﻿A new genus and three newly recorded species of Encyrtidae (Hymenoptera, Chalcidoidea) from China

﻿Abstract A new genus and species of Encyrtidae (Hymenoptera: Chalcidoidea), Apteronotus Kang, Hu & Luo, gen. nov. (type species A.indigus Kang, Hu & Luo, sp. nov.), associated with insects inhabiting Oxytropis spp., and three newly recorded species for China, Copidosomaclavatum, Ericydnusaeneus and Tetracnemuskozlovi, are described from the Altun Mountain Nature Reserve, Xinjiang. Detailed illustrations of all species were included to support the identification and further study.


Introduction
Encyrtidae, a large family in Chalcidoidea (Hymenoptera), is characterized by their extensive diversity and cosmopolitan distribution, encompassing over 500 genera and 4700 species worldwide, among them, 128 genera and 483 species recorded from China.Encyrtidae are predominantly parasitoids, targeting a wide range of host taxa primarily within Hemiptera, but also extending to Lepidoptera, Coleoptera, Diptera, and other insect groups, as well as other arthropods, including ticks (Noyes 2019).The majority of Encyrtidae species are endoparasitoids, and a few of them are hyperparasitoids (Trjapitzin 1989).Many species of this family have been utilized in the biological control of crop pests, underscoring the family's ecological and biogeographical significance.
A critical milestone in the study of Chinese Encyrtidae was achieved by Zhang and Huang (2004), who provided an extensive key to 123 genera.Despite this, knowledge of the biological resources of Encyrtidae in vast areas of China is still limited.The Altun Mountain National Nature Reserve, located in Xinjiang, China, is one of China's four uninhabited areas, which is characterized by unique extreme environmental conditions such as low temperature, strong winds, and high ultraviolet radiation, as well as complex and diverse habitats like widespread sandy and gravel deserts, wetlands and alpine steppes.Under such environmental conditions, the poorly known species of Encyrtidae need to be investigated comprehensively and urgently to reveal its biodiversity and enrich available data on the family for further study on its adaptation to the extreme environment.
In this context, our study focused on encyrtids collected from 2019 to 2021 in the dominant alpine steppes' habitats within the Altun Mountain Nature Reserve.This research contributes to the taxonomic understanding of the family by documenting four species across four genera.Notably, it includes one new genus, Apteronotus Kang, Hu & Luo, gen. nov., and one new species, Apteronotus indigus Kang, Hu & Luo, sp. nov.Additionally, we report three species, Copidosoma clavatum, Ericydnus aeneus and Tetracnemus kozlovi, as new distributional records for China.This work represents a significant step in unraveling the taxonomic and ecological complexities of Encyrtidae in an alpine region that has been historically underrepresented in entomological research.

Materials and methods
All the examined specimens were collected by using sweeping nets, yellow pan traps as well as malaise traps in July from 2019 to 2021; yellow pans were left from 8 to 24 hours at each site, and alcohol in the malaise traps was changed every 10 (±5) days to 1 month.The specimens were sorted and immediately preserved in absolute ethanol and stored at -20 °C.Selected specimens of both sexes were slide-mounted and labeled or air-dried and card mounted, and examined under a Nikon SMZ745T stereomicroscope using the available keys (Trjapitzin 1989;Zhang and Huang 2004).Habitus photographs were taken with a Nikon D7000 digital camera connected to a Nikon SMZ25 stereomicroscope.Detailed features of the new species were photographed with a LEO-1430VP scanning electron microscope (SEM), and plates were compiled using Adobe Illustrator CC 2017 software.All specimens were deposited in the Insect Collection of the College of Life Science and Technology, Xinjiang University, Urumqi, Xinjiang, China (ICXU).
The taxonomic terminology and abbreviations follow Trjapitzin (1989).The following abbreviations are used in the text: F1-6, funicle segment number; POL, distance between the posterior ocelli; OOL, distance between the eye margin and the adjacent posterior ocellus; OCL, distance between the posterior ocellus and the occipital margin; and T1-7, tergite segment number.Etymology.Female, "Apteron" refers to lack of wings in this genus, and "notus" is a suffix often used in insect taxonomy.

