Apis ( Apis ) aibai, Takahashi & Takahashi, 2025

Apis ( Apis) aibai sp. nov.

Figs 2 View Figure 2 , 3 [New Japanese name: Tajima-mitsubachi View Figure 3 ]

Type material.

Holotype. • SOU-002 (Fig. 2 A, B View Figure 2 ). Worker / Female. An impressed / compressed individual in dorsal view. Head almost lacking. Mesosoma fine structures hard to interpret, with partly preserved obliquely outstretched forewings, hindwings, and hind legs. Metasoma outline and individual segments discernible. No counterpart. The holotype is deposited in the Museum of Unique Insect Fossils, Shin’onsen Town, Hyogo Prefecture.

Diagnosis.

Medium-sized honey bee (body length approximately 10.0 mm). Wings hyaline. Forewing length approximately 8.4 mm. Vein 1 Rs strongly slanted posterobasally, as long as vein 1 Rs + M, subparallel to vein 2 Rs, forming a slender subparallelogram-shaped 1 st submarginal cell. Cross vein 1 cu-a 0.7–0.8 times its length distant to vein 1 M (basal vein). Cubital index 4.5. Hind tibia 2.3 times longer than wide, as long as basitarsus. Abdomen 1.4 times wider than thorax.

Description.

Worker. Total body length 9.81 mm (as preserved). Head almost lacking, black in color.

Mesosoma apparently darker colored than metasoma, 3.52 mm long, 3.94 mm wide, with rounded outline. Pronotum black colored, not well preserved. Scutum 2.04 mm long, 2.98 mm wide, both anterior and posterior margins rounded. Scutoscutellar groove deep. Scutellum black colored, 0.52 mm long, with rounded posterior margin. Propodeum 0.56 mm long, 3.47 mm wide, with rounded posterior margin.

Forewing hyaline with complete venation, 7.8–8.1 mm long (as preserved). Reconstructed length approximately 8.4 mm long, width 2.9 mm wide. Marginal cell elongated, 3.12 mm long, 0.36 mm wide, about 8.6 times as long as wide, scarcely tapering apically, bluntly rounded at apex. Pterostigma small, 0.32 mm long, not projecting beyond cross vein r-rs. Vein 1 Rs straight, 0.54–0.57 mm long, strongly slanted posterobasally almost in line with vein 1 M, subparallel to vein 2 Rs. Vein 2 Rs weakly sinuate, 0.59–0.64 mm long, as long as vein Rs + M. Three submarginal cells present. 1 st submarginal cell slender subparallelogram in shape, vein Rs + M 0.56–0.60 mm long. Cross vein r-rs 0.30–0.36 mm long, as long as anterior margin of 2 nd submarginal cell. 2 nd submarginal cell elongated, due to posterobasally slanted 2 Rs and posteroapically slanted cross vein 1 rs-m. Vein 2 M straight, 0.54–0.56 mm long. Vein 3 M anteriorly arched, 1.23–1.25 mm. Anterior margin of cell short, 0.26–0.30 mm long, one-third of cross vein 1 rs-m. 3 rd submarginal cell relatively not large, subparallelogram in shape, anterior border not long, 0.61–0.67 mm long, posterior margin 0.59 mm long. Cross vein 1 rs-m sinuate, 0.90–0.91 mm long, almost parallel to cross vein 2 rs-m, meeting 2 nd medial cell in five-seventh of its upper base. Vein 4 M posteriorly arched, 0.49 mm. Cross vein 2 rs-m sinuate, 0.93 mm long, a without abscissal stub “ aRs 2 ”. 1 st medial cell subtrapezoid in shape, about 3.7–4.0 times as long as wide. Vein 1 Cu 1.45–1.55 mm long. Cross vein 1 m-cu 0.50–0.54 mm long, strongly arched outwardly at middle, joining 2 nd submarginal cell in one-fourth of its base. 2 nd medial cell large, subparallelogram in shape, about 2.2 times as long as wide. Vein 2 Cu 0.40 mm. Vein 3 Cu straight, 1.57 mm long. Cross vein 2 m-cu 0.85 mm long, weakly arched outwardly, meeting 3 rd submarginal cell in about five-sixth of its base (vein 5 M 0.11 mm long, cubital index about 4.5). Vein 1 M (basal vein) 0.93–1.01 mm long, slightly sinuate. Cross vein 1 cu-a 0.34–0.37 mm long, 0.27–0.28 mm distant to vein 1 M, perpendicular to vein A. Vein 2 Cu slightly slanted posterobasally, almost in line with cross vein 2 cu-a. 2 nd cubital cell elongated, apically widest, 1.67–1.80 mm long, 0.77–0.81 mm wide. Cross vein 2 cu-a 0.39–0.42 mm long, parallel to 1 cu-a.

