Eusemion Dahlbom 1857
Creators: name: Noyes, John Stuart
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Hymenoptera
Encyrtidae
Eusemion

description: Genus EUSEMION Dahlbom   
 Eusemion Dahlbom 1857:293. Type species: Encyrtus corniger Walker, by subsequent monotypy (Thomson, 1876:154).   
Female. Length about 0.9-2.0mm.  
Body orange-brown to dark brown and metallic; mesoscutum and scutellum usually dark blue or purple; head variously dark metallic blue, purple, and green; forewing (Figs 1253, 1255) infuscate with apex hyaline, apices of postmarginal vein and stigmal vein connected by a naked, hyaline streak or sometimes only a paler streak.  
Head with setigerous punctures on frontovertex shallow and inconspicuous or well-defined and about the diameter of an ocellus; facial depression delimited dorsally by a curved, non-carinate, sometimes weak, frontofacial ridge (Fig. 1260); antennal scrobes semicircular, sharply margined by a carina dorsally; torulus about equidistant from mouth margin and lower margin of eye; scape very broad and flattened, subtrapezoidal in shape; pedicel subtriangular in profile at least about as wide as F1, dorsally convexly rounded; funicle segments, very transverse, relatively broad and slightly flattened, hence very broadly oval in cross-section; club 3-segmented, a little longer than funicle, sensory area extending about half way along ventral surface forming an oblique apical truncation; malar suture absent; mandible tridentate, the upper tooth apically less acute than the 2 ventral teeth; palp formula 4-3.  
Fore wing with parastigma at least slightly swollen, sometimes distinctly expanded and triangular, marginal vein about 4X as long as broad, about 2X as long as stigmal vein and 3X as long as postmarginal vein; filum spinosum present; composed of about 2-4 modified setae; thorax in profile with propodeum narrowly in contact with hind coxa, dorsally with mesoscutum and scutellum quite flat; mesoscutum without notaular lines; mesopleuron not quite reaching level with posterior margin of propodeum, falling short by about diameter of propodeal spiracle.  
Gaster a little longer than thorax; syntergum about as long as middle tibia; hypopygium reaching about halfway along gaster, slightly more than 2X as wide as long; paratergites absent; ovipositor hardly exserted; gonostylus free.  
Male. Length about 1mm.  
Generally very similar to female apart from structure of head, antenna and genitalia; fore wing infuscate as in female and with similar setation; head about 2X as wide as frontovertex; sculpture of frontovertex rather coarse polygonally reticulate; piliferous punctures relatively few, shallow and indistinct; scape hardly broadened, about 3X as long as broad; funicle segments subcylindrical, each at least 2X as long as broad, clothed with whorls of long setae, the longest of which is about 3X as long as diameter of segment; clava entire, slightly shorter than F5-F6 combined.  
DISTRIBUTION. Holarctic, central America.  
 HOSTS. Secondary parasitoids of various scale insects, mainly soft scales (Hemiptera: Coccidae), but also mealybugs, kermesids, eriococcids and armoured scales (Hemiptera: Pseudococcidae, Kermesidae, Eriococcidae, Diaspididae) via encyrtid (Hymenoptera: Encyrtidae) primary parasitoids (e.g. Blastothrix Mayr, Trichomasthus Thomson, Metaphycus Mercet) (see Peck, 1963; Trjapitzin, 1989).   
 COMMENTS. The diagnostic features of Eusemion have been expanded a little to accommodate Eusemion monos sp.nov. which may be a little out of place in the genus. This species has a very distinct triangular expansion of the parastigma and lacks deep setigerous punctures on the frontovertex and the proximal funicle segments are much less transverse than in cornigerum, longipennis and themisto. The three other named species certainly belong to Eusemion but lack a triangular expansion of the parastigma and have deep, distinct setigerous punctures on the frontovertex. At this time, these differences are probably not enough to warrant separate generic status without a full phylogenetic analysis of the group.   
 IDENTIFICATION. Previously, only two species known which may be synonymous: Eusemion cornigerum (Walker, 1838) (see Annecke, 1967; Trjapitzin, 1989) from the Palaearctic and Eusemion longipennis (Ashmead, 1888) (see Peck, 1963) from the Nearctic.
description: Published as part of Noyes, John Stuart, 2023, ENCYRTIDAE OF COSTA RICA (HYMENOPTERA: CHALCIDOIDEA), 4 Subfamily Encyrtinae: tribes Arrhenophagini, Habrolepidini, Cerapterocerini, Cheiloneurini, Trechnitini, Cercobelini, Polaszekiini, Protyndarichoidini, Gahaniellini and Syrphophagini (part), mainly primary parasitoids and hyperparasitoids of Coccoidea and Psylloidea (Hemiptera), pp. 1-921 in Taxonomic Monographs on Neotropical Hymenoptera (Oxford, England) (Oxford, England) 2 (11) on pages 499-500, DOI: 10.5281/zenodo.8074943