Meteorus stellatus Fujie, Shimizu & Maeto, 2021

Fujie, Shunpei, Shimizu, So, Tone, Koichi, Matsuo, Kazunori & Maeto, Kaoru, 2021, Stars in subtropical Japan: a new gregarious Meteorus species (Hymenoptera, Braconidae, Euphorinae) constructs enigmatic star-shaped pendulous communal cocoons, Journal of Hymenoptera Research 86, pp. 19-45 : 19

publication ID	https://dx.doi.org/10.3897/jhr.86.71225
publication LSID	lsid:zoobank.org:pub:4C11898D-A5A4-44BD-89C2-D049E6B991B4
persistent identifier	https://treatment.plazi.org/id/D8785F79-E874-4854-95D7-5C0A928914CA
taxon LSID	lsid:zoobank.org:act:D8785F79-E874-4854-95D7-5C0A928914CA
treatment provided by	Journal of Hymenoptera Research by Pensoft
scientific name	Meteorus stellatus Fujie, Shimizu & Maeto
status	sp. nov.

Treatment

Meteorus stellatus Fujie, Shimizu & Maeto sp. nov.

[Japanese name: Hoshigata-haraboso-komayubachi] Figs 2 View Figure 2 , 3 View Figure 3

Etymology.

The specific name is a masculine Latin word, " Meteorus stellatus ", meaning “starry”, which is derived from the unique shape of the cocoon masses.

Type series.

41♀♀ 40♂♂ (all from Japan). Holotype ♀ (OMNH): "Japan: Okinawa Is., Okinawa City, Goya / Kitanakagusuku Vil., Shimabukuro, Okinawa Kodomono-kuni, 3. VI. 2019 cocoon masses), K. TONE et al. leg." "9. VI. 2019 emerged".

Paratypes: 1♀2♂♂ (OMM), same as holotype; 2♀♀2♂♂ (OMM), Okinawa-kodomonokuni, Goya, Okinawa City /Shimabukuro, Kitanakagusuku Vil, Okinawa-hontô Is., collected as cocoon masses on 13.V.2019 and emerged on 19.V.2019, Koichi Tone et. al leg.; 2♀♀2♂♂ (OMNH), Nago City, Okinawa-hontô Is., collected as cocoon masses on Morinda umbellata and emerged on 23-24.V.2011, Masashi Sugimoto leg.; 4♀♀4♂♂ (OMNH), Nago City, Okinawa-hontô Is., collected as host larva of Macroglossum passalus passalus , and adult wasps emerged on XII.2010 (2♀♀2♂♂) and I.2011 (2♀♀2♂♂), Masashi Sugimoto leg.; 2♀♀2♂♂ (RUM), Hentona, Kunigami Vil., Okinawa-hontô Is., collected as cocoon masses on 14.IV.2011 and emerged on 19.IV.2011, Koichi Sugino leg.; 2♀♀2♂♂ (ZISP), Hentona, Kunigami Vil., Okinawa-hontô Is., collected as cocoon masses on 30.X.2010 and emerged on 7.XI.2010, Kozue Miyagi leg.; 2♀♀2♂♂ (NARO), Aha, Kunigami Vil., Okinawa-hontô Is., collected as cocoon masses on 23.X.2010 and emerged on 25.X.2010, Yasuji Kakazu leg.; 2♀♀2♂♂ (OMNH), Okinawa-kodomonokuni, Goya, Okinawa City, Okinawa-hontô Is., collected as host larva of Macroglossum pyrrhosticta feeding Paederia scandens on 3.VI.2019, cocoon masses formed on 9.VI.2019, and emerged on 17.VI.2019, Yu Erh Chen leg.; 2♀♀2♂♂ (CNC), Ryukyu University, Nishihara Town, Okinawa-hontô Is., collected as cocoon masses on 22.VI.2005 and emerged on 25-29.VI.2005, Kazuo Minato leg.; 20♀♀20♂♂ (ELKU, EMUS, EUM, KPMNH, MNHA, NHMUK, NSMT, OMM, SEHU and TARI with 2♀♀2♂♂ each), Yoshihara, Chatan Town, Okinawa-hontô Is., collected as cocoon masses on 4.VI.2020 and emerged on 9-11.VI.2020, Tamami Gushiken leg.; 1♀ (OMNH), Chuo-rindo, Amami City, Amami-ôshima Is., 5.VII.2013, Shunpei Fujie leg.

Non-types.

323♀♀228♂♂ adults; 29 cocoon masses (see Suppl. material 1: Table S1).

Distribution.

Japan (Ryukyus: Okinawa-hontô Island and Amami-ôshima Island).

Differential diagnosis.

