Homoeusa gigantea Nozaki & Maruyama, 2025

Homoeusa gigantea Nozaki & Maruyama sp. nov.

Figs 3 F View Figure 3 , 15 A – I View Figure 15 , 16 A – E (Japanese name: Ô-hirata-ariyadori View Figure 16 )

“ Oxypodini View in CoL ? sp. 1 ”: Nishida 2019: 135, fig. 10 (recorded from Saga pref.).

Material examined.

Holotype (Fig. 3 F View Figure 3 ) • 1 ♂; “ [ Japan]: Fukuoka-ken, Soeda- ” / “ machi, Mt. Hikosan, Takasubaru ” / “ [ 33.4883, 130.9174], alt. 770 ” / “ m, 24. VII. 2022, Tsubasa ” / “ NOZAKI leg. LCH 01. ” / “ 添田町英彦山鷹巣原 ” // “ Lasius ” / “ umbratus ( Nylander, 1846) ” / “ アメイロケアリ ” / det. Tsubasa NOZAKI 2025 ” ( KUM). GoogleMaps

Paratype. Japan: Hokkaido • 1 ♀; Makoi, Shari-chô ; 28. V. 2000; Y. Kida leg. LUM ( KUM) • 2 ♀♀; Tôro lakeside, Shibecha-chô ; 28. VII. 1986; S. Nomura leg. ( KUM) • 2 ♀♀; Nopporo, Ebetsu-shi ; 13–21. VI. 2000; Shigehisa Hori leg. ( KUM) • 1 ex.; Minaminosawa, Sapporo-shi ; 16–23. V. 2023; Y. Tasaku leg. FIT ( HUM) • 1 ex.; Hakken-zan, Sapporo-shi ; 31. V. 2002; M. Maruyama leg. ( KUM) • 1 ♂; same locality; 20. VII. 2022; TS. Nozaki leg. LUU ( KUM) • 1 ex.; Obihiro-no-mori (alt. 78 m) [ 42.8987, 143.1439], Obihiro-shi ; 15. VII. 2022; TS. Nozaki & H. Nozaki leg. LUU ( KUM) GoogleMaps • 1 ex.; Higashi-ônura, Nanae-chô ; 16. VI. 1986; S. Nomura leg. ( KUM) . Honshu: Iwate-ken • 1 ♂, 1 ex.; Kitayama-sansakuro, Morioka-shi ; 2. V. 2020; N. Nakaya leg. LUU ( IPMM) • 1 ex.; Kitayama, Morioka-shi ; 23. IV – 3. V. 2024; N. Nakaya leg. FIT ( IPMM) • 1 ex.; Mt. Takabora, Kamiyonai, Morioka-shi ; 3. V. 2024; N. Nakaya leg. FIT ( IPMM) . Gunma-ken • 1 ex.; Yubisogawa, Minakami-machi ; 18. VI. 2004; M. Yasaka leg. ( KUM) . Nagano-ken • 2 exs.; Odairahara, Horigane (alt. 1,100 m), Azumino-shi ; 12. VII. 1998; M. Maruyama leg. LUU ( KUM) • 1 ex.; Fujii, Satoyamabe [ 36.2513, 137.3436], Matsumoto-shi ; 13. V. 2021; S. T. Inoue leg. LUU ( KUM) GoogleMaps • 1 ex.; Iriyamabe, Matsumoto-shi ; 30. VI. 2012; M. Maruyama leg. LUU ( KUM) • 1 ex.; Fujimi (alt. 1,510 m) [ 35.904, 138.190], Fujimi-chô ; 4. VI. 2023; TS. Nozaki leg. LUM ( KUM) GoogleMaps . Gifu-ken • 1 ♀; Nabedaira-kôgen, Takayama-shi ; 6. VII. 2022; TS. Nozaki leg. LUM ( KUM) • 2 ♂♂, 1 ♀; Nakao (alt. 1,200 m), Takayama-shi ; 5. VI. 2005; K. Kinomura leg. LUM ( KUM) • 1 ex.; Iwai (alt. 830 m) [ 36.1320, 137.3436], Takayama-shi ; 7. VII. 2022; TS. Nozaki leg. LUM ( KUM) GoogleMaps • 1 ex.; Iwase (alt. 850 m), Takayama-shi ; 5. V. 2005; K. Kinomura leg. LUU ( KUM) • 1 ex.; same locality; 4. VI. 2006; K. Kinomura leg. LUU ( KUM) . Nara-ken • 1 ♂; Wasamata-yama (alt. 1,140 m) [ 34.2184, 135.9862], Kamikitayama-mura ; 14. VI. 2023; TS. Nozaki leg. LUM ( KUM) GoogleMaps . Okayama-ken • 1 ex.; Jabuchi-no-taki, Mt. Nagi-san (alt. 579 m) [ 35.1567, 134.1908]; Nagi-chô ; 15. V. 2022; Y. Senda leg. ( EUMJ) GoogleMaps . Hiroshima-ken • 1 ex.; Kakezu-yama, Higashiyawatahara (alt. 850–1,126 m), Kitahiroshima-chô ; 27. VI – 4. VII. 2009; TA (Tatsuya). Nozaki & Yoko Nozaki leg. FIT ( KUM) . Shikoku: Kochi-ken • 1 ex.; Irazu-keikoku, Tsuno-chô ; 14. V. 2005; TA. Miyata & TO. Miyata leg. ( KUM) . Kyushu: Fukuoka-ken • 2 exs.; Takasubaru, Mt. Hikosan [ 33.4883, 130.9174], Soeda-machi ; 18. VI. 2021; TS. Nozaki leg. LUU ( KUM) GoogleMaps • 1 ♀, 1 ex.; same locality; 26. VI. 2021; TS. Nozaki leg. LUM ( KUM) GoogleMaps • 2 ♂♂; Biol. Lab. KU, Hikosan, (alt. 750 m) [ 33.4806, 130.9090], Soeda-machi ; 26. V. 2021; TS. Nozaki leg. LUU ( KUM) GoogleMaps • 1 ex.; Zuibai-ji, Itoshima-shi ; 8. V. 2021; T. Hashizume leg. ( KUM) • 3 exs.; Mt. Shaka-dake, Kitayabe, Yame-shi ; 18. V. 2017; S. Imasaka leg. FIT ( KUM) . Saga-ken • 1 ex.; Kurokami-yama, Arita-chô ; 27. IV. 2018; M. Nishida leg. FIT ( KUM) • 1 ex.; same locality; 9. V. 2018; M. Nishida leg. FIT ( KUM) . Kumamoto-ken • 1 ♂; Momiki (alt. 890 m) [ 32.494, 130.988], Yatsushiro-shi ; 24. V. 2023; TS. Nozaki leg. LUM ( KUM) GoogleMaps • 1 ♀; Mt. Shiratomi-yama [ 33.4883, 130.9174], Yatsushiro-shi ; 3. V. 2022; Y. Uehara leg. ( KUM) GoogleMaps . Oita-ken • 1 ♀, 3 exs.; Mt. Sobo ; 17. V. 1986; S. Nomura leg. ( KUM) • 1 ex.; Tsukahara, Yufu-shi ; 16. V. 2014; T. Hada leg. ( KUM) .

