Demarchus hsui, Lee & Chen, 2023

Lee, Chi-Feng & Chen, Jung-Chan, 2023, Demarchus hsui (Coleoptera, Chrysomelidae, Galerucinae, Alticini), a new species from Taiwan, with notes on immatures and biology, ZooKeys 1177, pp. 3-21 : 3

publication ID	https://dx.doi.org/10.3897/zookeys.1177.97854
publication LSID	lsid:zoobank.org:pub:E867FD68-1EF1-49FC-8DE7-ACC73F837CA8
persistent identifier	https://treatment.plazi.org/id/6F1961AF-38D3-4C8D-AE84-B2E5127098AB
taxon LSID	lsid:zoobank.org:act:6F1961AF-38D3-4C8D-AE84-B2E5127098AB
treatment provided by	ZooKeys by Pensoft
scientific name	Demarchus hsui
status	sp. nov.

Treatment

Demarchus hsui sp. nov.

Figs 1 View Figure 1 , 2 View Figure 2 , 3 View Figure 3 , 4 View Figure 4 , 5 View Figure 5 , 6 View Figure 6 , 7 View Figure 7

Type material.

Holotype ♂ (TARI, The Insect Collection, Applied Zoology Division, Taiwan Agricultural Research Institute, Taichung, Taiwan): Taiwan. Hualien: Pilu (碧綠), 20.VI.2022, leg. Y.-F. Hsu. Paratypes: 7♂, 10♀ (3♂, 3♀: BMNH; 4♂, 7♀: TARI), data same as holotype; 4♂, 4♀ (TARI) same locality as holotype, 13.VII.2022, leg. Z.-I. Chen.

Additional material examined.

Five mature larvae (TARI), same locality as holotype, 20.IX.2022, leg. Y.-F. Hsu.

Description.

Adults. Colour (Fig. 1A-C View Figure 1 ) reddish brown, head black, but antenna dark brown or black, prothorax pale yellow, legs yellow with outer margins blackish brown. Pronotum transverse, 2.0 × wider than long, disc convex and with lateral fovea, disc with sparse, coarse punctures, lacking antebasal transverse groove; lateral margin rounded, anterior margin slightly concave, posterior margin slightly convex. Elytra slightly wider posteriorly, with shallow transverse impression, widest at apical 1/3, apex convergently rounded, 1.5-1.7 × longer than wide, disc with dense, fine punctures and dense pubescence.

Male. Length 4.8-5.5 mm, width 2.2-2.5 mm. Antenna filiform (Fig. 2A View Figure 2 ), ratio of length of antennomeres I to XI 1.0: 0.5: 0.6: 0.8: 0.8: 0.9: 0.9: 0.8: 0.7: 0.7: 0.9; ratio of length to width of antennomeres I to XI 3.0: 2.4: 3.1: 3.0: 3.2: 3.3: 3.4: 3.6: 3.2: 3.2: 3.9. Aedeagus (Fig. 2C-E View Figure 2 ) with apical 1/2 lanceolate, apex narrowly rounded, basally narrowed; strongly curved in lateral view, slightly recurved near base; tectum slightly sclerotised, with median, longitudinal, strongly sclerotised area from basal margin; endophallic sclerites absent. Apex of abdominal ventrite V (Fig. 2I View Figure 2 ) with median, angular notch, internally covered by flattened sclerite.

Female. Length 5.1-6.0 mm, width 2.4-3.0 mm. Antenna (Fig. 2B View Figure 2 ) similar to males, ratio of length of antennomeres I to XI 1.0: 0.5: 0.6: 0.9: 0.9: 0.8: 0.8: 0.7: 0.7: 0.6: 0.9; ratio of length to width of antennomeres III to XI 3.6: 2.6: 2.7: 3.7: 3.6: 3.5: 3.7: 3.4: 3.5: 3.0: 4.5. Ventrite VIII (Fig. 2F View Figure 2 ) weakly sclerotised, T-shaped, with dense, short setae along apical margin, apical margin irregular, spiculum short. Spermathecal receptaculum (Fig. 2G View Figure 2 ) slightly swollen; pump long and strongly curved, apex widely rounded; spermathecal duct short, shallowly projecting into receptaculum. Gonocoxae (Fig. 2H View Figure 2 ) short and widely conjoined at base, each gonocoxa widest at apical 1/3, with dense setae along apical areas.

Diagnosis.

