Vespa Linnaeus, 1758

Lee, John X. Q., Soh, Zestin W. W., Chui, Shao Xiong, Leong, Andrea Q. E., Ong, Christabel N. Y. & Ascher, John S., 2023, Hornets (Vespidae: Vespinae) of Singapore: ecology, identification, and national conservation assessment, Raffles Bulletin of Zoology 71, pp. 457-477 : 461-466

Vespa Linnaeus, 1758 Vespa affinis ( Linnaeus, 1764)

Lesser Banded Hornet ( Figs. 3 , 4A , 6 )

Apis affinis Linnaeus, 1764: 417

Vespa indosinensis Pérez, 1910 , Actes de la Société linnéenne de Bordeaux 64:8, female –

“ Cochinchine, Annam” (M. Boutan); Malacca; Celebes septentrionalis; India (lectotype from Annam ( Vietnam)) - van der Vecht, 1957, Zoologische Verhandelingen 34:28 (designation of lectotype) .

Global distribution. Bangladesh; Bhutan; Cambodia; China (mainland, Hainan, Hong Kong, Macao); Indonesia (Greater Sundas, Wallacea, West Papua); India; Japan (Ryukyu Islands); Laos; Malaysia (Peninsular, Sabah, Sarawak); Myanmar; Nepal; New Britain; New Ireland; Papua New Guinea (including New Britain); Philippines (including Palawan); Singapore; Sri Lanka; Taiwan; Thailand; Timor- Leste; Vietnam. It has also been reported elsewhere (e.g., California, USA; New Zealand) as an introduced species ( Smith-Pardo et al., 2020).

Diagnosis. A medium-sized hornet, workers averaging 20–26 mm, males averaging 24–26 mm and queens reaching 30 mm in total body length. The colour form found in Singapore has a black ground colour, including the head (red in some extralimital populations), with most of the first and all of the second gastral terga orange ( Fig. 3 ). Darker specimens, which are uncommon, have the first tergum largely or fully black ( Fig. 3A ), thus differing only subtly in colouration from V. tropica , most notably in the wings which are more uniformly dark in colour with less lightening at the tips than in V. tropica . These unusually-coloured individuals are therefore best identified by structural characters noted in the key, such as the broad paired lobes on the clypeal apex (as opposed to projecting in V. tropica ) ( Fig. 4 ). Occasional individuals of the paper wasp Polistes sagittarius de Saussure, 1853 , have red at the apex of their first tergum. These may be confused with V. affinis , but Polistes tends to have red on the apex of the third metasomal tergum as well and to have more apically-contrasting orangish wings than V. affinis , in addition to differing in structure (see diagnosis of V. tropica below).

