Hoverflies of the Timon-David collection (Diptera, Syrphidae)

Abstract Background Hoverflies are among the most important insect pollinators and there is documented evidence of a recent decline in their populations. To trace the past distributions of hoverfly species, verified records of historical collections are essential. New information Here, we provide data on 1071 specimens of hoverflies collected or received by Jean Timon-David and hosted at the Marseille Natural History Museum, France. Most of the specimens were collected by Timon-David himself and come from south-eastern France, mainly from the Departments of Bouches-du-Rhône, Var and Hautes-Alpes. Most of these specimens were checked for the accuracy of their identification according to the latest identification keys. This resulted in 85 additions to the known fauna of the French Departments, mostly for Var and Bouches-du-Rhône. The taxonomy of all specimens was checked against the latest available checklists and updated names added whenever necessary. Specimens received from entomologists working in other continents may also be valuable, as these are historic testimonies of the fauna of their own respective regions of origin and may, therefore, also be used as reference material. One paratype specimen from Australia is present in the collection. The holotype of Cheilosia vangaveri Timon-David, 1937 is absent from the collection and should be considered as lost. All but two of the specimens with locality labels had their geographical coordinates of origin added in the dataset.


Introduction
Hoverflies (Diptera, Syrphidae) are known to be among the most important pollinators of flowering plants, along with Hymenoptera, Lepidoptera andColeoptera (Ssymank et al. 2008, Chisausky et al. 2020).The documentation of past distribution concerning these insects relies on existing collections, where the identification of specimens can be checked, in order to document changes in the distribution and relative abundance of the various species.
Professor J. Timon-David of Marseille" in his acknowledgements at the beginning of his monograph of the Bombylidae of the world alongside some the best known dipterists of the XX century "Dr.Willi Hennig , Dr. Erwin Lindner  and the late Professor Fred Keiser ".In addition to entomology, Jean Timon-David's work covered geology, biochemistry (his doctoral thesis was on insect fats), ichthyology, ornithology and, above all, parasitology.A tribute to his research in parasitology was published in 1968 in the Annales de Parasitologie (Dollfus 1968) and a scientific biography with a full bibliography was published in 1973 (Nicoli and Timon-David 1973).

Jean Timon-David's contribution to entomology
Jean Timon-David collected insects, mainly Diptera and Hymenoptera, from 1926 to 1961, and published pioneering research on the Diptera of the Mediterranean islands off the French coast (Van Gaver and Timon-David 1929a, Timon-David 1940Van Gaver and Timon-David 1929a, Timon-David 1940, Timon-David 1961), the high Alps (Van Gaver and Timon-David 1929b, Timon-David 1931, Timon-David 1937a, Timon-David 1937b), the Pyrenees (Timon-David 1949, Timon-David 1950) and the Sainte-Baume Massif (Timon-David 1936, Timon-David 1958).He also revised Diptera material from Morocco (Timon-David 1951a).Timon-David was a recognised specialist of Asilidae (Diptera) and his collection includes 18 boxes of material belonging to this family, with specimens from 13 different countries, including one box from the agricultural station at Boukoko (Oubangi-Chari, Central African Republic).He published an important series of revisions on the Asilidae of Madagascar (Timon-David 1951b, Timon-David 1952, Timon-David 1953a, Timon-David 1953b), with the description of several new species.One species of Asilidae from the Camargue was dedicated to him: Heteropogon timondavidi Tsacas 1970.
Indirectly, the labels of the specimens in his Syrphidae collection also show the regular contact he had with his foreign colleagues.For example, Ralph Leonard Coe (British Museum (Natural History)) identified some of his specimens.Timon-David received specimens from Charles Rungs (four Moroccan specimens), Frank M. Hull (U.S.A.), H.L. Lopes (Brazil), L. Richter (Colombia) and Edgar F. Riek (Australia).
As Nicoli and Timon-David (1973) point out, Jean Timon-David's collections from around Marseille date from a time when these areas were not yet fully urbanised.Thus, examination of this particular collection is a great opportunity for researchers to open a window into the past of this region which has since then been totally transformed and gives precious information about its environment which cannot be obtained by any other means.

