A new species of the family Mantispidae (Neuroptera) from Vietnam is described. Euclimacia radioquaesentis sp. nov. shows a unique colour pattern, which is distinctive within the genus. The colouration and morphology of both sexes of the new species are described in detail and illustrated. The naming of the new species is linked to a popular citizen-science event in choosing the name for this species (and three other species from different undescribed species by taxonomists of the Museum für Naturkunde Berlin).

Adaption, lacewings, mimicry, new species, parasitoid, polymorphism, sexual dimorphism, Southeast Asia, wasp mimic

The Mantispidae is a family within the holometabolous order Neuroptera, which has a remarkable morphology and interesting, but so far scarcely studied biology. The larvae of the subfamily Mantispinae are predatory and feeding on spider eggs (Snyman et al. 2020). The larvae of Symphrasinae were observed on various insect pupae and, for Drepanicinae, there is one recorded interaction with a spider (Theridiidae) without further details (Austin 1985). So far, there is only one report on Calomantispinae from a laboratory experiment. Here, larvae were reared on various insect pupae and larvae, as well as on spider eggs and paralysed spiders (MacLeod and Redborg 1982). Mantispidae larvae undergo a hypermetamorphosis with first developmental stage mobile and actively search for food sources (Snyman et al. 2020). An interesting type of behaviour is spider boarding, exhibited by some species of the subfamily Mantispinae. In this case, a larva of the first instar climbs on to a female spider and remains there until she begins to produce her egg sac (Redborg 1998). The larva then intrudes into the egg sac and develops into the second and later third instar. The legs of the third instar are significantly smaller, which restricts locomotion (Snyman et al. 2020).

Adult mantispids are characterised by a triangular head, raptorial forelegs and an elongated tubular prothorax, which makes them appear very similar to mantids (Ardila-Camacho et al. 2021). Adult mantispids are effective ambush predators on other insects. In some species, it is known that they also feed on pollen and nectar (Boyden 1983). Many species show wasp mimicry (Snyman et al. 2018).

Formerly, this family was assumed to be monophyletic, with its extant members classified into four subfamilies: Mantispinae, Calomantispinae, Symphrasinae and Drepanicinae (e.g. Lambkin (1986a, b)). However, recent morphological and molecular studies have convincingly demonstrated that Mantispidae is paraphyletic, with the Symphrasinae being a subfamily in the Rhachiberothidae (Winterton et al. 2018; Ardila-Camacho et al. 2021). The relationships amongst the Calomantispinae, Drepanicinae and Mantispinae, which might be considered as the Mantispidae sensu stricto, are still controversial (see Ardila-Camacho et al. (2023).

Euclimacia Enderlein, 1910 belongs to the most diverse subfamily Mantispinae, which comprises of 320 species in 35 genera (Ohl 2004b; Oswald and Machado 2018). Adult Euclimacia can be easily distinguished from other mantispid genera by the disc-like and symmetrical flagellomeres, the short pronotum (approximately of the same length as the pterothorax), pronounced dorsal humps and lateral maculae and a forked 2A vein in the fore-wing. Species of Euclimacia exhibit a high degree of colour variation. Many mimic different species of aculeate wasps from different families. Colour patterns in Euclimacia vary from almost completely black body colour with blue shimmering wings similar to some Pompilidae to bright yellow and black-striped species, which resemble species of the social wasp family Vespidae (Ohl 2004a; Soh et al. 2022). Currently, there are 33 valid species in this genus, distributed in Oriental and Australasia (Ohl 2004b; Kaur et al. 2021), summarised in Table 1. In 1910, Enderlein initially described Euclimacia, designating E. partita as the type species. The most comprehensive revision of this genus was performed by Handschin in 1961. At that time, only 19 species were known in Euclimacia, but Handschin only included those that were available to him, i.e. a total of 11 species. Of these 11 species, however, he could only personally study the types of four species. In addition, Handschin described six new species.

In the present study, we describe a new species from Vietnam (Fig. 1B), showcasing a unique colour pattern, which distinguishes it from all other described species in Euclimacia.

Figure 1. 

