Alcidodes erosa Mithun, Mahendiran & Pooja, 2025

Venugopal, Mithun, Pushkaran, Pooja, Pradeep, Nediyaparambu Sukumaran, Ranjith, Avinjikkattu P., Jose, Anna & Mahendiran, G., 2025, Alcidodes erosa (Coleoptera: Curculionidae), a new species from India feeding on Hopea erosa (Bedd.) Slooten, a critically endangered tree species of the Western Ghats, Zootaxa 5701 (4), pp. 483-491 : 486-488

Alcidodes erosa Mithun, Mahendiran & Pooja , sp. nov.

( Fig. 1 & 2 )

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Material examined: Holotype: male, INDIA, Kerala, Payyanikkotta, 11° 35 ’ 13.39 ” N, 75°52 ’ 8.12 ” E, 2.viii.2023, coll. Mithun, on seeds of Hopea erosa . Paratypes: 2 males, same data as the holotype ; 2 males, same data as the holotype except 27.ix.2024 (all types deposited at ICAR-National Bureau of Agricultural Insect Resources, Bengaluru, India) .

Length (excluding rostrum) 8.0– 11.4 mm (10.11 ± 0.3), Prothorax width at base 3.6–5.0 mm (4.62 ± 0.14), elytra width at humeri 4.6–6.6 mm (5.99 ±0.24) (n=5)

Head: Black, 0.70–0.83x as long as broad; coarsely punctate with yellow seta arising from each puncture. Eyes black, flat, oval-shaped, 1.58x as long as broad. Frons 0.33x as wide as head, punctate with yellow seta arising from each puncture, with deep circular central fovea. Rostrum brownish black, rostrum length, 3.6–5.2 mm (4.6 ± 0.16); length 5.07x width at base, straight, subcylindrical, widening towards apex, rostrum width at apex 1.02x rostrum width at base, sparsely and finely punctate, with yellow seta arising from each puncture; 1.22–1.48x as long as pronotum ( Fig. 2h ). Antenna brown, inserted behind middle of rostrum, ratio of distance from antenna insertion to base of rostrum and rostrum length 0.41 to 0.48; ratio of distance from apex to antennal socket and antennal socket to base of rostrum 0.68–0.95 (0.8 ± 0.06). Antennal scape almost reaching anterior margin of eyes, 5.4x as long as maximum width of scape; funicular segments sparsely setose with a row of stiff erect setae in each segment; funicular segment I and VII longer than other segments; funicle segment I 2.58–2.88x as long as segment II and 3.1–4.3x as long as segments III–VI; seventh funicular segment continuous with the club, moderately setose; segment VII 1.9–2.83x as long as segments II–VI; club 4 segmented, 1.19–1.4x as long as broad, densely setose in apical half of first club segment to the tip. The first segment of club is 0.45–0.51x as long as broad, 1.52–1.82x as long and 1.04–1.12x as long as segment 2.

Thorax: Sides of thorax in dorsal view sloping. Black, 0.69–0.78x (0.73 ± 0.04) as long as wide, with postocular lobes. Pronotum with slightly raised glossy sculptures on integument. Elytra with interstriae weakly wrinkled, strial punctures relatively deep, smaller than width of interstriae, striae appear as a row of large pits; elytral interstriae 2 and 3 not distinctly broader nor raised than 4; elytra broadest at the shoulder, 1.08–1.14x as long as broad, 1.30–1.62x as long as rostrum, 1.84–2.15x as long, 1.26–1.34 as broad as pronotum, apically convex; in lateral view, moderately convex; in dorsal view U shaped. Scutellum small, crescent shaped. Fore femur ( Fig. 2b ) with ventral tooth subtriangular, lacking proximal lobe, proximal margin slightly more than 90° to long axis of femur and shorter than length of tooth, distal margin dentate with 2 rows of 4 teeth each; fore femoral tooth length ranges from 0.529 –0.579, width of femur distal to tooth 0.621 –0.986, proximal margin length 0.293 –0.375, distal margin length 0.402 –0.657. All tibiae with (mid and hind femur with small) ventral tooth. Metasternum strongly produced posteroventrally before hind coxae, its ventral margin strongly diverging from elytral margin.