General description
Purpose: The aim of this publication is to record all of the Syrphidae specimens hosted in the Timon-David collection at the Muséum d'Histoire Naturelle de Marseille (MHNM).
We also want to raise awareness of the entomological work of Jean Timon-David, whose publications, in French, were often in regional journals or conference proceedings and, therefore, difficult to access.In their recent synthesis of the Syrphid fauna of France, Speight et al. ( 2018) cite only one of Timon-David's publications, that of 1937 which contains the original description of Cheilosia vangaveri (Timon-David, 1937), named in honour of Ferdinand Van Gaver (1874-1943), the only colleague with whom Timon-David published on Syrphidae (Van Gaver and Timon-David 1928, Van Gaver and Timon-David 1929a, Van Gaver and Timon-David 1929b).A signed reprint of one of their joint publications (Van Gaver and Timon-David 1937) was given to the University Library (Fig. 2).The entomological collection of Jean Timon-David was given to the Muséum d'Histoire Naturelle de Marseille in 2006 by his son Pierre Timon-David.It contains a total of 114 boxes, including about ten thousand specimens.The aim of the present paper is to publish all the data on Syrphidae from this collection as a tribute to Jean Timon-David's outstanding work in entomology.
The identification of most specimens from France has been checked recently and the taxonomy of the whole collection has been brought up-to-date.

Project description
Title: Timon-David collection of Syrphidae (Diptera)

Sampling methods
Description: All available data on the 1071 hoverfly specimens present in the Timon-David collection in the Natural History Museum in Marseille were input in table format and made available on Zenodo (https://zenodo.org/doi/10.5281/zenodo.10362019).Labels of specimens collected by Jean Timon-David were always hand-written and usually mention the locality and a date, sometimes with the plant name on which the specimen was collected (Fig. 3).Jean Timon-David never put his own name on the specimen labels.
For most of the specimens, their identification was checked by Gabriel Nève (GN), Xavier Lair (XL) and Thomas Lebard (TL) and this is mentioned with the value 1 in the identificationVerificationStatus column, which is otherwise coded 0 for unchecked material.All label data from the Syrphidae specimens were input and most of the French specimens were re-identified according to recent revisions (e.g.Speight and Sarthou 2017, Speight and Langlois 2020, Speight et al. 2021).Latitudes and longitudes of all data from France were input using the topographical maps on the www.geoportail.gouv.frwebsite or printed 1/25000 maps of the studied areas.Data with label localities which corresponded to municipalities were input on the locality's centroid in latitude and longitude columns and their estimated uncertainty value (coordinateUncertaintyValue column) was set at 5000 metres.Data with more precise names were identified and input with an estimated uncertainty of 1000 metres.Data from countries other than France were usually far less precise; these were located using googleEarthPro and input with either a 5 km or 50 km uncertainty value.If a large administrative area only was mentioned on the label, such as Lafayette County, Miss., then a larger coordinate uncertainty was mentioned.Two locations could not be located and their coordinates are missing.If no location label was present under the specimen, verbatimLocality was given as missing data ("[non renseigné]").
The whole dataset was then formatted into a GBIF compatible file, which retains the original identifications, as well as the revised identification (if any).
In a few cases, the specimen could be identified only to a species group.This is indicated with "cf." in identificationQualifier column, with one species of the group mentioned in scientificName.In three cases, the identification was only possible within a pair of species and the two species were mentioned in identificationRemarks: Microdon mutabilis or Microdon myrmicae ( Schönrogge et al. 2002), Merodon moenium or Merodon avidus (Speight and Langlois 2020) and Cheilosia albitarsis or Cheilosia ranunculi (Doczkal 2000).
Step description: All data on specimen labels of the Timon-David Syrphidae collection were encoded in a table format.Every specimen received an individual label with its inventory Museum number.A total of 756 French hoverfly specimens were re-identified by GN, XL or TL.If the original identification had to be changed, the former identification was mentioned in the PreviousIdentification column and the updated one in the ScientificName column and the value in the identificationVerificationStatus column set as 1.The taxonomy of European species follows the list used by Vujić et al. (2022) for the Red List of European hoverflies.The taxonomy of specimens from other continents was checked with the Systema Dipterorum website (Evenhuis and Pape 2023).If the name had to be changed, but the identification of the specimen could not be checked, the updated name is mentioned in the scientificName column and a 0 value was put in the identificationVerificationStatus column.There is only one paratype in the whole collection: an Australian specimen of Sphiximorpha alaplicata ( Hardy 1945); in this case, typeStatus was set as "paratype" and its identificationVerificationStatus status was set as 1.
The type of Cheilosia vangaveri Timon-David, 1937 could not be located, despite Timon-David (1937a) mentioning specifically that the type remained in his collection.It was last seen in 1974 by E. Thorpe, but its subsequent whereabouts could not be traced (Barkalov and Ståhls 1997).Unfortunately, there is no surviving correspondence regarding Timon-David's collection which could help (P.Timon-David, pers. comm. 2023).
Occurrence remarks: Here, ecological data are indicated, if any (host plant, altitude or other information, such as a record number given by Timon-David, regarding the specimen).A total of 72 French specimen labels only include numbers and these were probably taken during Timon-David's studies on the islands of Marseille (Van Gaver and Timon-David 1929a, Timon-David 1940, Timon-David 1961) or the Alps (Timon-David 1937a); as their capture data are lacking, they could not be assigned to a specific location, only to France.

