Online citizen sciences reveal natural enemies and new occurrence data of Meteorusstellatus Fujie, Shimizu & Maeto, 2021 (Hymenoptera, Braconidae, Euphorinae)

Abstract Background Citizen science is a research approach that involves collaboration between professional scientists and non-professional volunteers. The utilisation of recent online citizen-science platforms (e.g. social networking services) has greatly revolutionised the accessibility of biodiversity data by providing opportunities for connecting professional and citizen scientists worldwide. Meteorusstellatus Fujie, Shimizu & Maeto, 2021 (Hymenoptera, Braconidae, Euphorinae) has been recorded from the Oriental Islands of Japan and known to be a gregarious endoparasitoid of two macro-sized sphingid moths of Macroglossum, Ma.passalus (Drury) and Ma.pyrrhosticta Butler. It constructs characteristic star-shaped communal cocoons, suspended by a long cable. Although M.stellatus has been reported only from the Oriental Islands of Japan, the authors recognise its occurrence and ecological data from Taiwan and the Palaearctic Island of Japan through posts on online citizen-science groups about Taiwanese Insects on Facebook and an article on a Japanese citizen-scientist's website. New information Through collaboration between professional and citizen scientists via social media (Facebook groups) and websites, the following new biodiversity and ecological data associated with M.stellatus are provided: Meteorusstellatus is recorded for the first time from Taiwan and the Palaearctic Region (Yakushima Is., Japan). Cechetraminor (Butler, 1875), Hippotioncelerio (Linnaeus, 1758) and Macroglossumsitiene (Walker, 1856) (Lepidoptera, Sphingidae) are recorded for the first time as hosts of M.stellatus and two of which (C.minor and H.celerio) represent the first genus-level host records for M.stellatus. Mesochorus sp. (Hymenoptera, Ichneumonidae), indeterminate species of Pteromalidae and Trichogrammatidae (Hymenoptera), are recognised as hyperparasitoid wasps of M.stellatus. Parapolybiavaria (Fabricius, 1787) (Hymenoptera, Vespidae) is reported as a predator of pendulous communal cocoons of M.stellatus. The nature of suspended large-sized communal cocoons of M.stellatus and the importance and limitations of digital occurrence data and online citizen science are briefly discussed.


Introduction
Citizen science is a research approach that involves collaboration between professional scientists and non-professional volunteers, aimed at enhancing the ability of scientific data collection and expanding its purview to scales or resolutions beyond the capabilities of individual researchers or research teams and has made significant contributions to science, education and society (e.g. Cohn (2008), Bonney et al. (2009), Silvertown (2009), Newman et al. (2012), Bonney et al. (2014), Kobori et al. (2016)). The recent rapid advancements in internet technology have considerably facilitated the active implementation of larger-scale online citizen-science projects across various fields of science (e.g. Dickinson et al. (2012), Kobori et al. (2016), Chandler et al. (2017), Kyba et al. (2023)). These projects utilise online platforms, such as social networking services (SNS) (e.g. Facebook, Instagram and Twitter) and specialised citizen-science applications (e.g. iNaturalist), surpassing previous citizen science in scope and magnitude.
For only professional scientists, it would be hardly possible to obtain comprehensive biodiversity data of hyper-diverse life on Earth. Biodiversity studies have, therefore, traditionally been supported by not only professional researchers, but also amateur citizen scientists. Natural history museums historically play a central role in supporting amateur scientists and developing citizen science up to date (Sforzi et al. 2018), but the communities on online platforms recently frequently take a similar role. The utilisation of online citizen-science platforms has greatly revolutionised the accessibility of biodiversity data by providing opportunities for connecting professional and citizen scientists worldwide. As a result, many new important discoveries and data have been published (e.g. Gonella et al. (2015), Jaume-Schinkel et al. (2020), Santamaria et al. (2020), Zhang et al. (2022)).  is a recently described braconid parasitoid wasp species of the M. pulchricornis clade from the Oriental Region, Ryukyu Islands, Japan . It has been known to be a gregarious endoparasitoid of two macro-sized sphingid moths of Macroglossum, Ma. passalus (Drury) and Ma. pyrrhosticta Butler . One of the most interesting features of M. stellatus is its characteristic star-shaped communal cocoons, suspended by a long cable.  suggested that this unique cocoon morphology likely contributes to reducing the risk of hyperparasitism by minimising the exposed area of each individual cocoon as observed in the microgastrine gregarious braconid parasitoid Cotesia glomerata (Linnaeus) (Tagawa andFukushima 1993, Tanaka andOhsaki 2006).

