Provespa Ashmead, 1903

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 : 458-461

Provespa Ashmead, 1903 Provespa anomala (de Saussure, 1854)

Anomalous Night Hornet ( Fig. 1 )

Vespa anomala de Saussure, 1854: 112 .

Global distribution. Brunei, Indonesia (Sumatra, Bangka, Batu Island, Kalimantan, Laut Island, Riau Islands); Malaysia (Peninsular, Langkawi, Sabah, Sarawak); Singapore; Thailand (Peninsular).

Diagnosis. More slender than hornets in the genus Vespa . Ground colour orange to light brown ( Fig. 1 ). Wings amber. Provespa nocturna found in adjacent countries has the female clypeal margin more deeply emarginate, whereas P. barthelemyi of continental Southeast Asia has a shorter first gastral segment and a paler clypeus (females) and antennae with tyloids (males).

Materials examined. 1 female (ZRC), Singapore, coll. unknown, 2 July 1967 ; Bukit Timah Nature Reserve : 1 female (ZRC), coll. DHM, 3 December 1974 ; 1 female (ZRC), coll. H. K. Lua, 8 October 1989; 2 females (ZRC), coll. H. K. Lua, 24 October 1989; 2 females (ZRC), coll. Y. H. Koo, 13 December 1989; 1 male (ZRC), coll. C. M. Yang, 8 May 1990; 2 females (ZRC), coll. Z. Chen, 13 May 2009; 15 females (ZRC), coll. Mangrove Insect Project, 1 February to 11 October 2017; 1 female (ZRC), coll. JXQL, 28 February 2010 ; 1 male (IDL), Chestnut Avenue 1, coll. N. Puniamoorthy, 20 April 2018 ; 14 females (IDL), Chestnut Forest , coll. JXQL, LFC, EJYS, 11 June 2014 ; Island Club Road: 4 females (ZRC), coll. T. W. Koh et al., 7 May 1993; 1 female (IDL), coll. L. Y. Tan, 7 October 2013; 1 female (ZRC), Kent Ridge , coll. T. L. Ng, 10 September 2000 ; 7 females (ZRC), Lower Peirce , coll. KLY et al., 4 June 1992 ; 1 female (IDL), Mandai Road , coll. W. Y. Toh, 4 November 2021 ; 1 male (IDL) Meadow Condominium @ Peirce, Upper Thomson Rd., 1 September 2018 , coll. A. J. K. Teo; Nee Soon Swamp Forest : 4 females and 1 male (ZRC), coll. KLY et al., 22 May 1992 ; 2 females (ZRC), coll. KLY et al., 28 May 1992 ; 4 females (ZRC), coll. Mangrove Insect Project, 3 December 2014 to 1 April 2015; 1 male (IDL), Peirce area , coll. A. J. K. Teo, 1 September 2018 ; 1 female (ZRC), Pulau Tekong , coll. C. S. Tang, 3 July 2000 ; 1 female (IDL), Rail Corridor , coll. Z. H. T., 15 Oct 2021 ; Sime Track: 1 female (ZRC), coll. T. W. Koh et al., 7 May 1993; 1 female (IDL), coll. M. K. Tan, H. Yeo, 30 June 2013; 1 female (IDL), 143 Thomson Ridge Estate , coll. C. Sih, 24 Aug 2019 ; Tu Fu Avenue , coll. W. M. Lim, 20 August 2015 ; Upper Seletar Reservoir : 1 female (ZRC), coll. JXQL, 13 February 2010 ; 1 female (ZRC), coll. JXQL, 22 September 2011 ; 1 female (IDL), Venus Drive , coll. W. S. Hwang, 20 February 2014 .

