A striking new species of Dolichomitus Smith, 1877 (Hymenoptera: Ichneumonidae; Pimplinae) from South America

Abstract Background Dolichomitus Smith, 1877 is a genus of Darwin wasps characterised by their large bodies and long ovipositors, that includes more than 75 species worldwide, 20 of which occur in the Neotropical Region. Due to recent efforts, the number of species of this genus continues to increase in South America. New information A new iridescent species of Pimplinae, Dolichomitus meii sp. nov., is described and illustrated. It was discovered from the biological station of Yanayacu located in the north-eastern slopes of the tropical Andes. It may be separated from all other species of Dolichomitus Smith by the striking colour pattern and apically strongly decurved ovipositor.


Introduction
Dolichomitus Smith is a widespread genus of pimpline Darwin wasps, represented in the Neotropical Region by 20 described species (Yu et al. 2016, Araujo et al. 2020. The tropical species of the genus are moderately large (fore wing length from 5.0 to 22.0 mm), vividly coloured and possess long ovipositors (Gauld 1991, da Silva Loffredo and Penteado-Dias 2012, Araujo et al. 2020. These characteristics make them especially conspicuous amongst the tropical Darwin wasps.
Structurally, Dolichomitus rather closely resembles Anastelgis Townes and Umanella Gauld in South America. All three genera contain moderately large species with long ovipositors and strong oblique grooves cutting off triangular areas on the anterolateral corners of the second metasomal tergite. Dolichomitus may be easily separated from Anastelgis by the set of the following characters: 1) apex of upper ovipositor valve simple, without tiny denticles (with a row of small denticles in Anastelgis), 2) lower valve of ovipositor laterally expanded to partially enclose the upper valve (lower valve not expanded in Anastelgis) and 3) mid-coxae of males often with prominences which are separated by deep concavities (coxae simple in Anastelgis). Umanella, on the other hand, with only three known species (Gauld 1991, Broad et al. 2010, Herrera-Florez and Molina 2018, is a very distinctive metallic blue pimpline genus which is also characterised by, for example, a very long first metasomal segment. The Central American species of Dolichomitus may be identified with the key provided by Gauld (1991) and Gauld et al. (1998). The South American species may be identified using the key provided by Araujo et al. (2020) and the current article.
The aim of the present study is to describe a striking new species of Dolichomitus from the tropical Ecuadorian Andes. In our opinion, the species is amongst the most spectacular tropical Dolichomitus ever described.

Materials and methods
Morphological terminology follows Broad et al. (2018). The information contained in "Type Material" section corresponds to the specimen label verbatim. The holotype of the new species is deposited in the Museum of Entomology of "Sapienza", University of Rome, Italy (MZUR) and the paratype in Zoological Museum, Biodiversity Unit, University of Turku, Finland (ZMUT). The holotype was collected as part of a larger project carried out by "Sapienza", University of Rome (Italy) on the study of insect biodiversity in Ecuador (collecting permit n° MAE-DNB-CM-2016-0045, export authorisation n° 097-17-EXP-IC-FAU-DNB/MA). High-resolution photographs were taken at different focal stages with a Nikon D5300 digital camera attached to a Leica Z16 APO stereoscope. Images were acquired using StackShoot TM multiple-focus imaging system and stacked in a single infocus image using Zerene Stacker software (version 1.04). Morphological measurements of the species were made with a Leica Z16 APO stereoscope containing a reticle micrometer ruler. Minor corrections at the images were made using the software Adobe Photoshop 2020.  (Fig. 2d); length of CU between 1m-cu&M and 2cu-a about 2.60× as long as 2cu-a. Hind wing with distal abscissa of CU present; length of proximal abscissa of CU about 0.30× as long as cu-a, proximal abscissa of CU vertical, cu-a reclivous and straight. Hind coxa smooth and polished, almost impunctate dorsally and with few small, scattered and setiferous punctures ventrally; hind femur about 5.20× as long as its maximum width.

