Gonatocerus Nees 1834

Genus Gonatocerus Nees ab Esenbeck, 1834

Gonatocerus Nees ab Esenbeck 1834: 192 –193. Type species: Gonatocerus longicornis Nees ab Esenbeck, by monotypy. Subsequent taxonomic references: Girault 1911: 273 –277 (North American species); Kryger 1934: 503 –505 (nomenclatural remarks); De Santis 1967: 102–103 (catalog); Bouček & Graham 1972: 125 –130 (genus and type species identity); De Santis 1979: 364 (catalog); Sahad & Hirashima 1984: 7 –11 (Japanese species); Schauff 1984: 36 –37 (genus definition); Matthews 1986: 214, 216 (species groups and British species); Huber 1986: 220 –222 (historical review, host records, etc.); Huber 1988: 5 –7, 23–24, 29–30 (species groups and Nearctic species of two groups); Noyes & Valentine 1989: 34 –35 (diagnosis and remarks on New Zealand species); Yoshimoto 1990: 36 –42 (species groups and list of Western Hemisphere species); Zeya & Hayat 1995: 52 –59 (species groups and Indian species); Huber & Beardsley 2000: 51 –53 (species in Hawaiian Islands); Baquero & Jordana 2003: 3 –5 (diagnosis, key to species groups and species in Navarre, Spain); Donev 2005: 376 –377 (key to species groups in the Balkan Peninsula); Triapitsyn 2006a: 4–6 (key to Nearctic egg parasitoids of Proconiini); Lin et al. 2007: 34 –37 (short diagnosis, list of Australian species); Luft Albarracin et al. 2009: 8 –10 (list of species, distribution, references, and host associations in Argentina), 13 (key), 16 (illustration).

Lymaenon Walker 1846: 49 –50. Type species: Lymaenon acuminatus Walker, by subsequent designation by Gahan & Fagan 1923: 82. Synonymized under Gonatocerus by Foerster 1856: 118 and Bouček & Graham 1972: 127; treated as a subgenus of Gonatocerus by Herting 1972: 14, and as a valid genus by Kryger 1934: 503, Debauche 1948: 78 – 113 (species groups and Belgian species), Debauche 1949: 25 –59 (species groups and African species), Kryger 1950: 68 –71 (historical review), and Annecke & Doutt 1961: 4 (key), 13 (diagnosis, distribution, subgenera).

Rachistus Foerster 1847: 203. Type species: Ooctonus litoralis Haliday, by subsequent designation by Gahan & Fagan 1923: 128. Synonymized under Gonatocerus by Foerster 1856: 119 and Bouček & Graham 1972: 127, and under Lymaenon by Debauche 1949: 25.

Rhachistus Dalla Torre 1898: 429. Unjustified emendation of Rachistus Foerster.

Cosmocomoidea Howard 1908: 68. Type species: Cosmocomoidea morrilli Howard, by monotypy. Treated as a synonym of Ooctonus Haliday by Girault 1929: 20, as a subgenus under Lymaenon by Ogloblin 1959b: 50 –56 and Annecke & Doutt 1961: 4, and synonymized under Gonatocerus by Bouček & Graham 1972: 127.

Oophilus Enock 1909: 458. Type species: Oophilus longicauda Enock, by monotypy. Synonymized under Gonatocerus by Girault 1911: 276 –277 and Bouček & Graham 1972: 127, and under Lymaenon by Debauche 1949: 25. Treated as separate genus by Kryger 1950: 79 –81.

Agonatocerus Girault 1913a: 276. Type species: Agonatocerus humboldti Girault, by original designation. Synonymized under Gonatocerus by Girault 1915a: 156 and Bouček & Graham 1972: 127, and under Lymaenon by Debauche 1949: 25.

Gonatoceroides Girault 1913b: 255 (as subgenus of Gonatocerus). Type species: Gonatocerus (Gonatoceroides) australicus Girault [as australica], by original designation. Synonymized under Gonatocerus by Girault 1915a: 156 and Bouček & Graham 1972: 127, and under Lymaenon by Debauche 1949: 25.