Abdomen: Ventrite V with two caudal setal tufts raised on weak prominences in male. Ventrite I 2.66–2.95 as long as ventrite II, 2.78–3.17 as long as ventrite III, 2.69–3.37 as long as ventrite IV, 1.9–2.09 as long as ventrite V; Ventrite III and IV subequal in length, ratio of length of ventrite III and IV 0.9–1.1. Hind coxae do not reach the margin of elytra.

Male genitalia: Tegmen with parameres fused at base ( Fig. 2f ). Aedeagus with apex rounded with an apparent blunt tip, bent downwards, sides rounded basally, weakly concave and converging towards apex, distance from ostium to apex much less than the width of ostium ( Fig. 2c, d, e ).

Female: Not known

Etymology: The specimens were collected from the seeds of the tree Hopea erosa of Dipterocarpaceae , and the specific epithet of the tree is used as the species name for this species.

Remarks: The new species, Alcidodes erosa belongs to the Alcidodes crassus group (as defined by Lyal & Curran, 2000) characterized by the underside of the fore femur with a large truncate preapical tooth lacking distal and proximal lobes, distal margin of tooth sloping and serrate, proximal margin of tooth straight, no teeth or projections on femur prior to proximal margin of single tooth, preapical tooth on mid femur of similar size and form to that on the fore femur and meta sternum strongly and obliquely produced posteroventrally on either side of midline. The new species is close to Alcidodes toyi Lyal but differs in the length of the proximal margin of the tooth on the fore femur, which is shorter than the length of the tooth in the new species while it is as long as length of tooth in A. toyi . The new species shows affinity to Alcidodes themus Lyal , but differs in the strial punctures narrower than interstriae, humeri with interstria 9 not projecting beyond 8 in dorsal view, fore femoral tooth with length of proximal margin generally less than half length of tooth, longer rostrum in the new species, whereas A. themus possess strial punctures that are deep and wider than interstriae, humeri with interstria 9 projecting beyond 8 in dorsal view, fore femoral tooth with length of proximal margin subequal or greater than distance of length of tooth, and shorter rostrum.

Adults lay eggs in young green fruits of Hopea erosa during the first and second weeks of June. The first and second instar larvae feed on the fresh green husky part of the fruit, and the third instar larvae bore through the husk/ shell and reach the kernel of the fruit. At this time, most of the infested fruits drop to the ground. Larval period lasts for 48 ± 5.4 days. Larvae start pupation inside the fallen fruits by early July, and the pupal period lasts for 13 ± 3.04 days. Adults start emerging while still inside the fruits in the last week of July and the middle of August. Fruit falls due to weevil infestation starts from the middle of June and extends up to August; most fruits fall during the third week of July. All the developmental stages of the insect life cycle (larvae, pupae and adults) have been found inside the fallen fruits. The larvae of the weevil are white, legless grubs that can consume most of the contents of a nut ( Fig. 2i ). These weevils pose the most a significant risk of injury to the host tree species. Integrated management would include the collection and disposal of the fallen fruits by burying them under 1.5–2.5 feet of compact soil and identification and conservation of the biocontrol agents found in the geographical region.

Damage to fruits:

This study evaluated the fruit damage in ten Hopea erosa trees (T1–T10) over three consecutive years (2022– 2024). The results are presented in the Table 2 . The data show that the mean fruit damage ranged from 77.71% (T7) to 81.71% (T3) across the ten tree species. The highest fruit damage was observed in T3 (81.71% ± 3.15%), followed by T8 (81.62% ± 3.56%) and T10 (81.50% ± 3.79%). In contrast, T7 showed the lowest mean fruit damage (77.71% ± 2.91%). Yearly variations in fruit damage were also observed. For instance, T2 and T8 showed significant increases in fruit damage from 2022 to 2023, while T5 and T7 exhibited decreases during the same period.

Figures

FIGURE 1. Adult habitus: a. dorsal view; b. lateral view.

FIGURE 2. Diagnostic characters and damaged fruit: a. forecoxa; b. fore femur tooth; c. aedeagus dorsal view; d. aedeagus lateral view; e. aedeagus tip; f. tegmen; g. spiculum gastrale; rostrum dorsal view; i. infested fruit with larva.