Meteorus stellatus sp. nov. is most similar to M. komensis (Fig. 4 View Figure 4 ) but can be distinguished from the latter by the following combination of characters: the comparatively larger posterior ocelli (in M. stellatus sp. nov., OOL/OD = 1.2-1.6, while 1.7 in M. komensis (Fig. 4C View Figure 4 )), the medially longitudinally strigose first metasomal tergite (Figs 2J View Figure 2 , 3F View Figure 3 ) (fairly striate in M. komensis , as is shown in Fig. 4E, F View Figure 4 ). Meteorus stellatus sp. nov. is also very similar to M. kurokoi but can be distinguished from M. kurokoi by the face width (1.5-1.8 × its height in M. stellatus sp. nov. (Figs 2E View Figure 2 , 3B View Figure 3 ), while 1.2-1.3 × in M. kurokoi ) and the sculpture of frons (frons with a median longitudinal or a pair of carinae in M. stellatus sp. nov. (Fig. 2G View Figure 2 ), but smooth without any carinae in M. kurokoi ).

In the key to species of Meteorus from the West Palaearctic region ( Stigenberg and Ronquist 2011) and China ( Chen et al. 2004), M. stellatus sp. nov. would run to M. versicolor (Wesmael), but can be distinguished from M. versicolor by the face width (1.5-1.8 × its height in M. stellatus sp. nov. (Figs 2E View Figure 2 , 3B View Figure 3 ), while 1.0-1.2 × in M. versicolor ), the sculpture of frons (with a median longitudinal or a pair of carinae in M. stellatus sp. nov. (Fig. 2G View Figure 2 ), but smooth in M. versicolor ), and the shape of temple (Figs 2C View Figure 2 , 3C View Figure 3 ) (roundly narrowed in M. stellatus sp. nov. (Figs 2C View Figure 2 , 3C View Figure 3 ), but directly narrowed in M. versicolor ).

The results of a GenBank BLAST search showed that the CO1 sequences of M. stellatus sp. nov. were closest to those of M. arizonensis Muesebeck and M. tarius Huddleston. However, M. stellatus sp. nov. can be distinguished from M. arizonensis by its smaller body (the body lengths of M. stellatus sp. nov. and M. arizonensis are 2.9-3.9 mm and 4.6-5.5 mm, respectively), the longer malar space (the malar space length 1.0-1.4 × the basal mandibular width in M. stellatus sp. nov. whereas 0.6-0.7 × in M. arizonensis ), the shorter ovipositor sheaths (the ovipositor sheath length 1.1-1.2 × length of the first tergite in M. stellatus sp. nov. and 1.6-1.9 × in M. arizonensis ); the species can be distinguished from M. tarius by its broader face (the face width 1.5-1.7 × its height in M. stellatus sp. nov. whereas approximately 1.0 × in M. tarius ) and the position of the forewing vein m-cu (slightly antefurcal to interstitial in M. stellatus sp. nov., but far antefurcal in M. tarius ).

Description.

Female (holotype; Fig. 2 View Figure 2 ). Body length 3.6 mm.

Head (Fig. 2B, C, F, H, I View Figure 2 ). Width of head 1.7 × median height. Length of eye 1.7 × length of temple in dorsal view. Temple roundly narrowed posteriorly. Eyes large and moderately convergent ventrally. Face with width 1.6 × height; distinctly and densely transversely striate with fine granulation. Clypeus as wide as face, distinctly separated from face, and punctate-rugose. OOL / OD = 1.2. POL / OD = 1.4. Frons widely smooth, anteriorly with a pair of obscure carinae. Vertex and temple almost smooth. Length of malar space 1.1 × basal mandibular width. Antennae with 26 segments; 4th segment 3.1 × longer than wide; and penultimate one 1.9 × longer than wide.

Mesosoma (Fig. 2D, E, J View Figure 2 ). Mesosoma length 1.4 × height. Mesoscutum entirely covered with short and dense pale setae; median lobe weakly punctulate in anterior 0.6 and mostly rugose reticulate in posterior 0.4; lateral lobes weakly punctulate. Notauli shallow, wide, complete, coarsely rugose-reticulate. Prescutellar depression deep, almost straight, with often five rather fine carinae. Scutellum smooth and distinctly convex. Mesopleuron mostly punctulate, and rugose reticulate anterodorsally. Precoxal sulcus shallow and widely rugose-reticulate. Propodeum entirely coarsely rugose reticulate without median longitudinal carina.

Wings (Fig. 2G View Figure 2 ). Fore wing with 3.1 mm in length, length of pterostigma 2.9 × maximum width, 3-SR / r = 1.2, m-cu distinctly (left) to slightly (right) postfurcal, cu-a far postfurcal, 1-CU1 / cu-a = 0.8. Hind wing with 1M / cu-a = 0.8, 1M / 1r-m = 0.6.