Number of Syrphidae in the
Number of Syrphidae from France in the Timon-David collection, by French Department.Coordinates: -36 and 53 Latitude; -123 and 151 Longitude.

Taxonomic coverage
Description: Specimens of 239 named species and of one named subspecies belonging to the family Syrphidae (Table 3).
Number of specimens by species in the Timon-David Syrphidae collection.

General discussion
The Syrphidae collected by Timon-David or received by him total 1071 specimens, mainly from France, but also from the Americas, Africa and Australia (Fig. 4).Unfortunately, the type specimen of Cheilosia vangaveri Timon-David 1937 could not be found in his collection.He probably lent it to a colleague whom we have been unable to identify.
Timon-David always retained a particular interest in the Sainte-Baume massif (Var), from which 155 hoverflies in his collection were collected between 1927and 1959(Timon-David 1936, Timon-David 1958).Another locality with a large number of collected specimens is his property at La Viste, a suburb of Marseille, with 118 records between 1926 and 1945.Timon-David left this property at the end of the 1940s when the northern motorway of Marseille was built.He then regularly visited the family property at Le Tholonet, near Aixen-Provence (32 records from 1941 to 1952) and, in particular, the hamlet of Bret, where he collected 25 specimens from 1950 to 1954.He was interested in the entomological fauna of the Marseille islands (Timon-David 1940, Timon-David 1961), where his data remain the only ones on Diptera.He always hunted by sight, using an entomological net, which explains the rarity of small species (genera Paragus, Orthonevra etc.) in his collection.
Some of the data from his collection have never been published and some of the specimens remained unidentified.We have now addressed this issue for all specimens originating from the Bouches-du-Rhône and Var Departments.His collection now contains 756 French specimens with reliable species identification labels.
The examination of this collection improves our knowledge of the distribution of French Syrphidae species.Compared with the most recent national database (Speight et al. 2018, Speight et al. 2020) and recent additions to departmental data (Nève 2018, Ropars et al. 2020, Lebard 2022, Solère et al. 2022), Timon-David's collection adds 34 species to the known hoverfly faunas of the Bouches-du-Rhône and 12 species to the Var Department, among others, leading to a total of 85 new Departmental hoverfly records (Table 4).Among the added species noteworthy is the oldest record of Merodon legionensis (Fig. 6) for France (Louboutin and Speight 2021).Timon-David's collection dataset will be used as one of the key sources for documenting the status of the south-eastern French hoverfly fauna present during the twentieth century, particularly in the Mediterranean area, with the hope that the recorded species will continue to thrive in the studied area.

Figure 2 .
Figure 2. Signatures of Jean Timon-David and Ferdinand Van Gaver on the cover of their joint 1937 publication (Van Gaver and Timon-David 1937), now in the Saint-Charles University Library, Aix Marseille University.
Timon-David collection, sorted by country of origin.Hoverflies of the Timon-David collection(Diptera, Syrphidae)

Figure 4 .
Figure 4. World distribution of hoverfly specimens in the collection of Jean Timon-David.

Figure 5 .
Figure 5. Distribution of French specimens of hoverflies in the collection of Jean Timon-David.

Figure 6 .
Figure 6.Habitus and details of head and abdomen of a specimen of Merodon legionensis collected at Bret, Le Tholonet, Bouches-du-Rhône, France, on 23 September 1951, the oldest French record of this species.
Hoverflies of the Timon-David collection (Diptera, Syrphidae) Hoverflies of the Timon-David collection (Diptera, Syrphidae) IP rights notes: This work is licensed under a Creative Commons Attribution (CC-BY) 4.0 Licence.All work derived from the present study should cite it appropriately, including the Museum where the material is held.
Character set: TimonDavidSyrphidaeColl_v01.csvData format: CSV (tab delimited values)Data format version: Darwin core, so that it could be transferred later into GBIF as more identifications are checked.Description:The dataset includes data on 1071 specimens of Syrphidae collected or received by Jean Timon-David, in GBIF compatible format.

Table 4 .
Additions to known French Departmental fauna.