A new species of Exoristobia (Hymenoptera:Encyrtidae)from China

Guohao Zu·Chen Zhang·Zening Yang·Chengde Li

Abstract Exoristobia sinica sp.nov.is described as new to science and a key is provided to the Chinese species based on females.

Keywords Chalcidoidea·Encyrtinae·Parasitoids·Taxonomy·Tianjin

Introduction

The genusExoristobia,a genus of Hymenoptera parasitic wasps,was established by Ashmead (1904) based on the type speciesE.philippinensisAshmead.Currently this genus consists of nine species (Noyes 2019),one from China(Xu and Lou 2000).The species are distributed throughout the world except for the Neotropics.They are parasites of the Order Diptera,the families Tachinidae,Syrphidae,Anthomyiidae,Calliphoridae,Muscidae,Sarcophagidae,Lepidoptera and Coleoptera,which are possibly reared from Dipteran primary parasitoids such as tachinids (Ashmead 1893;Subba Rao 1970;Noyes and Hayat 1984;Xu and Lou 2000).In this paper,E.sinicasp.nov.is described as new to science.

Materials and methods

The Parasitic wasps were collected from plantations of Chinese red date (Ziziphus jujubaL.) at the Tianjin Agricultural University in a malaise trap,dissected and mounted on slides according to Noyes (1982).Body lengths were measured using a Leica M205A stereomicroscope;other measurements are relative and taken from micrometer divisions placed in the eye piece of a stereozoom microscope for carded specimens,and in the eye piece of a compound microscope for slide-mounted parts,and then transformed into absolute lengths.The Holotype of the new species is deposited in the ’insect collections’ of Tianjin Agricultural University,China.

Morphological terminology and abbreviations is based on Noyes (2010).The following abbreviations are used:F1–6,funicle segments 1–6;AOL,minimum distance between a lateral ocellus and median ocellus;OCL,minimum distance between a lateral ocellus and occipital margin;OD,longest diameter of an ocellus;OOL,minimum distance between a lateral ocellus and the corresponding eye margin;POL,minimum distance between lateral ocelli;OL,length of ovipositor;GL,length of gonostylus or apical segment.

Results

Key to species of Exoristobia (females) from China

1.Clava black,strongly obliquely truncated at apex;antennal toruli with dorsal margins below ventral eye margins······························································E.klinoclavata.

2.Clava yellowish white with basal 1/5 brown,very slightly obliquely truncated;antennal toruli with dorsal margins above ventral eye margins·················································E.sinicasp.nov.

Description of new species

Exoristobia sinicaZuetLi,sp.nov.(Figs.1–14).

HolotypeF#(on slide),CHINA,Tianjin City,Xiqing District,Tianjin Agricultural University,39°5′21′′ N,117°5′38′′E,‒13 m,2018 9.25–10.26,Guohao Zu,Chen Zhang,Zening Yang (TJAU),Malaise trap.

Paratype8F#10 M# (3F#2 M# on slides,5F#8 M# in 99%alcohol at–30 °C),the same data as holotype (TJAU).

DiagnosisFemale (length,excluding ovipositor,1.58–1.99 mm):Body black;scape yellowish brown,clava yellowish white,basal 1/5 brown;wings hyaline;legs dark brown with fore femur in apical half yellowish,mid femur yellowish brown,hind femur with apical 1/4 yellowish,all tibiae yellowish;frontovertex 0.34 × head width;malar space 0.42 × as long as eye height;scape 4.33 × as long as broad;clava as long as F4-6 combined;mid tibial spur shorter than mid basitarsus;ovipositor 1.14 × as long as mid tibia.Male (Figs.8–14) (length,excluding ovipositor,1.29–1.69 mm):Very similar to female except for structure of antenna and genitalia.

Female(Holotype):Body length,excluding ovipositor,1.62 mm.Body generally black,scutellum with blue-green sheen;antenna with scape yellowish brown,funicle segments dark brown,clava yellowish white with about basal 1/5 brown.Wings hyaline;legs dark brown except as follows:fore femur in about distal half yellowish,mid femur yellowish brown,hind femur with apical 1/4 yellowish;all tibiae and tarsi yellowish except last tarsomere dark brown.