Adults of this new species are similar to those of D. nigriceps in colour pattern, but differ in possessing black antennae and outer margins of tibiae (Fig. 1A-C View Figure 1 ) (yellow antennae and tibiae in D. nigriceps (Fig. 11C, F View Figure 11 )), pronotum without antebasal transverse groove (Fig. 1A View Figure 1 ) (pronotum with antebasal transverse groove in D. nigriceps (Fig. 11C View Figure 11 )), elytra with transverse impression (Fig. 1A View Figure 1 ) (elytra without transverse impression in D. nigriceps (Fig. 11C View Figure 11 )), antennomeres IV-VII subequal in length and longer than antennomere III (IV-VII subequal in length and shorter than antennomere III in D. nigriceps ), antennomeres VIII-X subequal in length and shorter than antennomere XI (antennomere VIII-XI subequal in length in D. nigriceps ).

Mature larvae.

Length 9.5-9.6 mm, width 2.5-2.6 mm. Live specimens (Fig. 7E View Figure 7 ): body form elongate, flattened; pale yellow, head and legs blackish brown; prothoracic and abdominal tergite IX with large sclerotised patches; thoracic tergites with small, longitudinal, curved sclerotised patches at sides; thoracic ventrites with small rounded sclerotised patches medially; lateral margins of meso- and metathoracic, and abdominal segments I-VIII expanding outwards, abdominal segments I-VIII each bearing one small process at lateral margins. body bearing tiny setae, the latter sometimes reduced to pores. Spiracles present on mesothorax and abdominal segments I-VIII (Fig. 3A View Figure 3 ).

Head (Fig. 4A View Figure 4 ). Flattened, narrower than prothorax, partly retracted into prothorax; frontal sutures (Frs) V-shaped, epicranial suture (Eps) short; endocarina (En) wide. Stemmata absent. Epicranium (Ep): with six pairs of short setae (e1-7) and nine pairs of pores (p1-9); e4-6 situated at posterolateral part of epicranial halves. Frons (Fr): with three pairs of short setae (f1-3) and one pair of pores. Clypeus (Cly): transverse, with three pairs of tiny setae near base. Clypeus and frons devided by apistomal sulcus. Labrum (Lbr): transverse, with one pair of short setae near midline; apical edge rounded. Epipharynx (Fig. 4E View Figure 4 ): densely setose anteriorly; with four or five large setae on each side; sensilla arranged in one pair of transverse rows. Mandibles (Fig. 4D View Figure 4 ): symmetrical, palmate, each mandible with four sharp teeth, without penicillus. Antennae (Fig. 4C View Figure 4 ): weakly sclerotised, two segmented, attached to membranous area at end of frontal suture; first antennomere partly membranous, bearing one small conical sensory papilla and several sensilla; second antennomere small, without sensilla. Maxilla (Fig. 4B View Figure 4 ): Stipes (St) elongate, bearing one pair of long setae and two pairs of short setae near lateral margin; with a long, curved sclerotisation (Scl). Mala with galea (Gal) and lacinia (Lac) not fused; galea wide, bearing six stout setae and numerous hair-like setae at apex; apical part of lacinia with dense hair-like setae; maxillary palpus (Mxp) three-segmented, second palpomere bearing two setae, one and third palpomeres each bearing one sensilla. Labium (Fig. 4B View Figure 4 ): submentum (Smen) trapezoid, bearing two pairs of long setae at sides; mentum not well defined; prementum short and transparent, with horseshoe-shaped mental sclerite (Mens), bearing one pair of setae at base; ligula (Lig) membranous, not separated from prementum, anterior edge broadly concave, bearing numerous hair-like setae; labial palpi (Lbip) small, two segmented; with three pairs of sensilla near labial palpi.

Thorax. Prothorax: dorsum (Fig. 3B View Figure 3 ) with one pair of pores and two pairs of short setae at basal areas of sclerotised patches; two pairs of short setae near base halfway between sclerotised patches and bases of lateral process; three pairs of short setae at sides. Sternal region (Fig. 3D View Figure 3 ) with one small, sclerotised patch medially, two pairs of short setae at anterior and posterior parts of sclerotised patch respectively. Mesothorax: dorsal region (Fig. 3B View Figure 3 ) with pores and short setae arranged into two transverse rows, anterior row with two pairs of pores and one pair of setae, posterior row with four setae; lateral longitudinal, sclerotised patches bearing three short setae. Sternal region (Fig. 3D View Figure 3 ) with one very small, sclerotised patch, one pair of short setae and one pair of pores at anterior and posterior parts outside sclerotised patch. Metathorax: same pattern as mesothorax, except for absence of spiracle. Legs (Fig. 4F View Figure 4 ): five segments; trochantin (Tn) triangular, without setae or pores; coxa (Co) transverse, bearing several pores at basal half, and two short setae near apical margin; trochanter (Tr) triangular, lacking setae but with several pores; femur (Fe) small, with one long seta on mesal margin, and one small setae at inner face; tibia (Ti) enlarged at base decreasing toward apex, bearing seven short setae at apical 1/2; tarsungulus sclerotised, falciform, bearing one basal setae; pulvillus (Pu) bladder-like, as long as tarsungulus.