Diagnosis.

This species is distinguished from other species of the genus by the following combination of characteristics: pronotal posterolateral angle distinctly acute (Fig. 15 B View Figure 15 ); elytra distinctly widened posteriad entirely (Fig. 15 B, C View Figure 15 ); metaventral process slightly produced (Fig. 15 D View Figure 15 ); median lobe of aedeagus bulbous, length approximately 0.63 mm (Fig. 15 G View Figure 15 ). The appearance of this species is similar to H. laevigata and H. prolongata , but it can be distinguished from H. laevigata by its normal long setae of pronotum and elytra, and from H. prolongata by its larger body, aedeagus, and distinct acute posterolateral angle.

Description.

Body (Figs 3 F View Figure 3 , 16 E View Figure 16 ) large, broad, somewhat limuloid; dorsal surface mostly moderately polished.

Head small; color yellowish brown to brown; eyes small. Antennae (Fig. 15 A View Figure 15 ) short, relative length of each antennal segment from first to 11 th, 2.91: 2.25: 1.66: 1.27: 1.18: 1.2: 1.23: 1.18: 1.00: 1.45: 4.93.

Thorax. Pronotum (Fig. 15 B View Figure 15 ) semicircular, transverse ( PW / PL, 1.62–1.80), widest at posterior 1 / 3, postero-lateral angle distinctly acute, posterior margin distinctly sinuate, yellowish brown to brown, sometimes slightly transparent, surface finely covered with long setae and punctures, gently polished and slightly reticulated. Elytra (Fig. 15 B, C View Figure 15 ) distinctly widened posteriad entirely, posterior margins deeply notched near lateral corners, yellowish brown to brown, surface finely covered with long setae and punctures; gently polished and weakly reticulated. Hind wings developed. Mesoventral process (Fig. 15 D View Figure 15 ) very narrow, with indistinct medial carina, apex sharply pointed, reaching almost anterior margin of metaventrite. Metaventral process slightly produced (Fig. 15 D View Figure 15 ).

Abdomen elongate, remarkably narrowed posteriad; surface sparsely covered with short setae and each posterior margin with long stout setae; weakly reticulated.

Male: 8 th sternite (Fig. 15 E View Figure 15 ) weakly produced and angled at postero-medial margin; median lobe of aedeagus (Fig. 15 G View Figure 15 ) bulbous, length about 0.63 mm, apical lobe elogate and slightly curved ventrally, apex round in lateral view, apical valves elongate and mitten-shaped, dorsal arms short, basal part of copulatory piece large. Paramere (Fig. 15 H View Figure 15 ) length about 0.63 mm; apical lobe of paramere long, length about 1 / 3 of whole paramere, curved ventrally; four setae, b located more basally than c; velum small.

Female: 8 th sternite (Fig. 15 F View Figure 15 ) weakly produced roundly postero-medial margin; spermatheca (Fig. 15 I View Figure 15 ) S-shaped, apex of basal part slightly sinuate, base largely hooklike.

Variation.

Intraspecies variations were recognized in the apical lobe of the aedeagal median lobe. Some individuals have a small hump at the base of the ventral side and a slightly deeper basal concave. The length of the parameral apical lobe also varies slightly.

Measurements (in mm) and ratios.

Body parts (N = 10): BL ≈ 2.48–4.3; AL, 0.92–1.15; HW, 0.55–0.64; PL, 0.67–0.83; PW, 1.09–1.39; EL, 0.51–0.62; EW, 1.06–1.34; HTL, 0.61–0.75; PW / PL, 1.62–1.80; AL / PL, 1.22–1.46; HTL / PL, 0.89–1.02.

Distribution.

Japan ( Hokkaido, Honshu, Shikoku, Kyushu) (Fig. 16 A View Figure 16 ).

Symbiotic hosts.

Lasius umbratus species group: L. umbratus , L. meridionalis .

Bionomics.

Homoeusa gigantea sp. nov. is rarely observed in host ants’ trails under stones or soil from April to July (Fig. 16 B, C View Figure 16 ). Some individuals were collected by FIT (N = 15). Setting baits near the ants’ foraging trails under stones (like Fig. 1 C View Figure 1 ) is effective for collecting H. gigantea sp. nov. During indoor observations, they frequently and proactively rubbed their abdomen against body of their host ant workers (Fig. 16 B, D View Figure 16 ), unlike any other species of this genus.

Remarks.

Not many specimens were collected from foraging trails without bait. This might be because of the foraging behavior of the host ant species, Lasius umbratus and L. meridionalis . Both species are members of the Lasius umbratus group (formerly called the subgenus Chthonolasius Ruzsky, 1912 ) considered to forage mainly underground ( Donisthorpe 1927; Collingwood 1979; Seifert 1988). We also observed these Lasius species forming trails under stones or inside litter. Given this, we believe that they tend to forage mainly underground. To find Homoeusa gigantea sp. nov. in these trails naturally, first, a collector needs to find the trail. At the same time, the beetle must pass through the right stone on the long path all over the underground region. This is why a bait trap is effective. It can attract many ant workers and beetles under a particular stone. TN collected multiple individuals per bait set under a stone, suggesting that the species may potentially be more common than expected in their foraging trails.

Etymology.

The specific name is derived from the Latin adjective, which means “ huge ” and refers to the large size of this new species.