Hindwing hyaline, reconstructed length 5.8 mm long. Humeri not preserved. Vein Sc + R straight. Rs almost straight, forming an angle of approximately 30 ° with vein R. Distal abscissa of vein Rs present. Distal abscissa of vein M uncertain. Cross vein cu-a 0.20–0.23 mm long, slightly inclined posteroapically. Vein A parallel to vein 1 M + Cu, forming elongated cubital cell. Jugal and vannal lobes uncertain.

Hind tibia not dark colored, widening apically, 2.01 mm long, 0.86 mm wide at most, dorsal margin slightly concave, ventral margin straight, without tibial spurs. Basitarsus enlarged and flattened, rectangular in shape, 1.92 mm long, 1.02 mm wide at middle, dorsal margin almost straight, ventral margin convex. 1 st mediotarsus largely widening apically, 0.40 mm long, 0.36 mm wide. 2 nd mediotarsus 0.25 mm long, 0.18 mm wide. 3 rd mediotarsus 0.25 mm long, 0.15 mm wide. Remaining portion poorly preserved.

Metasoma not dark colored, 5.15 mm long, 5.45 mm wide, with five terga (T 1 – T 5) visible. Darker colored bands remained on posterior parts of T 4 and T 5. T 1 widely transverse, 0.87 mm long, 4.49 mm wide. T 2 widest, 1.17 mm long, 5.45 mm wide. T 3 0.97 mm long. T 4 0.66 mm long, 4.77 mm wide. T 5 1.03 mm long, 4.09 mm wide. Sting? present at T 5, may be displaced forward during fossilization.

Etymology.

The species is named to honor Hiroaki Aiba, a Japanese paleontologist who described a new fossil species of a nymphalid butterfly found at the same fossil site in Umigami ( Aiba et al. 2025). He not only studied Japanese fossil insects but also contributed to Earth science education through the development of fossil collection activities.

Comparisons.

The forewing venation of the honey bees Apis is distinctive and can be easily recognized from the pattern and shape of the veins. For instance, the long marginal cell without apical tapering, the presence of three submarginal cells, and cross veins 1 rs-m and 2 rs-m strongly slanted posteroapically (e. g., Zeuner and Manning 1976; Engel 1999). In addition to these characteristics, the enlarged and flattened basitarsus proved that the studied material is a worker bee (Fig. 3 C View Figure 3 ). The reconstructed forewing length of the fossil clearly distinguished the dwarf and giant honey bee subgenera Megapis and Micrapis . The fossil material also does not match with extinct subgenera as vein 1 M (basal vein) of † Synapis is only slightly distad from cross vein 1 cu-a, straight vein 1 M of † Priapis is confluent with cross vein 1 cu-a, and the 3 rd submarginal cell of † Cascapis is larger ( Engel 2001). These facts demonstrate that the studied fossil is a member of the subgenus Apis .

As mentioned, five modern species comprise the subgenus, and we compared the fossil with them. The fossil clearly differs from A. mellifera and A. koschevnikovi because the cubital index of A. mellifera is much smaller and that of A. koschevnikovi is much larger than that of the new fossil (e. g., Hadisoesilo et al. 2008; Hassona 2017). The cubital index of A. nuluensis is also lower than that of the fossil specimen ( Tingek et al. 1996). The studied fossil resembles A. cerana , but the 1 st submarginal cell of the latter is not as slender as the fossil material ( Tan et al. 2008). Additionally, subspecies Apis cerana indica Fabricius has a longer hind tibia than that of the studied specimen ( Mattu and Verma 1984). Furthermore, in Japan, there is only one native honey bee subspecies, A. cerana japonica Radoszkowski , most of which have a forewing abscissal stub “ aRs 2 ” ( Tan et al. 2008). The forewing venation of the new fossil closely resembles that of A. nigrocincta , as vein 1 Rs is strongly slanted posterobasally, almost in line with vein 1 M, which forms the slender 1 st submarginal cell (Fig. 3 A – C View Figure 3 ). However, cross vein 1 cu-a is more strongly distad to vein 1 M in the latter, because the distance between vein 1 cu-a and vein M is shorter than the length of vein 1 cu-a itself, but that of A. nigrocincta is the same length or slightly longer.