Meteorus stellatus
Although M. stellatus has been reported only from the Oriental Islands of Japan, the authors recognise its occurrence and ecological data from Taiwan and the Palaearctic Island of Japan through posts on online citizen-science groups about Taiwanese Insects on Facebook and an article on a Japanese citizen-scientist's website. Therefore, the authors conducted an online citizen science-based investigation on M. stellatus via social media and the present paper aims to record M. stellatus from these regions for the first time, to report some new ecological data associated with it and to re-evaluate the function of the characteristic cocoon.

Online data compilation
All digital occurrence data of M. stellatus were manually compiled from three online citizenscience groups of Taiwanese insects on Facebook (Table 1) and an article on a Japanese citizen scientist's website without automated web crawler programmes. The data were searched by specific keywords, such as "懸繭蜂" (the common Chinese name for the genus Meteorus) and "Meteorus." We tried to contact all the posters to obtain permission to reuse and edit their digital occurrence data of M. stellatus, including the original resolution photographs and to gather additional relevant information through communication with them. The data which failed to obtain a poster's response to our permission offer were excluded from our results in accordance with ethical considerations. All the obtained digital occurrence data were shown as figures and summarised as tables in the present paper since the original posts and links are probably not permanent.

Identification of digital occurrence data
The compiled digital occurrence data of M. stellatus and related insects (i.e. hosts, hyperparasitoids and predators) were initially identified, based on images or movies. Subsequently, identification was confirmed by morphological observation of specimens using a stereoscopic microscope (SMZ1500, Nikon, Tokyo, Japan) if the original samples were available. Examined specimens were mounted and preserved in public institutions (Table 2).

Figure editing
The habitus of M. stellatus was newly photographed for the present paper with the technique described by  and . Original Table 1.
A list of online citizen-science groups on Facebook focused on Taiwanese insects. These groups were utilised to compile digital occurrence data of M. stellatus from Taiwan. The number of group members was verified on 26 January 2023.

Diagnosis
See the "Taxon treatment" section of .

Occurrence data of M. stellatus
A total of 25 digital occurrence data of M. stellatus were compiled. Twenty-two of them were permitted by the posters for reuse of their data in the present paper (Table 3), while three were not. Amongst the permitted data, 21 were obtained from the Taiwanese Facebook posts, representing the first record of M. stellatus from Taiwan (Table 3; Figs 1, 2, 3, 4, 5, 6, 7, 8, 9, 10). One digital occurrence record was recognised from Yakushima Is. Japan, via the Japanese website, representing the first record of M. stellatus from the Eastern Palaearctic Region (Table 3; Fig. 11). The suspended communal cocoons were observed in all compiled data (Table 3), but larval and adult stages were not. In addition, associated insects with M. stellatus were recognised in 11 of the 22 permitted digital occurrence data (50% of all data) (see Table 3 and the below "Insects associated with M. stellatus" section).  Fig. 4b n/a n/a n/a g TW n/a Fig. 4a n/a n/a n/a    Fig. 4i-k n/a n/a n/a i TW n/a Fig. 4f,g n/a n/a n/a j TW n/a Fig. 4c n/a n/a n/a k TW n/a Fig. 10 n/a n/a n/a n/a o TW n/a Youtube n/a n/a Youtube p TW n/a Fig. 4d n/a n/a n/a q JP Fig. 11b,c Fig. 11a,b n/a n/a n/a r TW Fig. 7d n/a n/a n/a       Seven physical occurrence data were also listed in the present paper (Table 4; Figs 2, 12). Four of them were based on voucher-preserved specimens for digital occurrence data, while the remaining three were recognised through investigation of a Hymenoptera collection preserved at TARI by HPC and KTL.

