Plagiomerus, Timberlake

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), Taxonomic Monographs on Neotropical Hymenoptera (Oxford, England) 2 (11), pp. 1-921 : 41-42

Genus PLAGIOMERUS Timberlake

Plagiomerus Crawford, 1910:89 . Type species: Plagiomerus diaspidis Crawford , by monotypy. Parahomalopoda Girault, 1915b:170 . Type species: Parahomalopoda peruviensis Girault , by

monotypy. Synonymy with Plagiomerus by Noyes (1980:222).

Female. Length about 0.6-1.5mm.

Body generally dark with a metallic sheen; palpi white; scutellum coppery purple with some blue; legs dark brown with white, pale yellow and pale orange areas, tibiae with distinct dark brown, subbasal rings; wings hyaline.

Head in facial view about 3.0-5.3X as wide as frontovertex, in profile about 1.5-1.6X as high as deep, triangular with frontovertex moderately flat, angled at top of scrobes and face straight to mouth margin, face below top of scrobes forming and angle of about 60° with the tangent of the frontovertex; occipital margin sharp, sometimes weakly carinate, a conspicuous long seta present on margin behind each posterior ocellus; a short oval depression adjacent to each eye on occipital margin; scrobes shallow, indistinctly margined, narrowly ∩-shaped; antenna with scape about 3.5-3.8X as long as broad; funicle 4-segmented, segments strongly transverse to hardly longer than broad; clava longer than funicle, 3-segmented, sutures parallel, apically pointed or rounded, sensory area at apex only; eye slightly overreaching occipital margin, clothed with moderately conspicuous setae; malar sulcus absent; mandible with four teeth, two upper teeth short, and a distinct ventral peg ( Fig. 64, arrowed), palp formula 4-3.

Thorax with pronotum hardly exposed behind head, its posterior margin broadly V-shaped and strongly emarginate medially; mesoscutum quite flat; scutellum about 1.2-1.6X as broad as long, flat, with reticulate sculpture that is much deeper than that on mesoscutum, side and apex completely smooth and shiny, apex with one or two pairs of erect, bristle-like or scale-like setae; submarginal vein with a subapical hyaline break, parastigma slightly swollen, narrowly subtriangular with a single, longer erect, backward facing seta; marginal vein about 5-6X as long as broad, about 2X as long as postmarginal or stigmal veins; filum spinosum present as a line of 4 or 5 stouter setae; mesopleuron expanded posteriorly, but not quite reaching level with posterior margin of propodeum; propodeum with some irregular sculpture surrounding spiracle extended posteriorly as troughs and ridges towards hind coxa.

Gaster with hypopygium reaching about half way to two-thirds towards apex, transverse, subrectangular; last tergite about as long as mid tibia; ovipositor slightly exserted, slightly longer than mid tibia and about 4X as long a gonostylus.

Male. Length about 0.7-0.9mm.

Generally very similar to female except for structure of antenna and genitalia, antenna with scape about 3.5X as long as broad, funicle 2-segmented, both segments anelliform and without linear sensilla; clava about 6.5X as long as broad and 3X as long as pedicel and funicle combined, apex pointed with a short finger-like projection; flagellum clothed in setae that are about half as long as diameter of segments; phallobase about 4-5X as long as broad, paramere with a very short subapical seta, cuspis seta present; digitus about 2X as long as broad with single apical hook; aedeagus slender about 12X as long as broad, about 0.5X as long as mid tibia and with apex acute.

DISTRIBUTION. Virtually cosmopolitan, but absent from higher latitudes (about 40°+). Not yet recorded from the Afrotropical region or Australia.

HOSTS. Species have been recorded as primary parasitoids of a variety of armoured scales, including species of the genera Aonidiella Berlese & Leonardi , Aspidiotus Bouché , Aulacaspis Cockerell , Clavaspis MacGillivray , Diaspis Costa, and Hemiberlesia Cockerell ( Hemiptera : Diaspididae ); also recorded from Ceroplastes Gray , Parasaissetia Takahashi , Saissetia Deplanche ( Coccidae ) and Aleurothrixus Quaintance & Baker ( Aleyrodidae ) and, probably erroneously, from mealybugs ( Pseudococcidae ) (see Noyes, 2019).

BIOCONTROL. Plagiomerus diaspidis Crawford was imported from Tenerife (Canary Islands, Spain) and released experimentally as a biological control agent against Diaspis echinocacti (Bouché) ( Hemiptera , Diaspididae ) within a glasshouse in south-eastern France but it failed to provide control. A second unidentified species of Plagiomerus (possibly hospes ) was found in a wet tropical greenhouse in the same region of France and was thought to be a potential biocontrol agent of Diaspididae . However, it failed to control any of the three species of diaspidids present ( Panis & Pinet, 2001).

COMMENTS. See comments under Homalopoda (p. 54).

IDENTIFICATION. Worldwide, 11 species, including the species described below as new, see: Hayat 2006 (2 species, India); Xu & Huang, 2004 (4 species, China); single species treatments: Si et al, 2010 ( China); Ashmead, 1888 ( USA); Girault, 1915b ( Peru).