Euclimacia radioquaesentis sp. nov. male holotype and female paratype with distribution map. A. Habitus dorsal holotype male. Insert shows asymmetrical bifurcation between left and right costal area of fore-wings. Antecostal sutures (acs) and glabrous marks (gm) visible. The two black lines on the margin of the wing apex of the right fore-wing indicate the width of the oblique apical dark band; B. Localities (red rhombus) in Vietnam of the radioquaesentis type series. The number in the rhombus symbol indicates the count of specimens in this locality; C. Female paratype radioquaesentis dorsal view. The two black lines on the margin of the wing apex of the right fore-wing indicate the width of the oblique apical dark band. Scale bars: 5 mm (A, B).

The type series is part of the large collection of Southeast Asian Mantispidae deposited in the Royal Belgium Institute of Natural Sciences, Brussels, Belgium. One paratype is housed in the collections of the Museum für Naturkunde, Berlin, Germany.

The genital preparation was made from one paratype. Punctures were made in the area of the fourth abdominal segment with the aid of an insect pin size 0. Polyethylene foam was cut into required pieces, which were attached to the pinned specimen with needles to stabilise it for the preparation. The abdomen was very carefully perforated all around until the posterior part could be detached by a gentle levering action of the needle. The dissected abdominal end was left in 15% potassium hydroxide solution for approx. 21 h, then rinsed with distilled water and transferred to glycerol.

Images were taken with a Sony a7rIII and a Sony Makro G OSS 90mm f 2.8 lens for the habitus and a Canon MP-E 65mm f 2.8 lens for the details. Multi-focus imaging was facilitated by a Novoflex Castel-Mikro stepping motor-controlled focusing rack. To take the images, the software Capture One was used. For stacking, the software Helicon Focus was used. Genital images were made with a Leica Z16 APO A motorised macroscope with a Leica DFC camera. Measurements were done with Fiji (ImageJ) Version 2.1.0/1.53c.

Photos were post-processed with Adobe Photoshop version CC 2019 an arranged and labelled with Adobe InDesign version 19.2.

Illustrations were made with Adobe Illustrator version 25.0.

Distribution map was generated with QGIS version 3.16 Hannover, Natural Earth Data and Adobe Photoshop version CC 2019.

The terminology is based on Snodgrass (1935), Lambkin (1986a), U. Aspöck and H. Aspöck (2008) and Ardila-Camacho (2021).

Euclimacia is a small, but morphologically markedly diverse genus. Despite the considerable size of individual specimens, which can reach sometimes up to 3 cm body length and their striking colouration in many cases, the number of specimens in scientific collections is very limited. So far, there is still no accurate information about their behaviour and their habitats during the day and at night. Euclimacia often represent a by-catch that is caught by scientists specialised in other taxa during light trapping. However, there is no evidence that they are nocturnal. Specific light trapping for Euclimacia has, so far, resulted in low numbers of specimens. It can be assumed that, similar to the genus Climaciella, during the day, they eat pollen and nectar on flowering plants and prey on other insects (Boyden 1983). Presumably they also occur temporarily in higher tree levels.

Of the 33 species described so far, 30 were described on the basis of a single specimen. The remaining two species were described, based on two (Euclimacia superba Lambkin, 1987) and three (Euclimacia nicobarica Kaur, 2021) specimens. The series of eight specimens of the here newly-described species Euclimacia radioquaesentis sp. nov. is thus comparatively large.

Seven males and one female of E. radioquaesentis were examined. The availability of both sexes provides rare data on potential sexual dimorphism in this genus. Only the descriptions of E. superba and E. nicobarica are based on both sexes. In E. nicobarica, the colour pattern of the female is described as similar to the male, although the female is slightly smaller than the male. In E. superba, there are a few differences in the colour pattern and size. The colour differences occur in slightly different colour shades and a few markings. The head of the female is slightly paler and it possesses a transverse band across the antennae basis, which is absent in the male. The female possesses a large dark transverse band on tergite III, the male in the same location possesses a small black median mark. In the female, the ectoproct is black-brown with a brownish-yellow spot. The ectoproct of the male is dark orange-brown without any spot. Wings and other body parts have the same colour. The female is slightly larger than the male. The size depends to a certain extent on the larvae’s food supply (size of the spider egg sac) and is, therefore, considered natural and not as a sexual trait (Lietzenmayer et al. 2022). In addition, Handschin’s re-description of Euclimacia morosa was based on three non-type specimens of both sexes. Handschin described the female and the male as identical in colour (Handschin 1961).