ID Locality Adult Cocoon Host Parasitoid Predator
w TW n/a NMNS n/a n/a n/a x TW n/a NMNS n/a n/a n/a y TW TARI n/a n/a n/a n/a z TW TARI; Fig. 12a n/a n/a n/a n/a aa TW n/a TARI; Fig. 12c n/a n/a n/a ab TW TARI; Fig. 2 n/a n/a n/a n/a ac JP KPM KPM n/a n/a n/a

Insects associated with M. stellatus
A total of 12 insect taxa were recognised as being associated with M. stellatus (Table 5) (including the data from ).    Table 5.
Hosts: A total of five host species from three hawk moth genera (Lepidoptera, Sphingidae: Cechetra, Hippotion and Macroglossum) were listed in Table 5. Three of which (C. minor, H. celerio and Ma. sitiene) were recorded for the first time as hosts. The majority of moth species currently recognised as hosts belong to the genus Macroglossum. On the other hand, two host moth species belong to the genera Cechetra and Hippotion, representing the first genus-level host records for M. stellatus.
As hosts of M. stellatus, three (C. minor, H. celerio and Ma. sitiene) were known only from Taiwan (present paper), one (Ma. passalus) was from both Taiwan (present paper) and Japan ) and one (Ma. pyrrhosticta) was only from Japan .
Hyperparasitoids: A total of six hyperparasitoid wasps, including three new data from Taiwan, were listed in Table 5. However, two of the new data could unfortunately not be identified as generic-and species-levels and were excluded from the "Taxon treatments" section in the present paper, while their higher classification (indeterminate species of Pteromalidae and Trichogrammatidae families) was mentioned in the "occurrenceRemarks" of M. stellatus and Table 5. The remaining new hyperparasitoid wasp data were identified as the Darwin wasp genus Mesochorus (Ichneumonidae, Mesochorinae), but the specific name could not be identified.

Predators:
Only one paper wasp species, Parapolybia varia (Fabricius, 1787) (Hymenoptera, Vespidae), was recognised as a predator (Table 5; Fig. 10). It was recognised from two sources ( Table 3). The cocoon of M. stellatus was intensively attacked by either a single worker (Fig. 10) or many workers (as seen in the video at https://www.youtube.com/watch?v=AYzqgeJwxOo). The communal cocoon, suspended by a long cable, was moderately to strongly swaying and spinning due to natural winds and the flapping of the paper wasps' wings. First, the paper wasps were hovering in the air and trying to figure out the optimal timing for landing on the cocoon. Subsequently, they landed on the cocoon if it was relatively stable, but gave up landing on it if it was unstable.

Taxon discussion
The larva of this species was identified, based on Chen (1994) and Wang (1995).

Notes
Newly recognised as a host of M. stellatus.

Taxon discussion
The larva of this species was identified, based on Chen (1994) and Wang (1995).

Notes
Newly recognised as a host of M. stellatus.

Taxon discussion
The larva of this species was identified, based on Chen (1994) and Wang (1995).

Notes
Known as a host of M. stellatus from Japan ) and Taiwan (present paper).

Taxon discussion
The larva of this species was identified, based on Chen (1994) and Wang (1995).

Taxon discussion
Although preserved specimens were unavailable and these paper wasps sometimes exhibit a wide range of colour variations (van der Vecht 1966), the available characters, based on photographs and movies, matched well with the diagnostic characters for this species listed by Yamane and Wang (1996) and .

Ecology
This genus is known to be hyperparasitoids of other parasitoid wasps, including Meteorus species (Yu et al. 2016). Adult wasps examined in the present study emerged from the cocoon of M. stellatus.

Taxon discussion
Preserved specimens were identified as belonging to this genus, based on the key provided by Araujo et al. (2018).

