Genus ADELENCYRTUS Ashmead

Adelencyrtus Ashmead, 1900:401. Type species: Encyrtus chionaspidis Ashmead, by original designation.

Epiencyrtoides Girault, 1915a:108. Type species: Epiencyrtoides quadridentatus Girault, by original designation. Synonymy with Adelencyrtus by Mercet, 1921:698.

Epitetracnemus Girault, 1915a:164. Type species: Epitetracnemus sexguttatipennis Girault, by original designation. Synonymy with Adelencyrtus by Japoshvili et al., 2016:349-350.

Anabrolepis Timberlake, 1920:431. Type species: Anabrolepis extranea Timberlake, by original designation. Synonymy with Epitetracnemus by Noyes & Hayat, 1984:273. syn.nov.

Rotrencyrtus Risbec, 1939:59. Type species: Rotrencyrtus depressus Risbec, by monotypy. Synonymy with Adelencyrtus by Annecke & Insley, 1971:2,39.

Female. Overall length about 1.1-1.7mm.

Body dark brown with a metallic sheen.

Head acutely triangular in profile with frontovertex more or less flat and forming an angle of about 60° with the face; occipital margin sharp, not carinate; frontovertex generally about 0.20- 0.25X as wide as head and with a slender, broadly oval depression adjacent to eye behind posterior ocellus near occipital margin; mandible with four teeth, lower teeth longest, upper teeth usually short, sometimes very short and almost forming a weakly denticulate truncate margin; mandible with a distinct, socketed, peg-like structure present on inner surface near lowest margin; palp formula 4-3; scape hardly broadened and flattened, about 3.5-4.5X as long as broad; flagellum subcylindrical; funicle 6-segmented with segments transverse to slightly longer than broad, sometimes all transverse or all longer than broad, proximal segments generally smallest; clava 3-segmented with sensory area small, apex rounded.

Thorax dorsally flattened; pronotum with posterior margin emarginate, broadly V-shaped; sculpture on mesoscutum polygonally reticulate to imbricate reticulate and shallower than sculpture on scutellum; scutellum about 1.2X as broad as long, with fine, regular, punctate reticulate to longitudinally elongate polygonally reticulate sculpture, side and apex smooth and shiny; mesopleuron extending to, or nearly to, posterior margin of propodeum; tarsi 5-segmented; mid tibial spur about as long as basitarsus; wings always fully developed; fore wing about 2.4- 2.5X as long as broad; hyaline or infuscate with hyaline areas; marginal vein about 3.0-5.5X as long as broad, longer than stigmal vein, postmarginal vein slightly shorter than stigmal vein, rarely longer.

Gaster about as long as thorax; hypopygium reaching about half way along gaster; ovipositor with gonostylus freely articulated, exserted part usually less than length of mid tibial spur.

Male. Length about 0.8-1.0mm.

Similar to female but for wider frontovertex, hyaline fore wing and structure of antenna and genitalia; head about 2X as wide as frontovertex, antenna with 2 anelliform funicle segments and a long clava that is about 7-8X as long as broad and about as long as head width; genitalia with aedeagus slender, digiti well developed, each about 2X as long as broad with a single apical hook.

DISTRIBUTION. Cosmopolitan.

HOSTS. Almost exclusively solitary endoparasitoids of armoured scale insects (Hemiptera: Diaspididae), although possibly also of early instars of soft scale insects (Hemiptera: Coccidae) (see A. bifasciatus below). One species, Adelencyrtus subapterus (Kurdjumov), has been recorded as a parasitoid of Rhizococcus greeni (Newstead) (Hemiptera: Eriococcidae) on Agropyron repens L. (Poales: Poaceae), but this parasitoid species does not belong to Adelencyrtus.

BIOCONTROL.Four species of Adelencyrtus (chionaspidis (Howard), intersectus (Fonscolombe), oceanicus (Doutt), odonaspidis Fullaway) have been used in biocontrol projects for the control of various species of diaspidid scales, but none of these has been successful. Most introductions failed to establish and those that did, failed to provide effective control (see Noyes & Hayat, 1994 and also below).

COMMENTS. Adelencyrtus is close to Habrolepis Förster, 1856, Ruskiniana Girault, 1923 and Neococcidencyrtus Compere, 1928, all four genera having a subcylindrical, six-segmented funicle and a distinct peg-like structure on inner surface of the mandible near the lowermost margin. Adelencyrtus can be separated from the three other genera by the mandible having four teeth (although the two uppermost teeth may be very short almost forming a truncate surface). In Neococcidencyrtus the mandible is basically tridentate, but occasionally with a single lower tooth and a broad straight, upper truncation and in Habrolepis and Ruskiniana the mandible has one acute tooth and a broad, slightly concave truncation. Most species of Neococcidencyrtus have some areas of the body pale orange, all have the mid tibia with two brown bands. Species of Adelencyrtus are mostly dark brown with a metallic sheen and they have at most one brown band on the mid tibia. Habrolepis and Ruskiniana have not yet been found in the Neotropical region, but in most cases, they can be separated from Adelencyrtus by having either a pair of scale-like setae at the apex of the scutellum or a line of about 15 slender, scale-like setae near the apex, whereas in Adelencyrtus there is at most a pair of long, very slender apical setae. In those species of Habrolepis that lack scale-like setae at the apex of the scutellum the fore wing has an uninterrupted hyaline, subapical fascia as well as a pair of opposite hyaline spots. No species of Adelencyrtus is known to have an uninterrupted, subapical, hyaline fascia.

See also comments under Quetsira (p. 124).

IDENTIFICATION. Worldwide, 44 described species are currently placed in Adelencyrtus. Keys to some of these species are provided by Hayat, 2006 (10 Indian species); Zhang & Shi, 2010 (11 Chinese species as Adelencyrtus and 8 species as Epitetracnemus) and Trjapitzin, 1989 (Palaearctic species, 4 as Adelencyrtus and 3 as Epitetracnemus).