Pristomerus Curtis 1836
Creators: name: Rousse, Pascal
name: Noort, Simon van
Publisher: name: Zenodo
Year: 2015
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Hymenoptera
Ichneumonidae
Pristomerus

description: Genus Pristomerus Curtis, 1836
Pristomeridia Ashmead, 1900: 100.
Pristocelus Szépligeti, 1905: 48.
Neopristomerus Viereck, 1912: 592.
Nesanomalon Morley, 1913: 56.
Type species
Ichneumon vulnerator Panzer, 1799.
Diagnosis (updated from Gauld 2000)
Female
Small to moderate sized species, fore wing length 2–8 mm; main background colour yellow to black; head with mandible not twisted, without obvious ventral flange, teeth subequal to upper tooth slightly longer than lower tooth; palpi formula 5:4; frons biconcave, sometimes with a mid-longitudinal ridge that may be strongly raised; occipital carina mid-dorsally complete to narrowly obsolescent, ventrally joining hypostomal carina at to distinctly above mandible base; antenna with flagellum finely setose; inner margins of eyes from slightly converging to distinctly diverging ventrally; mesosoma punctate with smooth or coriaceous parts to extensively punctate; notaulus weakly to strongly impressed; pronotum unspecialized with epomia usually discernible and quite short; scutellum flat to moderately convex, without lateral carina; epicnemial and postpectal carinae complete; propodeum with carination usually complete, sometimes longitudinal carinae partially obsolescent; tarsal claws unspecialized, pectinate; mid tibia with two apical spurs; hind femur often with a ventral subapical tooth, often followed by auxiliary denticles; fore wing with areolet open (vein 3 rs-m absent); pterostigma stout, usually as broad or broader than 1 st subdiscal cell; distal abscissa of M from virtually absent to complete to wing margin; abscissa of M between rs-m and 2m-cu usually as long to far longer than rs-m, rarely distinctly shorter; hind wing with distal abscissae of Rs, M, Cu1 and 1A usually absent, almost invariably without a trace of the distal abscissa of Cu1 basally so that Cu&cu-a is not broken but smoothly curved; metasoma with tergites 1–2 usually aciculate and following ones coriaceous or granulate; first segment moderately stout, ventral margins of tergite 1 widely separated so that sternite 1 is exposed for its full length, glymma distinct in front of spiracle; tergite 2 slender to moderately stout, slightly depressed, with welldefined thyridium subcircular to elongate, close to anterior margin, at most separated from it by its own maximum diameter; laterotergite membranous and folded up; ovipositor 0.8–3.2× as long as hind tibia, straight to slightly down-curved but sometimes evenly bi-curved, its apex usually weakly to strongly sinuous but sometimes straight.
Male
Ocelli usually strongly enlarged, inner margins of eyes sometimes distinctly more convergent, mesoscutum sometimes strongly smoother, area superomedia sometimes more slender, hind femur stouter and femoral tooth stronger, nearly always present; gonosquama apically rounded, without distal lobe. Otherwise similar to female.
Differential diagnosis
Pristomerus is usually an easily identifiable ichneumonid genus, mostly defined by the presence of thyridia close to the anterior margin of tergite 2 and the separation of the ventral margins of tergite 1. Apart from a few exceptions, the apex of the ovipositor is also distinctly sinuous. This derived character is present in other ichneumonid and braconid subfamilies (Tersilochinae, Doryctinae, Braconinae …), and is probably an adaptation enabling the female to actively bend the ovipositor tip and thus to forage more efficiently within the host’s hideaway (Quicke 1991). The only other cremastine genus with comparable features is the Neotropical Xiphosomella Szépligeti,1905, in which the thyridia are distinctly removed from the anterior margin of tergite 2, and the ovipositor tip is rarely sinuous. Some extra-limital Xiphosomella cannot, however, be unambiguously separated from Pristomerus (Gauld 2000). When present, the femoral tooth is also a reliable feature, though many Pristomerus females lack it. The only other cremastine genus in the Afrotropical region with a ventral tooth on the femur is the Malagasy genus Fafana: in the only known Fafana Rousse, Villemant & Seyrig, 2011 species, the sculpture is almost entirely smooth, the distal abscissa of Cu1 reaches the hind wing margin and the ovipositor tip is straight.
Phylogeny
No comprehensive phylogenetic analysis of the subfamily Cremastinae has been published. The generic identification of Pristomerus is usually easy, but not one of the diagnostic morphological features may be unambiguously considered as a synapomorphy. The presence of thyridia (absent in most other cremastine genera), is considered as a plesiomorphic feature within Ichneumonidae (Gauld 1985). The sinuous ovipositor tip and the femoral tooth cannot be considered as derived characters, because they are not restricted to Pristomerus and are totally absent in some Pristomerus females. It is therefore impossible to ascertain whether the genus is monophyletic or not. Hence, Pristomerus is either a widespread and rather variable clade or part of a paraphyletic clade including Xiphosomella and other smaller cremastine genera.
Distribution, species richness and ecology
Including the three new synonyms and 31 descriptions in the present revision, the genus now comprises 140 species. This is a worldwide genus, most diversified in the tropics, which contain about two thirds of the currently known species. All known hosts are small lepidopterans (including several major pests) living in leaf rolls, tunnels, silk shelters or other concealed substrates. The biology of some widespread Pristomerus parasitizing agricultural pests has been documented: for example see Smith & Johnson (1986) and Cave (1995) for P. spinator (Fabricius, 1804), or Rosenberg (1934) and Athanassov et al. (1997) for P. vulnerator (Panzer).
description: Published as part of Rousse, Pascal & Noort, Simon van, 2015, Revision of the Afrotropical species of Pristomerus (Ichneumonidae: Cremastinae), with descriptions of 31 new species, pp. 1-129 in European Journal of Taxonomy 124 on pages 27-29, DOI: 10.5852/ejt.2015.124, http://zenodo.org/record/3780218