Remarks. A forest-associated species, mostly recorded in and near the Central Catchment Nature Reserve but also reported from Kent Ridge (only one record of seven individuals despite high observer coverage of the NUS campus and vicinity) and Pulau Tekong. Its occurrence at relatively few sites in or near high-quality forest habitat justifies Near Threatened status by our criteria (see below). Both individuals and nest-founding swarms are routinely attracted to artificial light sources ( van der Vecht, 1957; Matsuura, 1999; pers. obs.) and may inadvertently enter houses and outdoor buildings at night ( Sharma, 1973; pers. obs.), or visit light traps for moths ( Fig. 1B ). In the day, individuals may commonly be found resting under shelters or on the walls of public lavatories located in the vicinity of forested areas where it occurs, presumably unable to find their way out after being attracted to the lights at night ( Fig 1A ). Photographs and a description of a nest in the Central Catchment Nature Reserve that had apparently fallen from its original location are provided in Ngiam et al. (2017), and a 2021 observation of a nest in an unspecified location in Upper Seletar Reservoir Park was recorded on the community science portal iNaturalist (https://www.inaturalist. org/observations/82994817). Beyond Singapore, nesting habits and nesting structure of this species are described in detail in Maschwitz & Hänel (1987), Matsuura & Yamane (1990), and Matsuura (1991, 1999). In these accounts, the initial nest is described as egg-shaped with a diameter of four to eight cm, with one or two combs covered with two or three layers of envelope, and only one small exit at the bottom with a diameter of eight mm. Mature nests are also subglobular with a diameter of approximately 20 cm. There are four to six combs covered with an envelope consisting of three to five layers, and a single entrance located laterally in the middle or slightly towards the bottom of the nest. The nest envelope is said to have excellent waterproof characteristics and to be stronger than that of any Vespa species, and the combs are also stronger than those of any other vespine genera. The envelope and cell walls are much thicker, stronger, more flexible and fibered than in nests of the other three vespine genera, and is uniformly brown or greyish-brown without the patterns on the nests of Vespa . Dead banana leaves and similar materials rich in fibrous tissue are used as nesting material. Nests are commonly built close to the ground ( Martin, 1995) at heights ranging from 10 to 30 cm above ground ( Matsuura & Yamane, 1990; Archer, 2008, but sometimes are over 10 m above ground in trees. Though usually built in trees, nests may occasionally be found in enclosed cavities ( Matsuura, 1991; Martin, 1995).

Provespa species are known to be swarm founders; a group of workers leaves with a fertilised new queen (rarely two) to start a new nest. The first author once observed a swarm settling down under the roof of a wooden shelter at Hindhede Nature Park, probably as a temporary resting location rather than a potential nest site ( Fig. 1C ). On a subsequent visit a week later, the swarm had moved to another corner of the shelter and split into two groups, one smaller and one larger. One week after this, the wasps were all gone. Matsuura (1991) states that swarming colonies of Provespa species sometimes trespass into houses through open windows at night, attracted by lamp light, and are thus regarded as a nuisance in parts of their range. Details of the ‘swarmfounding’ behaviour of this species in Sumatra are described in Matsuura (1999); ten swarms recorded consisted of 43 to 128 workers (55 on average) and eight had only one queen, while two had two queens.

Little is known of its feeding habits, but van der Vecht (1957) cited the observation in Palembang, Sumatra during the Second World War by C. J. H. Franssen that P. anomala workers attacked bluebottle flies around latrines at night. Maschwitz & Hänel (1987) also note that the species preys on moths at light traps. At light traps in Singapore, individuals have been observed carrying various unidentifiable prey insects, mostly Diptera or Hymenoptera , though the actual act of capturing the prey was not seen ( Fig. 1B ). Aberrant activity during daytime was noted by the first author in March 2010, where an individual landed on the ground in the daytime to feed on belachan (shrimp paste) mixed into the ground as a bait for butterflies ( Fig. 1D ).

This wide-ranging Sundaic species is the only Provespa species known from Singapore, but Provespa nocturna van der Vecht, 1935 , has been recorded from nearby “ Riau ” in Indonesia ( Archer, 2012). However, Provespa we have seen from the Riau Islands are P. anomala , so night hornets should be identified critically.

Figures

Fig. 1. Provespa anomala in Singapore. A, worker resting in a public lavatory in a forested park; B, worker capturing a small insect at a light trap at night; C, a swarm congregating under a shelter in a probable swarm-founding event; D, unusual occurrence of a worker attracted to shrimp paste in the day. (Photos: Marcus Ng, John Lee).