In E. radioquaesentis, there are differences in colouration between females and males. One difference is the transversal band on the prothorax, which is present in both sexes, but reduced in the female. In the males, the pronatal hump is fully covered by a dark mark and this dark mark merges with the dark mark that covers the macula. The pronatal hump of the female has a very faint dark mark at the apex, which does not merge with the dark mark of the macula. In general, the prothorax of the female appears narrower and less wrinkled than of the male (Fig. 3). The pronatal humps are barely developed (Fig. 3B). Whether this is a sexual dimorphism or whether these differences are based on the smaller body size of the female cannot be finally clarified here.

Furthermore, the abdomen of the male is predominantly black with a few brownish markings. The abdomen of the female has a significantly higher amount of brown, so that, apart from the anterior two black segments, the abdomen appears predominantly brown. The predisposition for this brown colouration of the abdomen is also present in the males, as the brown markings on the tergites indicate. The wings also differ, although only slightly, in colouration. The wings of the female appear more contrasting. The area along the posterior wing margin is darker than in the male and the oblique band above 3M in the fore-wing reaches the posterior wing margin. As a result, the hyaline median stripe is enhanced, especially in the fore-wing (Fig. 1C). The most striking feature of the differently-coloured pterostigmata and the adjacent veining is identical.

Intraspecific variation in Euclimacia has also been recorded only occasionally. There are observations of intraspecific variations in Euclimacia badia Okamoto, 1910. Ohl (2004b) examined about 20 specimens from Taiwan, from where the type specimen was collected. The basic colour ranges from reddish-brown to almost black. Within the 20 specimens, there is a morphotype type with a predominantly reddish colour, another morphotype with a predominantly black colour and numerous intermediate stages. Variations within E. radioquaesentis are hardly recognisable. The differences are limited to slight variations in the yellowish shades, which may also be due to the drying process. Colouration can deviate from that of the living specimen due to the drying and ageing process. From observations of other specimens of Euclimacia of which the appearance in the dried and living state is known, it can be said that black colour patterns fade to dark brownish and yellow colouring appears less intense in the dried state, but rather goes into ochre or sand colour.

Furthermore, the individuals differ slightly in size. Variation also occurs in the wing venation. There are variations between specimens, but also asymmetry within the same specimen. The asymmetry of subcostal veinlets within the wings of one specimen seems to be the norm.

Intraspecific variability within this genus is still difficult to assess and, in an ongoing revision, as much material as possible from this genus will be investigated. The trend indicates that there are species with hardly any intraspecific variability, as in the example of radioquaesentis and species with clear intraspecific variability, as in badia. Adaptation to morphologically different mimicry models (i.e. aculeate wasps) in different regions may result in intraspecific variability.

The description of E. radioquaesentis was linked to a popular science event of the Museum für Naturkunde Berlin and ‘Inforadio vom rbb’, one of Berlin’s local radio stations, in choosing the name for this species. Three more species from different taxa were also involved, the descriptions of two of which have already been published (a species of shrimp by Klotz et al. (2023); a staphylinid species by Frisch and Mainda (2022)). A species profile was broadcast by ‘Inforadio’ and listeners were asked to propose a scientific name (the species epithet). Amongst the suggestions submitted, the species name E. radioquaesentis was picked as being most suitable for species named by radio listeners. The goal of this radio event was to raise awareness of the high number of still undescribed species and to let interested citizens participate in taxonomic projects.

We thank the collectors of the specimens relevant to this species description in Huong Hoa Nature Reserve Vietnam (1 holotype, 4 paratypes): Truoung Sor. Nguyen, Duc Tien Pham, Thien Tao Nguyen, Xuan Nghia Nguyen and Gábor Csorba.

We thank the collectors of the sixth paratype in Kon Chu Rang Nature Reserve Vietnam: Jerome Constant, Joachim Bresseel and Xavier Vermeersch.

We thank the collectors of the seventh female paratype in Cuc Phuong National Park Vietnam: Jerome Constant and Pol Limbourg.

We gratefully acknowledge the Royal Belgium Institute of Natural Sciences, Brussels, Belgium for the loan of the specimens.