Materials examined. Singapore: 1 female (ZRC), coll. unknown, 1980 ; 1 female (ZRC), coll. unknown, 8 August 1981; 1 female (ZRC), coll. unknown, 1988; 2 females (IDL), Big Sister’s Island , coll. YGT, SXC, G. W. Yong, 9 December 2016 ; 1 female (IDL), Bukit Batok , coll. Y. T. Loh, 11 November 2018 ; 1 female (IDL), 115 Bukit Batok West Ave. 6, coll. F. Chuah, 13 Oct 2020 ; Bukit Timah Nature Reserve : 1 female (ZRC), coll. unknown, 14 July 1965; 1 female (ZRC), coll. H. K. Lua, 15 November 1990; 1 female (IDL), coll. Z. Y. Tan, 15 August 2015; Changi : 1 female (ZRC), coll. DHM, no date ; 1 female (IDL), coll. Y. G. Tan, 18 October 2015; 1 female (IDL), coll. W. H. Pang, 9 September 2017; 1 female (IDL), Changi Beach Park , coll. J. W. Tan, 10 September 2017 ; 1 female (IDL), Chestnut Forest , coll. Z. Y. Tan, 30 August 2015 ; Chinese Gardens: 1 female (IDL), coll. J. J. L. Lai, 26 August 2015, ex. Calliandra tergemina var. emarginata ; 1 female (IDL), coll. J. J. L. Lai, 14 October 2015, ex. Calliandra tergemina var. emarginata ; 1 female (IDL), coll. J. J. L. Lai, 19 October 2015, ex. Lagerstroemia speciosa ; 1 female (IDL), Choa Chu Kang , coll. Logaeswary S. R., 6 October 2017 ; 1 female (ZRC), Clementi , coll. Norani, 1 July 1985 , ex. Ficus sp. ; Coney Island : 1 female (IDL), coll. YGT, 29 September 2016 ; 1 female (IDL), coll. YGT, SXC, 12 October 2016 , ex. Premna sp. ; 2 females (IDL), coll. SXC, YGT, 27 October 2016 ; 1 female (IDL), Dover Forest , 7 September 2019 , S. Yau; 1 female (IDL), Elias Green, 13 August 2021, J. Soh; Gardens by the Bay: 1 female (IDL), coll. MSC, 14 July 2015 , ex. Hamelia patens ; 1 female (IDL), coll. MSC, 23 July 2015 , ex. Hamelia patens ; 1 female (IDL), coll. MSC, 14 September 2015 , ex. Hamelia patens ; 1 female (IDL), Green Corridor , King Albert Park, coll. M. J. Kong, 17 October 2015 ; 1 female (IDL), Green Corridor , old Bukit Timah railway station, coll. X. Y. Eyu, 10 October 2015 ; Holland Woods: 1 female (ZRC), coll. unknown, 1 October 2014; 1 female (IDL), coll. A. Q. E. Leong, 19 September 2017; 1 female (IDL), coll. E. Sivaprakasam, 19 September 2017; 1 female (IDL), 1 female (IDL), coll. C. Bayter, 19 September 2017; coll. H. X. Liew, 19 September 2017 ; 1 female (IDL), coll. J. K. H. Nai, 19 September 2017; 1 female (IDL), coll. J. Y. Chan, 19 September 2017; 1 female (IDL), coll. W. W. Wong, 19 September 2017; 1 female (IDL), coll. J. Y. Chan, 30 September 2017; 1 female (IDL), coll. JSA, 10 September 2019 ; 1 female (IDL), HortPark , coll. J. J. L. Lai, 9 November 2015 , ex. Aloysia virgata ; 1 female (IDL), Hwi Yoh Green Park , coll. J. Tan, 4 September 2021 ; Jurong Eco-Garden: 2 females (IDL), coll. A. Y. L. Teo, 5 October 2016; 1 female (IDL), coll. A. Y. L. Teo, 2 November 2016; 1 female (ZRC), Kay Siang Nursery , coll. unknown, 18 August 1982 , ex. Bauhinia sp. ; Kent Ridge: 1 female (ZRC), coll. unknown, 10 September 2000; 1 female (ZRC), coll. G. Cheng, 9 October 2000; Kent Ridge Park : 1 female (ZRC), coll. unknown, no date; 1 female (ZRC), coll. SL Tan, 10 September 2000; 1 female (ZRC), coll. unknown, 18 August 2001; 3 females (IDL), coll. LSM3265, 20 October 2015; 1 female (IDL), coll. SXC, G. W. J. Low, 21 October 2015 ; 1 female (IDL), coll. A. Tan, E. Tok, 30 August 2016; 1 female (IDL), coll. J. A. de Souza, 13 September 2016; 1 female (IDL), coll. LSM3265, 13 September 2016; 1 female (IDL), coll. P. E. Rayner, 24 October 2016; 1 female (IDL), coll. A. K. Koschmieder, 24 October 2017; 1 female (IDL), coll. D. L. Simons, 24 October 2017; 1 female (IDL), coll. D. Mathew, 24 October 2017; 1 female (IDL), coll. E. Håkansson, 24 October 2017; 1 female (IDL), coll. J. Y. Chan, 24 October 2017; 2 females (IDL), coll. unknown, 16 October 2018; 1 female (IDL), Khoo Teck Puat Hospital ; coll. MSC, 17 October 2015 , ex. Caesalpinia pulcherrima ; 1 female (IDL), Kranji Rail Corridor , coll. C. H. Tan, 28 August 2020 ; 2 females (IDL), Kusu Island , coll. SXC, YGT, 18 September 2016 ; Labrador Nature Reserve : 1 female (ZRC), coll. Mangrove Insect Project, 2 June 2016; 1 female (ZRC), coll. Mangrove Insect Project, 23 June 2016; 1 female (ZRC), Lakeside , coll. P. E. W. Tan, 13 April 1989 ; Lazarus Island , Main : 1 female (IDL), coll. W. J. Goh, J. H. Lim, 18 September 2016; 1 female (IDL), coll. W. J. Goh, J. H. Lim, 9 October 2016; 1 female (IDL), coll. J. Clerbois, 27 December 2017, ex. Caesalpinia pulcherrima ; 2 females (IDL), Lazarus Island , Seringat Island, coll. JSA, SXC, F. A. Tjong, C. N. Y. Ong, MSC, J. J. L. Lai, 15 August 2015 ; 2 females (IDL), Lim Chu Kang , coll. S. Yap, K. H. Pwa, Y. X. Tee, 20 September 2015 ; Lower Peirce : 1 female (ZRC), coll. O. Y. Kok, 16 December 1962; 1 female (ZRC), coll. O. Y. Kok, 30 December 1962; Mandai : 1 female (ZRC), coll. DHM, 20 November 1967 ; 1 female (ZRC), coll. DHM, 24 July 1976 ; 1 female (ZRC), Mount Faber , coll. J. Chai, 4 January 1985 ; NUS, Bukit Timah Campus: 1 female (ZRC), coll. O. Y. Kok, 15 