Legs. Tarsal claws with a distinct submedial lobe. Hind leg: outer surface of coxa punctate; femur 4.7 × longer than wide, and distinctly and densely punctate.

Metasoma (Fig. 2J, K, L View Figure 2 ). 1st tergite 1.6 × longer than apical width; dorsopes absent; mostly smooth anteriorly, longitudinally strigose with some rugosity medially, densely striate in posterior 0.3; ventral borders jointed from the base of segment to about middle point. Remaining terga smooth. Ovipositor slightly down-curved; length of ovipositor sheath 0.7 × C+SC+R, 0.3 × fore wing, and 1.2 × 1st tergite.

Color (Fig. 2A View Figure 2 ). Brownish yellow, except for following parts infuscate: stemmaticum, apical segments of antennae, dorsal part of propleuron, side of scutellum, metanotum, propodeum, apex of hind femur and tibia, posterior half of 1st tergite, 2nd tergite (often except for anteromedially), 3rd tergite and ovipositor sheath; and palpi pale yellow. Wing membrane hyaline; pterostigma light brown, faintly paler basally.

Variation. Body length 2.9-3.9 mm. Width of head 1.6-1.8 × median height. Length of eye 1.5-1.7 × length of temple in dorsal view. Face with width 1.5-1.7 × height. OOL / OD = 1.2-1.6. POL / OD = 1.3-1.7. Frons with a longitudinal carina or a pair of obscure carinae. Length of malar space 1.0-1.4 × basal mandibular width. Antennae with 26-31 segments; 4th segment 2.9-3.6 × longer than wide; and penultimate one 1.7-2.0 × longer than wide. Mesosoma length 1.4-1.5 × height. Fore wing length 2.7-3.5 mm with length of pterostigma 2.8-3.3 × maximum width, 3-SR / r = 0.8-1.4, m-cu distinctly postfurcal to interstitial, 1-CU1 / cu-a = 0.6-1.1. Hind wing with 1M / cu-a = 0.6-1.0, 1M / 1r-m = 0.5-0.7. Hind femur 4.6-4.9 × longer than wide. 1st metasomal tergite 1.5-1.8 × longer than apical width; longitudinally strigose with often some rugosity medially; length of ovipositor sheath 0.6-0.8 × C+SC+R and 1.1-1.2 × 1st tergite. 2nd tergite brownish yellow to infuscate anteromedially. Pterostigma unicolored or faintly paler basally.

Males (Fig. 3 View Figure 3 ). Similar to females, except for length of eye 1.6-1.9 × length of temple in dorsal view; width of face 1.6-1.8 × height; OOL / OD = 1.1-1.4; POL / OD = 1.4-1.8; length of malar space 1.1-1.7 × basal mandibular width; antennae with 27-31 segments; penultimate segments of antenna 2.2-2.8 × longer than wide; hind femur 4.6-5.1 × longer than wide; 1st metasomal tergite 1.6-1.9 × long than apical width; propleuron not darkened dorsally.

Hosts and host plants.

Two species of Sphingidae ( Lepidoptera ) were identified as hosts of M. stellatus sp. nov.: Macroglossum passalus (Drury) feeding on Daphniphyllum glaucescens Blume ( Daphniphyllaceae ) and M. pyrrhosticta Butler feeding on Paederia foetida Linnaeus [= P. scandens (Lour.) Merr.] ( Rubiaceae ). All wasp larvae of M. stellatus sp. nov. emerged from mature larvae of the host sphingids.

Hyper-parasitoids.

Some hymenopteran hyper-parasitoids emerged from the cocoon masses after the emergence of M. stellatus sp. nov. adults. The following three species were identified as morphospecies at the generic level: Tetrastichus sp. ( Eulophidae ), Eurytoma sp. ( Eurytomidae ), and Aphanogmus sp. ( Ceraphronidae ) (Suppl. material 2: Table S2).

Habitats.

Despite the multiple field collection sessions at primary forest areas in the Okinawa-hontô and Amami-ôshima Islands, only one specimen of M. stellatus sp. nov. was sampled from a secondary evergreen forest in the latter island. Most other specimens of M. stellatus sp. nov. were collected from a campus of the University of the Ryukyus, urban parks, and back yards in Okinawa-hontô Island, by finding suspended cocoon masses or rearing host larvae. As the host sphingids and their host plants are abundant in or around the edges of sparse forests, M. stellatus sp. nov. likely prefers rather open forests.

Phenology.

The emergence of adult wasps occurred from April to June and from October to January, but not during the hottest season from July to September (Fig. 5 View Figure 5 ).

