Grotea ambarosa sp. nov. is described, illustrated and compared to currently described species of the genus. The new species is characterized mainly by having the mesosoma 2.9× as long as high; genal projection distinct and apically subquadrate; pleural carina distinct only anteriorly to anterior transverse carina; mesosoma almost entirely amber-orange and legs with complex dark brown and white marks. This is the first record of any labenine species for the Greater Antilles; the few distribution records elsewhere in the Caribbean Islands are reviewed and discussed in the context of the biogeography of Labeninae.

Caribbean Islands, biogeography, Darwin wasp, ichneumonid

Labeninae are a relatively small subfamily of ichneumonid wasps, currently with 12 genera and 163 extant species (Yu et al. 2016 and additions in Herrera-Flórez 2018 and Herrera-Florez and Penteado-Dias 2019). Genera within Labeninae exhibit a diverse range of morphologies but share the following putative synapomorphies: an apically truncated vein Sc in the hind wing; a uniformly weakly sclerotized proctodeal membrane; the ventral valve of the ovipositor enclosing the dorsal valve; and a basally lobate ovipositor sheath (Gauld 2000). In addition, species of Labeninae have a distinct areolet on the front wing, cylindrical flagellum, simple tarsal claws, slender hind coxa, and first tergite and sternite usually fused (Townes 1969; Gauld 1991). The subfamily historically has been known to have a mainly “Gondwanan” distribution: almost all species occur in the Australasian and Neotropical regions, with a few species of Labena and Grotea found in the Nearctic region (Gauld and Wahl 2000).

Grotea Cresson is a moderately diverse genus of labenines characterized by the rather elongate and slender body; clypeus with apical margin distinctly concave; lower part of gena usually strongly raised into a lamella or process; hind wing with about 6–8 basal hamuli on vein C; and sternite 1 extending far past the level of spiracle of tergite 1 (Gauld 2000). Species of Grotea are cleptoparasitoids of bees that build nests in hollow twigs, including species of Ceratina Latreille, Megachile Latreille, Chilicola Spinola, and Manuelia Vachal (Daly et al. 1967; Packer 2004; Gonzalez and Giraldo 2009). The adult female oviposits through the wall of the twig into the cell, and after eclosing the wasp larva consumes both the bee larva and its pollen reserves, sometimes going through the contents of multiple cells.

The genus currently includes 26 species broadly distributed in the New World, from Canada to southern Chile (Slobodchikoff 1970; Gauld 2000; Herrera-Florez 2014; Herrera-Florez and Penteado-Dias 2019). However, there are no records for the genus, and in fact for any species of Labeninae, from the Greater Antilles. Herein we describe a new species of Grotea from the Dominican Republic, providing the first record of the subfamily for this region.

The type series is deposited in the Utah State University Insect Collection (USUC); comparative material for other species of Grotea was obtained from USUC as well as the American Museum of Natural History (AMNH); Instituto Nacional de Pesquisas da Amazônia (INPA) and the National Museum of Natural History (USNM).

Morphological terminology follows Broad et al. (2018). Proportions of the mesosoma (length vs. height) were calculated by measuring length from the point at which the pronotum meets the cervical shield to the posterior basal angle of the metapleuron (i.e. “Weber’s length”, Weber 1938) against the distance from the midcoxal attachment to the dorsal apex of the scutellum (Fig. 1). Leg surfaces were interpreted as in Aguiar and Gibson (2010). When potentially ambiguous, color names are followed by their respective RGB formula, as determined from digital pictures of the studied specimens, according to procedures described by Aguiar (2005).

Specimens were examined using a Leica Wild Stereo/Dissecting M10 microscope. Images were prepared using a modified version of the EntoVision suite (GTVision, Hagerstown, Maryland), including a Leica Z16 zoom lens attached to a digital video camera that feeds image data to a desktop computer, with a custom fabricated illumination dome (RK Science Factory, Vitória, Brazil). Stacks of photos were combined in a single image using Zerene Stacker (Zerene Systems, Richland, WA, USA).

This is the first record of Grotea, or in fact any labenine genus, in the Greater Antilles (Fig. 7). A few labenine species are recorded from islands in the Atlantic Ocean: Labena nigra Rohwer in Bermuda (Rohwer 1920), L. trilineata Ashmead in Grenada (Ashmead 1900) and the predominantly South American G. delicator Thunberg with records from Trinidad and Tobago (Slobodchikoff 1970) and a nonspecific record to the Leeward Islands (i.e. northern islands of the Lesser Antilles chain, from the Virgin Islands to Guadeloupe; Slobodchikoff 1970).

Figure 7. 

Diagram showing type locality for Grotea ambarosa sp. nov.

It has been repeatedly suggested that the Labeninae have originated in Gondwana after its separation from Laurasia, but before the landmasses of South America and Australia split from each other (e.g. Gauld 1983; Wahl 1993; Gauld 2000; Gauld and Wahl 2000; but see Spasojevic et al. 2018). If that is the case, the occurrence of Labeninae in the Greater Antilles would likely be due to overwater dispersal. The occurrence of some species in rather remote landmasses (e.g. Bermuda, or Certonotus fractinervis (Vollenhoven) in New Zealand) seems to indicate that labenines can be relatively good dispersers, making their absence from the Greater Antilles until now rather surprising. This study reveals that labenines do indeed occur in this region, suggesting that the lack of labenine species was due to a deficit in collecting and taxonomic studies rather than to a real faunal depletion. We predict that yet other species of Labeninae remain undiscovered in the Greater Antilles.

This work was supported by the National Science Foundation (REU Site, EAR-1062692, OCE-1560088) through funding to the NMNH’s Natural History Research Experiences (NHRE) program. Special thanks to Gene Hunt and Virginia Power (NMNH) who run this program. Daniell Fernandes (INPA) provided help with literature on distribution records of Labeninae. Seán Brady (NMNH) hosted the first author as an intern at the NMNH and provided logistical help and good advice. David Wahl (USUC) kindly received the second author in a visit to his institution and provided a generous loan of labenine specimens. The authors have declared no competing interests exist.