Dolichomitus meii
Metasoma. Metasoma smooth and shiny, impunctate, only last tergites with barely discernible setiferous punctures (Fig. 2e). ; tergite II about 1.60× as long as posteriorly wide, with strong oblique grooves running from anterior margin to half the tergite, that outline a clearly raised median area; tergite III about 1.10× as long as posteriorly wide, with less defined oblique grooves and a slightly raised median area; tergite IV with small tubercles laterally, near the anterior margin. Ovipositor sheath about 1.10× as long as body and 4.70× as long as hind tibia; ovipositor downcurved posteriorly, ovipositor tip with subapical dorsal lobe of lower valves not delimited posteriorly, but gradually developing into the apical teeth, dorsal lobe with an anterior groove reclivous, followed by three ridges, the first two almost vertical and the third inclivous (Fig. 2f).
Colour. Head, including clypeus and mandible, black, with blue reflections; palps brownish-black with last segment yellowish-brown at the proximal 0.75; antenna, scapus and pedicel black. Mesosoma, including scutellum, postscutellum, tegula and propodeum black with blue reflections. Fore wing yellowish with a distal darkened area that covers the fourth submarginal cell almost entirely; hind wing yellowish; veins and pterostigma orange. All coxae, trochanters and trochantelli black with bluish reflections, inner distal margin of all trochantelli yellowish-brown; fore femur black with bluish reflections, with a yellow line on outer surface running from proximal 0.75 to the apex; mid-femur black with blue reflections, with a yellow spot on outer side at apex; fore and mid-tibiae yellow, fore and mid-tarsi with segments yellow to gradually darker distally, last segment brown; hind femur entirely black with blue reflections, hind tibia and tarsus dull black. Metasoma with tergites I-V orange, tergite II orange with two small black spots on posterior margin just near hind corners, tergites VI+ bluish-black. Ovipositor sheath black.

Diagnosis
Dolichomitus meii sp. nov. can be distinguished from the other Neotropical species of the genus by the combination of the following characteristics: 1) body length ca. 22.0 mm, 2) bluish-black head, mesosoma and metasomal tip, with orange metasomal tergites I-V, 3) wings yellowish with distal darkened area, 4) ovipositor sheath length ca. 4.70× as long as hind tibia and 5) ovipositor tip strongly decurved, with subapical dorsal lobe of lower valves not delimited posteriorly, but gradually developing into the apical teeth, dorsal lobe with an anterior groove reclivous, followed by three ridges, the first two almost vertical and the third inclivous.

Etymology
The specific epithet is in honour of Maurizio Mei, a great entomologist and dear friend of FDG.

Distribution
Ecuador

Biology
Host unknown. Both type specimens have been collected approximately at the same altitude (2000 m a.s.l.).

Taxon discussion
Dolichomitus meii sp. nov. resembles D. orejuelai Araujo & Pádua, 2020 in colour pattern, with body partly dark and metasomal tergites I-V predominantly orange, but it differs from the latter in having mesosoma entirely black with blue reflections (mesosoma mostly reddish-black with red marks in D. orejuelai), metasomal tergite I and III-V entirely orange and metasomal tergite II orange with two small black spots on posterior margin just near hind corners (metasomal tergites yellowish-brown with posterior margins of tergites II-V reddish-black in D. orejuelai) and wings yellowishorange with distal darkened area (wings yellowish, but without distal darkened area in D. orejuelai). In case of the wing colouration, D. meii sp. nov. keys out with D. pimmi Araujo & Pádua, 2020 in the updated key to the South American species of the genus, but it can be distinguished from the latter in having mesosoma entirely black with blue reflections and metasomal tergites I-V orange (mesosoma and metasoma yellow with black marks in D. pimmi).

Male
Unknown.

Identification keys
Updated key to the South American species of Dolichomitus Smith, 1877 (adapted from Araujo et al. 2020) Step 6 of the key, provided by Araujo et al. (2020), should be modified as follows: nov.

Discussion
Almost nothing is known about the biology of tropical American Dolichomitus. The ovipositor tip of D. meii sp. nov. is very strongly decurved; as suggested by Gauld 1991, Dolichomitus species may use their long ovipositors not for actual boring, but rather for threading it down pre-existing tunnels in logs. The shape of the ovipositor tip of D. meii sp. nov. also resembles the ovipositor tip of Umanella. Both genera are known to exist in Western Amazonian rainforests and tropical Andes (Herrera-Florez and Molina 2018, Araujo et al. 2020).
The conspicuous colouration of the species, with head and mesosoma shiny black with blue reflections, golden yellow wings with dark distal area and orange metasoma (with only the last tergites black), is unique. Many large-sized and metallic Darwin wasps are known to occur in South America (mainly Cryptinae and Ichneumoninae). However, within the tropical American species of the subfamily Pimplinae, the metallic blue colouration was previously only known in the genera Pimpla Fabricius and Umanella. To our knowledge, D. meii sp. nov. is the only metallic species of Dolichomitus. In case of D. meii sp. nov., the metallic blue colouration (reflections) of head and mesosoma is clearly visible when observing the specimens under a light source. However, it may be difficult to observe in nature.
With the description of this remarkable species, we hope to draw attention to the largely unknown, yet seemingly diverse, Darwin wasp fauna of the tropical Andes. It is obvious that our understanding of the tropical Andean Darwin wasps is incomplete. Future field studies will likely require us to re-define the current understanding of the diversity patterns of the family.