Discussion
Previous host data of M. stellatus suggested that its primary host consists of sphingid moth species of the genus Macroglossum ). However, our new data indicate that M. stellatus parasitises not only Macroglossum species, but also species of other genera of the tribe Macroglossini, implying polyphagous nature, as well-known and extensively studied in an extremely polyphagous koinobiont endoparasitoid M. pulchricornis that has more primitive lineage than M. stellatus of the M. pulchricornis clade  and employs virus-like particles (VLPs) to prevent host granulocytes (Suzuki and Tanaka 2006, Suzuki et al. 2008, Suzuki et al. 2009, Yokoi et al. 2017, Maeto 2018. The geographic distribution of these hosts is wider than the currently-known range of M. stellatus, suggesting that M. stellatus is also potentially distributed in a wider area (e.g. China and the Philippines). Our data suggest that M. stellatus is predominantly distributed in the subtropical Oriental Region of the Far East and at least in the southern area of the Palaearctic Region. However, our interest is in their true northernmost range because one of their host species (Ma. pyrrhosticta) is also distributed in the subarctic Hokkaido in Japan. Although current data on M. stellatus are insufficient to understand the true host range, their parasitoid mechanisms and strategies and distribution, we will possibly be able to reveal their comprehensive biology through continued data collection and collaboration with citizen scientists via social media.
The pendulous communal cocoons of M. stellatus are occasionally attacked by the social wasp predator, P. varia, intensively. According to Starr (1992), the local abundance of P. varia in Taiwan is highly variable. Therefore, the strength of the local predation pressure of M. stellatus may be similarly variable depending on the local abundance of P. varia. As ecological data for P. varia is still poor and incomplete (e.g. van der Vecht (1966)), these data on the predation behaviour of P. varia could be important knowledge for understanding the biology of not only M. stellatus, but also P. varia.
The suspension of the cocoon by a cable has been considered to make the pupating wasp inaccessible to certain potential enemies (Shaw and Huddleston 1991, Zitani and Shaw 2002, Zitani 2003, Quicke et al. 2006, Shirai and Maeto 2009, Maeto 2018. However, intensive attacks on the suspended cocoon of M. stellatus by P. varia suggest that the suspended large cocoon may attract the attention of enemies, thereby probably increasing the risk of attack by predators with strong mandibles (or beaks) and high flight ability. In particular, large communal cocoons provide a stable foothold to relatively large-sized enemies, such as paper wasps, while small solitary cocoons do not. On the other hand, as we observed, the suspended communal cocoon was moderately to strongly swaying and spinning due to natural winds and the flapping of the paper wasps' wings, sometimes resulting in the paper wasps giving up landing and attacking it if it was unstable. These factors suggest that the function and evolution of the long cable and the communal cocoons are more complicated than previously hypothesised. Therefore, as a step towards understanding it, the relationships between the cable length and the cocoons' size and the impact of the intensive attacks by P. varia and other enemies, including hyperparasitoids, should be evaluated in future studies.
All data of M. stellatus observed in the present study were based on cocoons and the majority of it was recorded before being described as the new species. This suggests that their communal star-shaped cocoon suspended by a significantly long cable would have likely caught the interest of not only natural enemies, as suggested above, but also many citizen scientists. In contrast, relatively fewer data for adults from social media suggest that the small body size makes citizen scientists difficult to find them. In addition, the lack of uniqueness of adult morphology may not attract interest from citizen scientists. Therefore, social media posts are valuable for understanding biodiversity and natural history, but artificial biases should always be considered when we use such data.
One of the most interesting and important features of parasitoid wasps is their tremendous diversification through the evolution of interaction between the wasps and their hosts. As recently highlighted in Darwin wasps (Klopfstein et al. 2019), the number of professional scientists of parasitoid wasps is insufficient to fully reveal their biodiversity and evolutionary history. Therefore both wasps' and hosts' data are still scarce. However, much biodiversity and natural history data can now be found by the contribution of citizen scientists on social media platforms, as demonstrated in the present study. Consequently, the biodiversity and evolutionary history of parasitoid wasps may be significantly uncovered by compiling and analysing such data. Furthermore, many scientifically interesting and important data have been shared on social media by citizen scientists, but most of them have never been published in scientific publications. Therefore, professional researchers should continue to monitor social media posts and maintain positive relationships with citizen scientists and should investigate and publish scientifically valuable information found on social media to contribute to revealing biodiversity and the evolution of life on Earth.