Tropicolabus Heinrich, 1959

Dal Pos, Davide, Heilman, Victoria & Welter-Schultes, Francisco, 2022, Platylabini (Hymenoptera: Ichneumonidae: Ichneumoninae) of the south-eastern United States: new distributional data, taxonomic notes, illustrated keys, and an annotated catalogue of the genera and species, Journal of Natural History 56, pp. 1869-1938 : 1925-1927

Tropicolabus Heinrich, 1959

Tropicolabus Heinrich, 1959: 216 .

Type species Platylabus foxi Davis, 1898 , by original designation.

Comparative diagnosis

Heinrich (1959, p. 216), and later Heinrich (1962b, p. 754), specified that Tropicolabus differed from Platylabus because of the ‘upwards curbed [sic] apophyses of the propodeum’, a character shared instead with Ambloplisus . After a careful examination of the type species and the first female, it is safe to conclude that the upward apophyses are in fact simply tooth-like projections formed by the conjunction of the strongly lamellate propodeal carinae ( Figure 37b ). This character can be seen in several other Platylabini species (e.g. Platylabus clarus ), and does not constitute apophyses as in the case of Ambloplisus ornatus ( Figure 37a ) or as delineated by Ronquist and Nordlander (1989). Therefore, the primary diagnostic character proposed by Heinrich (1959) during the establishment of the new genus does not allow an unambiguous separation between Tropicolabus and Platylabus . However, we do not feel the need to synonymise the two genera (and therefore restore the original combination for the species), to avoid further complications within the tribe. For the purpose of this contribution, Tropicolabus can be easily separated from Platylabus employing other characters, one of which was not previously mentioned by Heinrich (1959, 1962b). According to our examination, Tropicolabus can be distinguished from Platylabus by the following combination of characters: presence of twisted mandibles, appearing unidentate in frontal view (bidentate in Platylabus ); the predominantly smooth and shining mesoscutum, with dense punctures only in the anterior half ( Figure 36b ); and lamellate propodeal carinae ( Figure 37b ) (never lamellate in Platylabus ).

The misinterpretation of the propodeal tooth-like projection also impacts the separation between Tropicolabus and Ambloplisus , which can now be easily distinguished by the following characters: the tooth-like propodeal carinae ( Figure 37b ) (and not long apophyses as in Aploplisus, Figure 37a ); the strongly impressed gastrocoeli and thyridia as large as or larger than the space between them, the strong and large gastrocoeli ( Figure 36c ) (superficial and small in Amploplisus, Figure 5d ); the broad genae in frontal view ( Figure 38b ) (convergent in Ambloplisus , Figure 38a ); temples roundly narrowed in dorsal view ( Figure 39b ) (steeply, almost concavely narrowed in Ambloplisusi, Figure 39a ) the propodeum with the area superomedia separated from the area basalis ( Figure 37b ) (a single elongate area in Ambloplisus , Figure 5c ).

Range and diversity

The genus is monotypic and, so far, has been recorded only in the Nearctic, even though some comments in Santos et al. (2021, supplement S8) seem to confirm its presence in Costa Rica (unpublished material). Heinrich (1962b, p. 755) already hypothesised a more tropical distribution of the genus based on the rich yellow colour pattern on the thorax, typical of Neotropical species. Prior to this contribution, the genus was known only for the north-eastern United States and only from the type locality .

Figures

Figure 5. Ambloplisus ornatus (Cresson, 1868), ♀. a) Habitus, lateral view. b) Head, frontal view. c) Head and mesosoma, dorsal view. d) Propodeum and metasoma, dorsal view.

Figure 36. Tropicolabus foxi (Davis, 1898), ♀. a) Habitus, lateral view. b) Mesoscutum and head, dorsolateral view. c) Metasoma, dorsal view.

Figure 37. Propodeum and metasoma, dorso-lateral view. a) Ambloplisus ornatus (Cresson, 1868). b) Tropicolabus foxi (Davis, 1898).

Figure 38. Face, frontal view. a) Ambloplisus ornatus (Cresson, 1868), holotype ♀. b) Tropicolabus foxi (Davis, 1898), holotype ♀.

Figure 39. Head, dorsal view. a) Ambloplisus ornatus (Cresson, 1868), ♀. b) Tropicolabus foxi (Davis, 1898), ♀.