Head in front view (Fig.1) 1.13 × as broad as high;frontovertex 0.34 × head width,with obvious piliferous punctures,each about 2 × as long as an eye facet;ocelli forming an angle of 85°;posterior ocellus closer to eye margin than to occipital margin;occipital margin not carinate;antennal toruli with their dorsal margins above ventral eye margins,and separated from mouth margin by about their own height;malar space 0.42 × as long as eye height;mouth about 0.45 × as width as head;frontovertex and face densely setose,setae long and dark brown,the longest setae about 3.5 × as long as an eye facet;eyes densely setose,setae dark brown,and each seta about 2 ×as long as a facet.Antenna (Fig.2) with scape subcylindrical,4.33 × as long as broad and broadest in the middle;F1 slightly longer than broad,all other funicular segments broader than long;linear sensilla present on all funicular segments;clava 1.88 × as long as broad,and about as long as F4-6 combined,sensory area about half of clava length;clypeal margin convexly produced with margin rounded;mandible tridentate,with 2 acute teeth and a broad truncation.Measurements (holotype,μm):head height,460;head width,520;frontovertex width,175;OD,50;POL,69;OOL,11;OCL,24;AOL,44;eye height,330;malar space,138;length and (width)–scape,195 (45);pedicel,80 (50);F1,53 (50);F2,50 (55);F3,48 (58);F4,48 (63);F5,48 (68);F6,43 (73);clava,150 (80).

Fig.1 Exoristobia sinica sp.nov.(female,Holotype):1 head,frontal view;2 antenna;3 thorax;4 fore wing;5 hind wing;6 ovipositor;7 legs.Scale bars=100 μm

Fig.2 Exoristobia sinica sp.nov.(male):8 head,frontal view;9 antenna;10 thorax;11 fore wing;12 hind wing;13 genitalia;14 legs.Scale bars=100 μm

Thorax (Fig.3) with mesoscutum and scutellum with shallow reticulate sculpture but apex of scutellum nearly smooth;scutellum 0.88 × as long as wide.Fore wing(Fig.4) 2.08 × as long as broad;postmarginal vein longer than marginal vein,and nearly as long as stigmal vein;linea calva with anterior 2/3 narrow and setose,posterior 1/3 broad and open.Hind wing (Fig.5) 3.26 × as long as broad.Mid tibial spur gradually tapering,0.3 × as long as mid tibia and shorter than mid basitarsus.Propodeum laterally with a line of setae,posterior margin rounded;spiracles very large,about 1.12 × as broad as anterior ocellus.Measurements(holotype,μm):fore wing length,1275;fore wing width,613;submarginal vein,470;marginal vein,75;postmarginal vein 100;stigmal vein,108;hind wing length,880;hind wing width,270;mid tibia,500;mid tibial spur,150;mid basitarsus,188.Gaster slightly shorter than thorax;ovipositor (Fig.6)exserted,1.14 × as long as mid tibia (Fig.7);hypopygium extending to about 5/6 length of gaster;cercal plates situated in about basal 1/3 of gaster.Measurements (holotype,μm):OL,570;GL,116.

VariationVery little variation in material available.

MaleLength 1.29–1.69 mm.Very similar to female except for structure of antenna (Fig.9) and genitalia (Fig.13).

HostUnknown.

EtymologyThe specific name refers to the new species collected from China.

Comments.The new species is similar toE.nikolskayae(Japan) andE.funeralis(India),but can be separated from them by the yellowish white clava (dark brown innikolskayaeandfuneralis).Furthermore,it differs fromnikolskayaeby its broader fore wing,2.08 × as long as broad(2.25 × innikolskayae),mid tibial spur shorter than mid basitarsus (equal innikolskayae),subcylindrical scape,4.33× as long as broad (about 3 × innikolskayae);fromfuneralisby its shorter ovipositor,1.1 × as long as mid tibia (1.8 × infuneralis),mid tibial spur shorter than mid basitarsus (longer infuneralis).

AcknowledgementsThanks to Dr.John S.Noyes (The Natural History Museum,London,England) for the help of identification of this genus.