The first Dexiinae from Mauritius: the description of a new species of Pandelleia Villeneuve, 1907 (Diptera, Tachinidae)

A new species of the Afro‐Palearctic genus Pandelleia Villeneuve, 1907 (Diptera: Tachinidae), P. crosskeyi sp. nov., from Mauritius is described. This is the first Dexiinae to be described from Mauritius. In addition, this new species corresponds to the ninth species for this genus, and the third in the Afrotropics. The main external features that distinguish it from the other species in this genus is the abdomen that lacks the pair of small, round and dark brown spots, vein M ending in R4+5 at a 90° angle, and female with dark brown scutellum.


INTRODUCTION
Mauritius, along with the other main islands of Reunion and Rodrigues, compose the archipelago of Mascarenes. The history of Mauritius, similar to the islands of Réunion and Rodrigues, has been an endless series of ecological disasters and species extinctions (Thébaud et al., 2009); for instance, the extinct Dodo, the universal symbol of human-caused species extinction on islands, once lived on Mauritius. The highly endemic tachinid fauna of the region, currently listed among the world's top Biodiversity Hotspots (Thébaud et al., 2009), currently includes 15 species scattered among 11 genera of Tachinidae placed in Exoristinae or Tachininae (O'Hara et al., 2020), but none from the remaining subfamilies of Phasiinae or Dexiinae.
Pandelleia Villeneuve, 1907, is a Dexiinae genus with Afrotropical and Palearctic distribution, and it is currently placed in the tribe Dufouriini (Herting & Dely-Draskovits, 1993;O'Hara & Cerretti, 2016). Pandelleia is a poorly known genus, with some species being recognized only by the holotype. This genus includes eight species (Table 1), with P. sexpunctata (Pandellé, 1896) as type species. Mesnil (1975) revised the genus and provided a key to species in which he considered the Afrotropical Afrophasia, Curran, 1939 (now a synonym of Pandelleia), with the Palearctic species P. pschorni Mesnil, 1963, as a distinct genus. Mesnil stated that the study of Pandelleia is very difficult because the species are very rare and some are only known from males (e.g., P. ornata (Rohdendorf, 1923)), while others are known only from females (e.g., P. pilicauda Mesnil, 1975). The biology of the genus is little known, but some species have been recorded parasitizing species of Curculionidae (Crosskey, 1984;Thiem, 1922) and Chrysomelidae (Shima, 2015).
In the present study, we describe the first Dexiinae from Mauritius, a new species of Pandelleia previously identified and recognized as new by the late Dr. Roger Ward Crosskey. He left this undescribed species at the NHMUK collection. Furthermore, in his work on tachinids from tropical and southern Africa (Crosskey, 1984), he referred to this new species in a note in the key to Dufouriini genera: at the couplet for Pandelleia, one reads (Crosskey, 1984: 238): "Two species: also an undescribed species from Mauritius (…)". The Afrotropical Pandelleia now comprises three species.

MATERIAL AND METHODS
The type material is deposited at the Natural History Museum, London, United Kingdom (NHMUK). The labels of type material are represented with quotes (") to indicate the same label, slash (/) to line break, and semicolon to indicate a new label. Male and female terminalia were put into 10% solution of КОН for four minutes in boiling water, followed by neutralization in 5% acetic acid, and then cleared and washed with distilled water. The terminalia were examined on temporary slides with glycerin, and subsequently stored in plastic microvials with glycerin and attached to the respective specimen. The photographs were made by a digital camera Leica DFC420 attached to a stereomicroscope Leica MZ16. Images were captured with the software Leica LAS v4.1 and then stacked and scaled using the software Helicon Focus v5.3.14. Photographs were edited using the software Adobe Photoshop CS6, and line drawings were prepared and edited in Adobe Illustrator CS6. All plates were prepared in Adobe Illustrator CS6. The terminology of adult morphology followed Cumming & Wood (2017).

Pandelleia Villeneuve, 1907
Diagnosis: All the species hitherto known from Pandelleia are characterized by: body yellow to dark brown in ground color; arista pubescent; occiput, in both sexes, completely covered by black hair-like setae, except for P. dimorphia (Curran, 1939); anepimeral seta absent; vein M ending at R₄₊₅ and forming a sometimes long petiole; pair of small round dark brown spots on abdominal syntergite I + II, tergites III and IV, and sometimes on the V; females with the 6 th and 7 th segment tubular and anteriorly directed.
Abdomen (Figs. 1A, B): Short-ovate in shape. Mid-dorsal depression on syntergite I + II confined to about anterior ½. Syntergite I + II without setae. Tergite III with 1 lateral marginal and 1 median marginal pair of setae. Tergite IV with 1 or 2 lateral marginal and 1 median marginal pair of setae. Tergite V with a row of discal setae. Sternites visible from below. (Figs. 2A, B): Sternite 5 without transversal membranous band, weakly developed lobes and with setulae only on posterior margin. Sternite 6 symmetric. Tergite 6 completely fused with syntergosternite 7 + 8, with 1 long seta in the center and some setulae posteriorly; this complex is fused with epandrium, which is short and convex, with a visible suture line ( Fig. 2A). Ejaculatory apodeme small, rounded. Cerci broad, tapered and well separated in posterior view, curved, with the apex somewhat rounded and directed anteriorly, in lateral view. Surstyli narrow, strongly convex distally, slightly dilated, curved, and with tip narrowed internally in profile. Differ from male as follows: Dichoptic. Frons at its narrowest point about 2X as wide as vertex in dorsal view. Frontal vitta dark yellow. Fronto-orbital plate and occiput yellow. Parafacial, gena and face whitish. Antenna pale yellow, arista dark brown. Postpedicel with 0.24 mm in length. Gena with 0.16 mm in length. Palpus and labellum whitish to pale yellow. Thorax yellow, but scutum, scutellum, katatergite, anatergite and meron dark brown. Legs pale yellow, but tarsi (entirely) and mid and hind femur (distal ⅙) dark brown. Halter yellow. Abdomen yellow, but syntergite I + II with light brown thin band on posterior margin, tergites III and IV with larger band on posterior margin (¼ and ½, respectively), and tergite V with median dark brown vitta.
Etymology: Species named in honor of the late Dr. Roger Crosskey (1930Crosskey ( -2017, former curator of Diptera at the Natural History Museum in London, who first recognized this new species. Noun in genitive singular.
Finally, as a historical information, Dexia dejeanii Robineau-Desvoidy, 1830 would it be the first Dexiinae from Mauritius; however as its type is lost and it is currently considered an unplaced Tachinidae (O'Hara & Cerretti, 2016), Pandelleia crosskeyi is the only valid and recognized Dexiinae from Mauritius.

ACKNOWLEDGMENTS
We thank the Institute of Biosciences of the University of São Paulo for the logistical support. MDS is indebted to Nigel Wyatt (NHMUK) for facilities and kind assistance during his visit. Financial support from CAPES (MDS scholarship: 88882.333078/2019-01), CNPq (SSN research