Genus
Diagnosis.This genus exhibits distinct morphological divergences when compared to the two subfamilies (Encyrtinae and Tetracneminae) in Encyrtidae.The new genus can be differentiated from other related genera by a combination of the following characteristics: Body length 0.65-0.75mm, short and robust, body indigo blue, eyes and ocelli dark red, mandible yellow, tibia and trochanter yellow, basitarsus, and apical tibiae yellow.Head in dorsal view without occipital margin; antenna slender, slightly longer than head width, clava 3-segmented; mesoscutum slightly shorter than head width, with faint reticulation and sparse setose; notaular lines absent, axillae separate apically; propodeum shorter than 1/2 scutellum medially; wings absent in both sexes; mid tibial spur shorter than basitarsus; gaster ovate, posterior margin of T1 medially incised in some individuals, ovipositor sheath not exserted, paratergite not present.
Comments.The genus does not run to any genus in the keys (Trjapitzin 1989;Noyes et al. 1997).Extensive morphological comparisons were made with several brachypterous genera (Trjapitzin and Gordh 1979); however, Globulencyrtus Hoffer, 1976 differs in the following characteristics: head with sharp occipital margin, clava shorter than funicle, forewing rudiments, and reaching to about apex of scutellum posteriorly (Hayat et al. 2013); Austrochoreia Girault, 1929 is distinguished by the elongate pronotum that almost covers the mesoscutum, lack of notaular lines and abbreviated wings (Noyes and Hayat 1984); it can be distinguished from Aglyptus (Tetracneminae) by several key characteristics: body chocolate-brown-yellow, with light green shine, female body length 1.9-2.0mm, forewing not developed and with dark transverse band in the apical third; similarly, the related genus Bactritopus with large and deep depression on face, clypeal margin forming a spatulate protrusion, antennal toruli located at the edge of mouth, mandible tridentate, with a long middle tooth, mesoscutum with complete notauli, wings not shortened (Trjapitzin 1978).The specimens also share some characteristics with the genus Choreia (Encyrtinae), but they differ notably in having a large punctation on the vertex and frons, occipital margin sharp, mesoscutum usually 3× as broad as long, scutellum roundish in back view, axillae meeting, and female body length at least 1 mm (Westwood 1833;Förster 1856).We also found some characteristic differences within the new species, the hind margin of T1 slightly incised medially in some individuals.Description.Female.Length 0.7 mm.Body black with dark bluish metallic sheen (Fig. 1A).Antenna, femora, and tibiae dark brown, head in dorsal view with bronze shine at some angle.Mesosoma black.Legs with all coxae black; trochanter and their apices deep yellow, tarsal segments 1-3 yellow, fourth and fifth tarsi dark brown (Fig. 2C).Gaster black except T6-7 dark brown.
Gaster 1.6× as long as broad (694:426), longer than the combined length of head and mesosoma, T1 distinctly longer than other tergites individually (250:444), occupying about two-fifths of the total length, covered with 3-4 rows of setae, T2-T6 each with a single row of setae, T7 with 2-3 rows of short setae, and with 5 long cercal bristles at each side.Paratergites absent.Hypopygium slightly extends to the apex of gaster (Fig. 1G, H).
Hosts.Unknown.Etymology."indigus" means indigo blue, signifying the body color of the female species.
Comments.The similar species C. aretas can be separated from this species by the body color dark green, funicle elongated distally, scape more than 6× as long as width, clava without oblique truncation, and forewing linea calva interrupted posteriorly (Trjapitzin 1989).
Comments.Ericydnus danatensis is similar to E. aeneus but differs in the following characters: head 1.5× as wide as long, torulus at the level of lower eye margin, forewing with distinct dark bands (Myartseva 1980;Sharkov 1986).

Genus Tetracnemus Westwood, 1837
Note.The most important characteristics of the genus are the wide and flat flagellum, clava only one segment, and mandible bidentate.The genus encompasses 36 species worldwide, with three species recorded in China.These species are widely distributed throughout the world and their dominant hosts belong to Pseudococcidae (Noyes 2019).Diagnosis.Female.Length 1.5-2 mm, body deep green with purple metallic luster at mesoscutum (Fig. 5A); eyes dark red, mandible yellowish-brown; antenna and legs dark brown, scape with metallic reflection; wings with basal 2/3 hyaline and tip 1/3 with dark band; the distal 1/2 of tibiae and tarsi yellow.Torulus below the ventral edge of eyes (Fig. 5B); scape distinctly enlarged ventrally, flagellum obviously widened (Fig. 5C), ocelli forming an acute angle (75-85°), OCL 2.15× OOL; scape about 2× as long as broad, and ventral side enlarged obviously, all the funicles transverse, clava unsegmented.Mesoscutum with shallow reticulate engraving, axillae separated medially, wings degenerated, not exceeding the propodeum and truncated distally (Fig. 5D).The exserted part of ovipositor 0.6× gaster length.
Comments.For the similar short-winged species within the genus, there are obvious morphological differences compared to this species.For example, the antennal scape of T. subapterus is not broadened or flattened, each funicle segment is longer than wide, and the ovipositor sheaths are very short.The base of the antennal scape in T. hofferi is noticeably shortened, ovipositor sheaths are about 2/3 length of gaster, and the head has a deep microcellular sculpture.The antennal scape of T. heydeni is smoothly rounded ventrally, ocelli form an equilateral triangle, and the outer edges of the scrobes are acute (Trjapitzin 2012).

Figure 3 .
Figure 3. Copidosoma clavatum Myartseva, female A habitus, lateral view B head and mesoscutum, dorsal view C forewing D antenna E fore leg F mid leg G hind leg.Scale bars: 100 μm.