A new species of Dryinus Latreille, 1804, is described from Georgia (USA). D. georgianus sp. nov. is morphologically similar to D. mexicanus (Perkins, 1907) and D. splendidus Guglielmino and Olmi, 2013, but is distinguished by the lateral ocelli not touching the occipital carina (in the other two species, the lateral ocelli touch the occipital carina). The key to the females of the Nearctic species of Dryinus group 1 is modified to include the new taxon.

Chrysidoidea, Dryininae, Georgia, Sapelo Island, taxonomy, key, Nearctic region, Dryinus georgianus, Dryinus mexicanus, Dryinus splendidus

Dryinidae is a small family of Chrysidoidea (Hymenoptera) including 16 subfamilies, 50 genera, and approximately 1900 species worldwide (Olmi and Xu 2015; Tribull 2015; Olmi et al. 2019). The species of this family are parasitoids and often also predators of Hemiptera Auchenorrhyncha (Guglielmino et al. 2013).

Dryinidae of the Nearctic region were studied mainly by Olmi (1984) and Guglielmino and Olmi (2013). In this region, the genus Dryinus Latreille, 1804, includes 20 species (Guglielmino and Olmi 2013; Olmi 1984, 1991, 1996, 2010, 2011; Ponomarenko 1981), among which only the following three species are recorded from Georgia, USA: D. alatus (Cresson, 1872) (Guglielmino and Olmi 2013; Olmi 1984), D. testaceus (Olmi, 1984) (unpublished record: Monroe Co., Forsyth, 1.VII.2000, 1 female in RAM), and D. inconsultus (Olmi, 1984) (unpublished record: Monroe Co., Forsyth, 18–23.V.1970, 1 female in CNC). All the above three species, including D. alatus, are known in Georgia only from one locality: Forsyth, in Monroe Co. In 2017 the authors examined a Dryinus specimen collected in Georgia and discovered a new species, described below.

The description follows the terminology used by Guglielmino et al. (2016a, 2016b, 2018) and Guglielmino and Olmi (2013). The measurements reported are relative, except for the total length (head to abdominal tip, without the antennae), which is expressed in millimetres. In the descriptions the following abbreviations are used:

POL distance between the inner edges of the lateral ocelli;

OL distance between the inner edges of a lateral ocellus and the median ocellus;

OOL distance from the outer edge of a lateral ocellus to the compound eye;

OPL distance from the posterior edge of a lateral ocellus to the occipital carina;

TL distance from the posterior edge of an eye to the occipital carina.

The term “metapectal-propodeal complex” is here used in the sense of Kawada et al. (2015). It corresponds to the term “metathorax + propodeum” sensu Olmi (1984), Olmi and Virla (2014), Olmi and Xu (2015) and Xu et al. (2013). The terms “metapectal-propodeal disc” and “propodeal declivity” sensu Kawada et al. (2015), used here, correspond to the terms “dorsal surface of propodeum” and “posterior surface of propodeum”, sensu Olmi (1984), Olmi and Virla (2014), Olmi and Xu (2015) and Xu et al. (2013).

The term “ADOs” (= Antennal Dorsal Organs) is here used in the sense of Riolo et al. (2016). It corresponds to the term “rhinaria” sensu Olmi (1984, 1994), Olmi and Virla (2014), Olmi and Xu (2015) and Xu et al. (2013). According to Riolo et al. (2016), ADOs are sensory structures, that might mediate the antennal responses to vibratory stimuli. As far as we know, they are present only in antennae of dryinid females attacking Fulgoromorpha (Olmi 1984, 1991, 1994).

The names of cells and veins of the forewing are here used in the sense of Azevedo et al. (2018). In all previous monographs on Dryinidae (Olmi 1984, 1994; Olmi and Virla 2014; Olmi and Xu 2015; Xu et al. 2013) different names were used. The correspondence between old and new names is the following (the first name is the old name): median cell = radial cell (R); submedian cell = first cubital cell (1Cu); stigmal vein = second radial cross & radial sector (2r-rs&Rs). In the text, cells and veins will be named by their respective abbreviations, including costal cell (C). The terminology of tegument sculpture follows Olmi and Virla (2014).

The types of all Nearctic species of Dryinus were examined. The holotype of the new species studied in this paper is deposited in the Royal Alberta Museum, Edmonton, Alberta, Canada (RAM). Other examined species from Georgia (USA) are deposited in the Canadian National Collection of Insects, Ottawa, Canada (CNC).

The description of the new species is based on the study of only a single specimen. The authors are aware that descriptions of new taxa should normally be based on more individuals. However, Dryinidae are so rare that it is uncommon to collect more than one specimen of each species. In addition, on the basis of the experience and knowledge of the authors, the new species is sufficiently delimited by unique characters to justify its description.

The female of the new species has complete notauli (Fig. 1A) and enlarged claw provided with one strong subapical tooth (Fig. 2). Because of these characters, D. georgianus belongs to group 1 of Dryinus, according to the systematics proposed by Olmi and Virla (2014). In this species, the head is ferruginous (Fig. 1A, C); the mesoscutum is granulate and partly reticulate rugose, notauli complete (Fig. 1A) and the enlarged claw is spatulate (Fig. 2). Because of these characters, D. georgianus is similar to D. mexicanus (Perkins, 1907) and D. splendidus Guglielmino and Olmi, 2013, recorded respectively from Mexico and USA (Guglielmino and Olmi 2013). However, in D. georgianus the lateral ocelli do not touch the occipital carina (Fig. 2), whereas in the other two species they do. The key to the females of the Nearctic Dryinus group 1 presented by Guglielmino and Olmi (2013), should be modified by replacing couplet 8 as follows:

Among the Dryinus species recorded from Georgia, D. alatus and D. georgianus belong to group 1, whereas D. testaceus and D. inconsultus belong respectively to groups 2 and 3.

Dryinus species are known to parasitize hosts belonging to the following families of Fulgoromorpha (Guglielmino et al. 2013): Acanaloniidae, Cixiidae, Dictyopharidae, Flatidae, Fulgoridae, Issidae, Lophopidae, Ricaniidae, Tropiduchidae. Larvae of Dryinus were described by Abril-Ramírez (1992) and Guglielmino et al. (2015).

Many thanks to Dr Matthias Buck (Invertebrate Zoology, Royal Alberta Museum, Edmonton, Alberta, Canada) for the loan of the specimen described in this paper. The authors are very grateful to Mr. Leonardo Capradossi (Tuscania, Italy) for the multifocal pictures of the new species and Mr. Bob Zuparko (Essig Museum of Entomology, University of California, Berkeley, California, USA) for his suggestions about the English language of this paper. This research was carried out in the framework of the MIUR (Italian Ministry for Education, University and Research) initiative “Department of excellence” (Law 232/2016).