Research Article |
Corresponding author: John Smit ( john.smit@naturalis.nl ) Academic editor: Ximo Mengual
© 2020 John Smit, Theo Zeegers, Phurpa Dorji.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Smit J, Zeegers T, Dorji P (2020) A new species of Eumerus (Diptera, Syrphidae) from the Kingdom of Bhutan, the easternmost representative of the bactrianus subgroup. ZooKeys 906: 141-151. https://doi.org/10.3897/zookeys.906.48501
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A new species of Eumerus, Eumerus druk Smit sp. nov., is described from Bhutan. This species belongs to the bactrianus subgroup of the strigatus species group. Seven species are currently known within this subgroup: four European, one of which is also found in the Near East, and three more only known from Tajikistan. The new species extends this disjunct distribution to the east by at least 2,000 km, stretching far beyond the reported Turano-Mediterranean region and into the Himalayas. A diagnosis and a key to all Central and Eastern Palaearctic species of the Eumerus bactrianus subgroup are provided.
Central Palaearctic, Eastern Palaearctic, flower flies, hover flies, Himalaya, identification key
Hover flies are often large and attractively coloured insects that are frequently found on flowers and play a vital role in ecosystem services as pollinators (
This new species was collected during an expedition in spring 2018 as part of the Bhutan Biodiversity Project. This project is a cooperation between the National Biodiversity Center (Bhutan), Naturalis Biodiversity Center (Netherlands), and five other Bhutanese organizations aiming to generate knowledge on Bhutanese invertebrates. The main goal was to make a survey of several invertebrate groups and make this knowledge available through publications and field guides.
Material from the following collections has been studied or is deposited therein, introducing the abbreviations: National Biodiversity Center, Thimphu, Bhutan (
The Eumerus strigatus group was first defined by
The Eumerus bactrianus subgroup within the strigatus group was defined by
The bactrianus subgroup is represented by four Western Palaeartic species (i.e., E. banaticus Nedeljković, Grković & Vujić, 2019, E. bicornis Grković, Vujić & Hayat, 2019, E. bifurcatus van Steenis & Hauser, 2019, and E. pannonicus), three Central Palaearctic species described from the Hissor Mountains in Tajikistan (
The Palaearctic Region can be divided into subregions.
Paratype Tajikistan • male; у. Копдара 1100 m, д. ВарзобаТадж., Гуссаковский [Kopdara 1100 m, d. VarzobaTadž., Gussakovskii]; 15 May [19]39 (
Body golden- or bronze-green, often with purple tinge. Legs bronze-green, tip of femora and basal third of tibia as well as tarsomeres 1–4 brightly brownish yellow, apical tarsal segment dark. Metaleg with basotarsomere expanded and short, as longs as second and third segment combined. Basoflagellomere trapezoid (Fig.
Bhutan, Thimphu.
Body golden-coppery, except t2 and t3 medially and t4 basomedially: shiny black amplified by short adpressed black pile. Basoflagellomere rectangular, with a rounded posterior corner. Male: abdomen t3 and t4 laterally with long, silvery, ventrally directed pile; s4 without an incision posteriomedially but medial part of sternite less sclerotized. Basotarsomere of metaleg simple, equal in length to the rest of the tarsomeres. Male terminalia: posterior surstyle lobe with a tuft of long pili just anterior to the bifurcation.
Male. Length of body (excluding antennae) 7.5–8.5 mm, length of the wing 5.5–6.5 mm. Head. Eyes holoptic, eye contiguity 9–10 ommatidia long, ommatidia near eye contiguity conspicuously larger than those in the posterior part (Fig.
Eumerus druk Smit, sp. nov., male holotype A epandrium, lateral view B surstyle lobe, ventral view C hypandium, lateral view D hypandrium, ventral view E fourth sternum. Eumerus bactrianus Stackelberg, 1952, male F antenna, lateral view. Eumerus druk sp. nov. G antenna, lateral view. Eumerus turanicola Stackelberg, 1952, male H antenna, lateral view, after (
Thorax. Entirely shiny black, with golden luster (Fig.