May 1964; 1 female (ZRC), coll. unknown, 1 October 1965; NUS, Kent Ridge Campus: 1 female (ZRC), coll. unknown, 20 July 2012; 1 female (IDL), coll. J. Lim, 12 September 2015; NUS, Faculty of Arts and Social Sciences : 1 female (IDL), coll. MSC, 24 June 2015 , ex. Bidens pilosa ; 1 female (IDL), coll. J. K. Z. Phang, 24 August 2015; NUS, Faculty of Science : 1 female (IDL), coll. JSA, 26 September 2013 ; 1 female (IDL), coll. W. Y. Lee, 16 September 2015; 1 female (IDL), coll. K. N. J. Tan, 4 October 2015; 1 female (IDL), coll. Shivaram R., 5 September 2018; 1 female (IDL), NUS, Kent Vale Apartments , coll. JSA, 10 December 2018 ; 1 female (IDL), NUS, Lower Kent Ridge Road , coll. K. X. Toh, 10 October 2017 ; NUS, Ridge View Residences: 1 female (IDL), coll. S. X. E. Tang, 26 August 2015; 2 females (IDL), coll. T. K. Tan, 3 September 2015; NUS, School of Design and Environment : 1 female (IDL), coll. MSC, 14 July 2015 , ex. Asystasia gangetica ssp. micrantha ; 1 female (IDL), coll. MSC, 14 July 2015 , ex. Combretum indicum ; 1 female (IDL), coll. MSC, 23 July 2015 , ex. Bidens pilosa ; 1 female (IDL), coll. MSC, 26 August 2015 , ex. Bidens pilosa ; 1 female (IDL), coll. MSC, 21 September 2015 , ex. Waltheria indica ; 1 female (IDL), coll. MSC, 8 October 2015 , ex. Asystasia gangetica ssp. micrantha ; 1 female (IDL), coll. MSC, 19 October 2015 , ex. Bidens pilosa ; 2 females (IDL), coll. MSC, 18 November 2015 , ex. Bidens pilosa ; 1 female (IDL), NUS, sports field, coll. A. A. Q. Chan, 27 January 2016, ex. Syzygium pyrifolium ; NUS, University Hall : female (IDL), coll. S. H. Chua, 14 August 2014 ; 1 female (IDL), coll. E. S. See, 4 September 2015; 1 female (IDL), coll. J. Y. Chan, 4 September 2015; 1 female (IDL), coll. J. Goh, 18 September 2015; 1 female (IDL), coll. N. Lee, 8 October 2015; NUS, UTown: 1 female (IDL), coll. G. W. Yong, B. Lum, 17 August 2015; 1 female (IDL), coll. Z. Y. Tan, 17 September 2015; 1 female (IDL), Pandan Reservoir East , coll. S. Lehnert, 4 October 2018 ; Pasir Ris: 1 female (IDL), coll. S. Yap, K. H. Pwa, Y. X. Tee, 15 August 2015; 1 female (IDL), coll. M. D. Y. Khoo, 21 August 2015; 1 female (IDL), coll. Y. X. Tee, 4 September 2015; 1 female (IDL), coll. F. A. Tjong, 11 September 2015; 1 female (IDL), coll. H. H. J. Yeo, 29 August 2016; 1 female (IDL), coll. JSA, SXC, EJYS, 29 May 2014 ; Pasir Ris Park : 1 female (ZRC), coll. unknown, no date; 1 female (IDL), coll. JSA, SXC, EJYS, 29 May 2014 ; 1 female (IDL), coll. JSA, 2 June 2014 ; 2 females (IDL), coll. JSA, Z. W. W. Soh, 17 July 2014 ; 1 female (ZRC), Peirce area , coll. Lee Ping Yue, 18 October 1991 ; 1 female (IDL), Pulau Punggol Barat , coll. S. H. Ng, 20 October 2017 ; 1 female (IDL), Pulau Samulun , coll. Siti Aishah H., Hussin N., 30 August 2016 ; 2 females (IDL), Pulau Semakau , coll. JSA, J. Puniamoorthy, 24 October 2013 ; 11 females (ZRC), Pulau Semakau , mangroves, coll. Mangrove Insect Project, 4 April to 24 October 2013 ; 1 female (ZRC), Pulau Tekong , coll. DHM, 14 August 1976 ; Pulau Ubin: 1 female (IDL), coll. JSA, C. Dong, 28 July 2013 ; 1 female (IDL), coll. SXC, JSA, C. N. Y. Ong, F. A. Tjong, 3 September 2015 ; 2 females (IDL), coll. YGT, 21 September 2016 ; 1 female (IDL), coll. YGT, SXC, 5 October 2016 , ex. Syzygium sp. ; 1 female (IDL), coll. J. Ong, 1 November 2017; Pulau Ubin , Chek Jawa mangroves : 5 females (ZRC), coll. Mangrove Insect Project, 8 June to 1 November 2013; 4 females (ZRC), coll. Mangrove Insect Project, 10 May to 3 August 2016; 1 female (IDL), Punggol Waterway Park , coll. A. Y. L. Teo, 9 October 2016 ; Sembawang : 1 female (ZRC), coll. unknown, 20 October 1985; 1 female (IDL), coll. A. Y. L. Teo, 8 October 2016; 1 female (IDL), Sengkang , coll. C. H. Tan, 2017 ; 1 female (IDL), Sengkang Riverside Park , coll. A. Y. L. Teo, 9 October 2016 ; Sentosa : 1 female (IDL), coll. Z. H. Cheo, 30 August 2015; 2 females (IDL), coll. SXC, YGT, 28 September 2016 , ex. Scaevola taccada ; 1 female (IDL), 147 Serangoon North Avenue 1, coll. J. Tan, 4 September 2021 ; 1 female (IDL), coll. K. L. Ng, H. Y. Chew, S. L. Tay, 9 October 2016; 1 female (IDL), Springleaf Nature Park , coll. K. Seda, 26 June 2016 ; St. John’s Island : 4 females (IDL), coll. JSA, SXC, EJYS, K. Y. Ng, S. H. Chua, 8 September 2014 ; 2 females (IDL), coll. SXC, YGT, 18 September 2016 ; 1 female (IDL), coll. J. Clerbois, 2 December 2017, ex. Caesalpinia pulcherrima ; 1 female (ZRC), Sungei Buloh Wetland Reserve , coll. SBWR Volunteers, 12 July 2008 ; 1 female (ZRC), Tampines , coll. unknown, no date ; 1 female (IDL), Tampines Eco Green , coll. A. Y. L. Teo, 2 January 2017 ; 1 female (ZRC), Ulu Pandan , coll. S. K. Yeo, 1 December 1991 ; 1 female (IDL), Upper Bukit Timah Road , coll. D. Lim, 29 October 2015 ; 1 female (IDL), Upper Paya Lebar Road , coll. B. K. Y. Pua, 11 September 2015 ; 1 female (ZRC), West Coast , coll. unknown, 29 November 1987 , ex. Ixora sp. ; 1 female (IDL), Yishun NorthPark Residences , coll. Z. Y. Tan, 13 September 2021 .