Gastrogonatocerus Ogloblin 1935: 65 (as subgenus of Gonatocerus). Type species: Gonatocerus (Gastrogonatocerus) membraciphagus Ogloblin, by original designation. Treated as a subgenus of Lymaenon by Ogloblin 1938a: 93 –106 (in part) and Annecke & Doutt 1961: 4, and synonymized under Lymaenon by Debauche 1949: 25 and under Gonatocerus by Bouček & Graham 1972: 127.

Gahanopsis Ogloblin 1946: 286, 288 (as subgenus of Lymaenon). Type species: Lymaenon (Gahanopsis) deficiens Ogloblin, by original designation. Syn. n.

Decarthrius Debauche 1949: 21 –22. Type species: Decarthrius straeleni Debauche, by original designation. Synonymy under Gahanopsis by Annecke & Doutt 1961: 13. Syn. n.

Diagnosis. The following combination of features will separate all Gonatocerus from similar looking genera (those with 8 or 7 funicle segments in females). Both sexes: forewing relatively wide, with posterior margin convex; marginal vein with two macrochaetae and the hypochaeta about midway between them; tarsi 5-segmented. Female: antenna with 8 or, rarely, 7 funicle segments; gastral segment 1 similar in length to segment 2. Male: antenna with 11 flagellomeres; genitalia not encapsulated in a tubular capsule or phallobase; instead, aedeagus attached directly to the apical sternum, with two long apodemes united distally (V-shaped) and a long median apodeme.

Classification. Gonatocerus is a relatively easily recognized genus, so any generic key to the Mymaridae may be used for its recognition in the Neotropical region: Annecke & Doutt (1961) for the world genera, Yoshimoto (1990) for the New World genera, and Luft Albarracin et al. (2009) for the genera in Argentina.

The place of Gonatocerus within the higher classification of Mymaridae and its relationships with other genera were first discussed by Schauff (1984), who hypothesized Gonatocerus + Ooctonus Haliday were the most basal clade of Mymaridae next to the Alaptus group and other genera with 5-segmented tarsi. Viggiani (1989) classified Gonatocerus (as Lymaenon Walker) in the tribe Lymaenonini Ghesquière of the subfamily Lymaenoninae based solely on external male genitalic characters. Huber (2002) placed Gonatocerus + Gahanopsis Ogloblin as part of an unresolved trichotomy with other mymarids lacking a postmarginal vein. Lin et al. (2007) then placed Gonatocerus in a separate Gonatocerus group of genera, and we concur with that preliminary placement. Until all the mymarid genera are thoroughly revised it would be premature to here indicate the proper placement of Gonatocerus within Mymaridae.

Distribution. Cosmopolitan.

Hosts. In the Neotropical region, reliable host records of Gonatocerus spp. are from eggs of Aetalionidae, Cicadellidae, and Membracidae (Hemiptera: Membracoidea). These and most extralimital records were listed by Huber (1986); however, many non-membracoid records need confirmation.

Species groups within Gonatocerus. The large number of species within the genus and their considerable diversity led earlier workers to subdivide Gonatocerus into subgenera or species groups, as summarized in Table 1. Several of the species groups were either not defined or, when defined, were discovered by subsequent workers to contain a mixture of species that should properly have been placed in a different species group or more than one other species group. Conversely, two or more groups sometimes turned out to contain species better placed in one and the same group. In addition, the names of some of the groups were changed by subsequent workers. The subgenera recognized by Ogloblin (1935, 1946, 1959b) were either not used by other workers, except Annecke & Doutt (1961), or were subsumed under particular species groups. Confusion at the species group/subgenus level thus existed for several decades. Matthews (1986) resolved some of the problems, and proposed using three groups for the European fauna: the ater, litoralis, and sulphuripes groups. Huber (1988) proposed three more species groups, the membraciphagus, deficiens, and straeleni groups. The latter two groups were proposed for the two species in Gahanopsis Ogloblin without formally synonymizing Gahanopsis under Gonatocerus. Yoshimoto (1990) and Zeya & Hayat (1995) subsequently proposed the masneri species group and the asulcifrons species group, respectively.

In the revised classification we propose, several of the species groups are given subgeneric status, which better reflects the morphological diversity within Gonatocerus. Within the large and diverse subgenus, G. (Cosmocomoidea), we also recognize and define or redefine several species groups, which were partly treated by Huber (1988) as subgroups within the ater species group.