Abdomen. Entirely black, parallel sided, t2–4 with oblique maculae of white pollinosity, those on t3 and t4 longer and clearly lunulate (Fig.
Terminalia
(Fig.
Similar to male except for the normal sexual dimorphism (Fig.
The specific epithet ‘druk’ is Dzongkha (the Sino-Tibetan language spoken in Bhutan) for dragon and refers to the official name of the kingdom: Druk yul (country of the Dragon people, or the Land of the Thunder Dragon). It should be treated as a noun in apposition.
This species is only known from the type series collected at the Royal Botanical Garden in Thimphu, Bhutan, but it likely has a wider distribution in the Himalayas. This is the only Eastern Palaearctic species of the bactrianus subgroup of the strigatus species group.
Type material. Holotype Bhutan • male; Thimphu, Royal Botanical garden; 27.425N, 89.650E, 2400 m a.s.l.; 26 April 2018; J.T. Smit & Th. Zeegers leg.; RMNH.INS1092470.
Paratypes Bhutan • 4 males; same collection data as for holotype • 1 female; same data as for holotype; RMNH.INS1092471.
The holotype is in good condition and is deposited, together with one male and female paratype in the National Biodiversity Center, Bhutan (
The male of Eumerus druk Smit, sp. nov. is easily distinguished from all other species in the bactrianus subgroup by the long, silvery, ventrally directed, pile on the lateral sides of t3 and t4. Eumerus banaticus has some longer pile on the lateral sides of t4, but this is shorter, not ventrally directed, and not present on t3. Furthermore E. banaticus is easily distinguished by the lack of pollinose maculae on t4 and by the shape of st4 and the terminalia. Eumerus hungaricus Szilády, 1940 and E. pulchellus Loew, 1848, which have similar long, ventrally directed pile on t3 and t4, are superficially similar but the pile is much more dense. Eumerus druk Smit sp. nov. can easily be distinguished by the bifurcate posterior surstyle lobe. E. hungaricus and E. pulchellus furthermore lack the golden-coppery luster on the thorax and abdomen of E. druk. Eumerus pulchellus is a more slender built species, with a more bluish luster, a relatively slender metafemur, the pro- and mesotarsi predominantly light brown, the basoflagellomere orange. Eumerus hungaricus is a more black species with less luster, especially on the abdomen, which is predominantly black pilose; s3 is very slender, about 2.5 times longer than wide, and t4 has a yellow posterior margin, medially.
(based on
(based on
1 | All tarsi entirely black. Basoflagellomere rectangular (Fig. |
E. druk Smit, sp. nov. |
– | Tarsi predominantly reddish-yellow. Basoflagellomere trapezoid, oval or triangular shaped. Abdomen with t2–4 with the same bronze-green luster as laterally. Male: s4 with a clear incision posteromedially and posterior surstyle lobe lacking the tuft of long pili prior to the bifurcation | 2 |
2 | Basoflagellomere trapezoid (Fig. |
E. bactrianus Stackelberg |
– | Basoflagellomere not trapezoid but oval or triangular. s4 with a deep, angular incision posteriomedially | 3 |
3 | Basoflagellomere triangular (Fig. |
E. turanicola Stackelberg |
– | Basoflagellomere oval (Fig. |
E. turanicus Stackelberg |
Naturalis Biodiversity Center, Leiden and the Uyttenboogaart-Eliasen stichting are kindly thanked for their financial support of the collecting trip for JS (SUB.2017.12.07) and TZ (SUB.2017.12.06). We thank Dr. Tashi Yangzome Dorji, Program Director National Biodiversity Centre, Ministry of Agriculture and Forests, Choki Gyeltshen from the National Biodiversity Center, Bhutan and Tshelthrim Zangpo Plant Protection Officer, Entomology for their support with permits, logistics, and help in the field. We thank Jeroen van Steenis for providing the male paratype of Eumerus bactrianus held in