Remarks. A common species found in all habitats and highly adapted to live near human dwellings, thus justifying Least Concern status by our criteria (see below). It is a generalist predator of other insects and can regularly be observed hunting flower-visiting bees and flies ( Fig. 3A ). Workers will also scavenge on carrion or food left behind by humans, and sometimes even insects trapped in spider webs ( Fig. 3B, C ). Like all wasps, they will also visit flowers for nectar ( Fig. 3D ). Nests are built from ground level to 30 m above ground in the tropics ( Chan, 1972; Matsuura, 1990). In our experience, nests are most commonly built between one and seven metres above ground, and may be constructed on vegetation or manmade structures ( Fig. 6A, B ). However, nests found low may have fallen from a height. The first author recorded three such cases in 2018 alone, where large mature nests originally situated at least five metres high fell into shrubs less than a metre above ground level, possibly following periods of heavy rain, and continued to survive and expand in their new locations. One such nest was examined at the natural end of the colony cycle; as it had fallen and landed on its side, new combs were built at a perpendicular angle to the original ones.

Nests are frequently polygynous in Singapore, founded by an average of three to five founding queens. The maximum number of queens we have recorded in a queen nest is 10, while up to 15 have been recorded in Papua New Guinea ( Spradbery, 1986). Further long-term investigations and monitoring are needed to determine the ratio of polygynous to monogynous nests as well as the rate of success and final nest and colony size for each group.

