Pyeongchang-gun, Jinbu-myeon , Mt. Odaesan , 37°47'06.0"N, 128°33'31.7"E, 31.V.2006 , H.W. Cho; 3 larvae, same data as preceding one except for 7. VI.2009 ; 3 larvae, same data as preceding one except for 26.V.2018 ; 5 larvae, South Korea, Gangwon, Pyeongchang-gun, Bongpyeong-myeon, Heungjeong Valley , 37°39'55.7"N 128°18'05.6"E, 21.V.2018 , H.W. Cho; 19 larvae, South Korea, Gangwon Prov., Pyeongchang-gun, Daegwallyeong-myeon , Hoenggye-ri, 37°40'49.2"N, 128°44'58.1"E, 27.V.2018 , H.W. Cho.

Distribution. Widespread trans-Palaearctic species from UK to Russian Far East.

Biological notes. Overwintered adults appear during early May ( Fig. 45 ). A female laid 11 larvae, which were not enclosed within chorion ( Fig. 42 ), as reported previously from Europe ( Cornelius 1857). Maternal care has been reported by studies in Europe ( Lengerken 1939; Vasconcellos-Neto & Jolivet 1994); however, it has not been observed in South Korea. The larvae gregariously feed on the leaves of Salix caprea , Salix koreensis , and Salix maximowiczii until the final instar ( Fig. 43 ). They raise the tip of the abdomen everting glands when disturbed ( Fig. 44 ). There are four larval instars, and pupation occurs in soil. Adults emerge during early June; they feed and hibernate without mating. The larvae take 13–15 days to pupate, and then take 8–10 days to emerge as adults at room temperature.

Figures

FIGURES 19–24. Gonioctena viminalis, last instar larva. 19. lateral habitus; 20. head; 21. tibia and tarsungulus; 22. labrum; 23. maxillae and labium; 24. 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 42–45. Gonioctena viminalis. 42. newly laid larvae; 43. early instar larvae; 44. mature larva everting glands (arrow); 45. adult.