Abdomen. Segments I-VIII: dorsal region (Fig. 3C View Figure 3 ) lacking setae, pores arranged into two transverse rows, bearing three pairs of pores at anterior and posterior row respectively, and three pairs of pores on lateral process; sternal region (Fig. 3E View Figure 3 ) with pores arranged into three transverse rows, one pair of pores in anterior row, four pairs of pores in middle row, and two pairs of pores in posterior row, three pairs of pores on lateral process. Segment IX (Fig. 4G View Figure 4 ): pygidium moderately sclerotised; disc with pores arranged into two transverse rows, three pairs of pores in anterior and posterior rows respectively; three pairs of short setae along lateral margin.

Host plant.

Loranthaceae : Taxillus rhododendricolus (Hayata) S.T. Chiu.

Biology.

Larvae are leaf miners of Taxillus rhododendricolus , which is a hemiparasite. More than 20 larvae (Fig. 5C-E View Figure 5 ) were collected from branches (Fig. 5A, B View Figure 5 ) cut from the host tree, Salix fulvopubescens Hayata var. fulvopubescens Hayata (褐毛柳) at a height of approximately six meters during late August 2020. Forest type is mixed coniferous, including Picea asperata Mast., Tsuga chinensis (Franch.) Pritzel ex Diels., and Cunninghamia konishii Hayata, with some evergreen broad-leaved and deciduous trees. During 2022, 18 adults were collected using sweep nets from the same plant on June 20 by Dr. Hsu (see types). Eight additional adults were collected from the host plant on trees of Carpinus rankanensis Hayata on July 13. Some other collecting trips were carried out during different months. These collecting events indicated that adults appear during June and July, egg masses during early August, and larvae only during late August and September, no life stages were found after October, and it is clear that D. hsui sp. nov. is an univoltine species. By contrast, populations of D. pubipennis in Pakistan are multivoltine, with up to four generations a year ( Mushtaque and Baloch 1979).

Egg masses were deposited at some distance from each other on undersides of leaves (Fig. 6A View Figure 6 ). Females scratched the leaf surface several times (Fig. 6B View Figure 6 ) so that neonate larvae could burrow into the leaves easily. Then four or five eggs (Fig. 6C View Figure 6 ) were laid and covered by faeces. Usually only one larva hatched successfully from each egg mass (Fig. 6D View Figure 6 ) and began mining leaves.

Leaves of T. rhododendricolus decayed as soon as larvae constructed tunnels (Fig. 7A View Figure 7 ). Tunnels made by larvae were always transverse and turned towards the leaf apex (Fig. 7B, C View Figure 7 ). Larvae turned tunnels basally when conditions were not suitable to maintain the apical direction. Such a feeding pattern caused the entire leaf to decay from apex to base (Figs 5D, E View Figure 5 , 6D View Figure 6 , 7B View Figure 7 ). Larvae exited tunnels when conditions deteriorated and searched for more suitable leaves. They were able to tunnel into newly selected leaves and continue development (Fig. 7D View Figure 7 ). Mature larvae (Fig. 7E View Figure 7 ) emerged from tunnels and walked or fell to the ground, mainly falling when disturbed. They burrowed into soil and built underground chambers for pupation.

Adults on leaves of T. rhododendricolus were active during the day (Fig. 7F View Figure 7 ). They fed on the upper surface of leaves, leaving round feeding scars (Fig. 7B, E View Figure 7 ).

Remarks.

Larvae of D. hsui sp. nov. exhibit unusual characters that are typical for leaf miners ( Takizawa 2005), including flattened body and head, head with vertex incised in a U- or V-shape posteriorly, and body surface without setae or tubercles.

Etymology.

This new species is named for Dr. Yu-Feng Hsu (徐堉峰), who is a well-known butterfly expert and the first person to collect specimens.

Distribution.

The new species is only recorded from the type locality -- Pilu (碧綠), in Hualien County, East Taiwan. It is located at 24°10'51.3"N, 121°24'11.6"E, 2150 m MSL, and protected by the Taroko National Park (太魯閣國家公園). This locality seems to be the biodiversity hotspot. The rarely collected chrysomeline Ambrostoma chinkinyui Kimoto & Osawa, 1995 is also only known from this locality ( Kimoto and Osawa 1995), as well as multiple undescribed species (unpublished data).