The embryo nest has a spherical or egg-shaped envelope consisting of a single continuous sheet, which is built and covers the comb fully very early in its development ( Fig. 6C ). Embryo nests founded by single queens develop a long tubular projection, or vestibule, which is a part of the singlelayered nest envelope itself. This points downwards and can reach the vertical length of the nest itself. The vestibule is removed upon the maturation of the first workers. As per our observations, nests with multiple queens do not develop a vestibule, with a large entrance hole at the bottom of the nest envelope replacing it ( Fig. 6D ). Upon maturation, the first workers remove the vestibule (in single-queen nests) and begin expanding the nest. In line with the expansion of the comb, the workers also expand and fortify the envelope, adding new material in small circular layers resembling overlapping scales, resulting in an imbricate (scalloped) pattern. The nest remains roughly spherical in shape initially but later grows pear-shaped, often with a rather abruptly truncate base in very large nests. This pear shape is in part due to the hypertrophy of the envelope above the combs into a prominent structure known as a roof cone. Nests of V. affinis and other aerial-nesting species such as V. analis and Vespa velutina Lepeletier, 1836 , only develop this tapering shape and roof cone in tropical regions; in sub-tropical regions, large nests of these species grow from spherical to taller than wide but retain a domed roof. We have not had the opportunity to dissect and examine the structure of a fully intact nest locally, but the interior of the roof cone has been described as having a cellular structure somewhat like the nests of some nasute termites, with a sponge-like mass of paper layers and air pockets ( van der Vecht, 1957; Starr & Jacobson, 1990). The exact function of the roof cone and why it is seen in tropical regions is uncertain, though van der Vecht (1957) opines that it is an adaptation to climatic conditions, specifically heavy tropical rains. There is usually only one entrance to the nest throughout its cycle; this is relocated from the bottom of the envelope to the side, and may be halfway or further up the nest wall in larger nests. Less commonly, large nests have more than one entrance. Nests in tropical regions including Singapore ( Starr & Jacobson, 1990; Martin, 1995; pers. obs.) can reach a metre or more in vertical length and width, with over 10 to 12 combs and over 10,000 to 14,000 cells and thousands of individuals at their peak.

This species and V. tropica in Singapore are likely models for the Batesian mimic Milesia vespoides Walker, 1857 , a large species of hoverfly ( Syrphidae ) that co-occurs in Singapore ( Fig. 7 ).

Floral associations. Aloysia virgate ; Antigonon leptopus ; Asystasia gangetica ssp. micrantha ; Averrhoa carambola ; Bauhinia sp. ; Bidens pilosa ; Caesalpinia pulcherrima ; Calliandra haematocephala ; Calliandra tergemina var. emarginata ; Callistemon citrinus ; Cocos nucifera ; Combretum indicum ; Ficus sp. , Hamelia patens ; Ixora sp. ; Lagerstroemia speciose ; Malvaviscus arboreus ; Mangifera indica ; Melaleuca viminalis ; Musa sp. ; Nephelium lappaceum ; Premna sp. ; Roystonea regia ; Scaevola taccada ; Syzygium pyrifolium ; Syzygium sp. ; Talipariti tiliaceum ; Waltheria indica .

Figures

Fig. 3. Vespa affinis in Singapore. A: worker capturing a flower-visiting sweat bee (Lasioglossum sp.); B: workers scavenging from a dead fish left behind at a fishing ground; C: worker with an insect caught in a spider’s web; D: worker nectaring from flowers of Leea rubra. (Photos: Lim Yu Jun, Marcus Ng and Zestin Soh).

Fig. 4. Comparison of the clypeus of Vespa affinis (A) and V. tropica (B). The white arrows point to the clypeal apices, bordering a medial emargination, which are semi-circular protuberances in V. affinis but more strongly produced as triangular projections in V. tropica. (Photographs: John Lee).

Fig. 6. Nests of Vespa affinis in Singapore. A & B, mature nest in a tree and on a metal beam of a plant nursery respectively, C, lateral view of an embryo nest, D, multiple queens in an early embryo nest. (Photographs: Kam-Yung Soh, John Lee, and Zestin Soh).

Fig. 7. The hoverfly Milesia vespoides, a Batesian mimic of Vespa affinis and V. tropica, at Windsor Nature Park in January 2022. (Photograph by Yue Teng Lee).