Secondary sex ratio.

The proportion of males (secondary sex ratio) ranged from 0.20 to 0.64, showing a gradual increase with the total number of wasps per host larva (Fig. 6 View Figure 6 ). The positive effect of the total number of wasps on the sexual ratio was significant (B = 0.010, Wald Chi-Square = 18.129, df = 1, p <0.001). The estimated mean of the proportion of males was 0.36 (95% confidence interval = 0.31-0.42, significantly less than 0.50) in the average number of total wasps (50.5), indicating an overall female-biased sex ratio.

Cocoon mass formation.

The third author observed a case of larval emergence and subsequent cocoon formation in the laboratory. At approximately 1:30 p.m. on June 9, 2019, approximately 100 larvae of M. stellatus sp. nov. emerged from the abdomen of a matured larva of M. pyrrhosticta on the vine of P. foetida by chewing holes (Fig. 7A View Figure 7 ). The larvae commenced hanging down from the host plant substance with their own suspensory threads as soon as they emerged (Fig. 7B View Figure 7 ). The larvae began to cluster by actively rotating, twisting, swaying, and horizontally stretching (Fig. 7C View Figure 7 ). When the larvae found the threads of other individuals, they actively went down, intertwined with said threads, and eventually merged together. Once they formed a large mass, the mass did not descend any more (Fig. 7D View Figure 7 ). In rare cases, several larvae moved from the upper mass to the lower mass as the cable of the former intertwined with that of the latter, owing to the blowing wind. No further larval transfer was observed after approximately 70 min of the emergence of the larvae. Initially, the shape of the larval masses was irregular (Fig. 7E View Figure 7 ), but gradually the larvae adopted a spherical shape (Fig. 7F, G View Figure 7 ). The larvae twisted their upper bodies and spun the thread at the posterior of their body, namely inside the cocoon mass. The silk walling action lasted approximately 40 min, along with the spinning of their own individual cocoons (Fig. 7H, I View Figure 7 ). Finally, three cocoon masses were completed approximately 2 h after larval emergence (Fig. 7J View Figure 7 ). A video of the entire process of cocoon mass formation is available at the following address: https://www.youtube.com/watch?v=AuHarLHolPM.

The host sphingid died on the following day after wondering. The color of the cocoons gradually darkened over a few days. After 8 days, 68 females and 23 males of M. stellatus sp. nov. emerged from these three cocoon masses. The wasps emerged simultaneously, cutting the tip of each cocoon.

Characteristics of the cocoon masses.

The cocoon masses of M. stellatus sp. nov. (Fig. 8 View Figure 8 ) were light brown to brown, 7-14 mm in width, 9-23 mm in length, and regularly spherical to ovoid with minimally 12 (Fig. 8D View Figure 8 ) to maximally over 100 cocoons (Fig. 8C View Figure 8 ). Exceptionally, approximately 200 cocoons formed a collapsed large mass in an artificial breeding case (Fig. 8B View Figure 8 ). Each cocoon mass was suspended by a single thick cable. The cable was 12-100 cm in length. Although most larvae constructed such cocoon masses, sometimes a few single larvae formed their own cocoons on the cable (Fig. 8F View Figure 8 ). The cable consisted of individual threads, which were tightly intertwined, like a rope (Fig. 8G View Figure 8 ). The anterior third to half of individual cocoons was exposed outward and fairly distributed on the spherical or ovoid surface. The posterior half of individual cocoons was invisible under the dense silk wall. Adults emerged by opening an anterior outside cocoon cap, which was circular shaped and tapering (Fig. 8F View Figure 8 ). Cocoons with such a regular cap are typical of the Meteorus pulchricornis clade of Meteorus ( Askari et al. 1977; Maeto 1989a, b, 1990a).

Phylogeny of Meteorini and affinity of M. stellatus sp. nov.

The Meteorini phylogeny is illustrated in Fig. 9 View Figure 9 . The Meteorini classification was also revised based on our phylogeny and those of Maeto (1990b) and Stigenberg et al. (2011) (Table 3 View Table 3 ). Although our topology was poorly resolved at the species level, it was mostly congruent with that of Stigenberg and Ronquist (2011). Meteorini was recovered as a monophyletic group. Meteorini species were divided into five clades (Fig. 9 View Figure 9 ; Table 3 View Table 3 ). Zele was recovered as a robustly supported monophyletic clade and nested within Meteorus species. Monophyly was robustly supported for the Meteorus ictericus and Meteorus pulchricornis clades but not for the unresolved clade. The Meteorus pulchricornis clade was divided into four internal subclades (the Meteorus colon , Meteorus pendulus , Meteorus pulchricornis , and Meteorus rubens subclades).