A new species of the genus Gonatopus Ljungh from the USA (Hymenoptera, Dryinidae)

Abstract A new species of Gonatopus Ljungh, 1810 is described from the USA, Florida: G. jacki sp. n. Morphologically, the new species is similar to G. ashmeadi Kieffer, 1905 and G. agropyrus Fenton, 1921, but it is distinguished by the different shape of the mesoscutum (very slender in G. jacki; broader in G. ashmeadi and G. agropyrus). Published identification keys to the Nearctic species of Gonatopus are modified to include the new species.

In 2015, additional specimens of Gonatopus from the USA were examined and the new species found is described herein.

Materials and methods
The descriptions follow the terminology used by Olmi (1984), Olmi and Guglielmino (2010), and Olmi and Virla (2014). The measurements reported are relative, except for the total length (head, except antennae, to abdominal tip), which is expressed in millimeters. In the descriptions, POL is the distance between the inner edges of the two lateral ocelli; OL is the distance between the inner edges of a lateral ocellus and the median ocellus; OOL is the distance from the outer edge of a lateral ocellus to the compound eye; OPL is the distance from the posterior edge of a lateral ocellus to the occipital carina; and TL is the 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 "propodeum" sensu Olmi (1984Olmi ( , 1994, Xu et al. (2013), Olmi and Virla (2014), and Olmi and Xu (2015).
The types of all Nearctic and Neotropical species of Gonatopus have been previously examined by the authors.
The material studied in this paper is deposited in the Department of Agriculture and Forestry Sciences, University of Tuscia, Viterbo, Italy (MOLC).
The description of the new species is based on the study of 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.

Hosts. Unknown.
Etymology. The species is named after the collector, John T. (Jack) Longino.

Remarks.
The new species is similar to G. ashmeadi Kieffer in Kieffer &Marshall, 1905 andG. agropyrus Fenton, 1921, by having head mostly brown, labial palpus bisegmented, mesoscum with no lateral pointed apophyses, meso-metapleural suture obsolete, first abdominal tergum transversely striate, protarsomere I shorter than IV, protarsomere V with lamellae situated in distal half. The main difference among G. jacki and the other two species is in the mesoscutum shape: very slender in G. jacki (Fig. 1A); broader in G.ashmeadi (Fig. 1C) and G. agropyrus (Fig. 1E). The comparison of the holotypes of the above three species shows also a difference regarding the colour: mostly black in G. jacki (Fig. 1A, B), yellow-testaceous in G. agropyrus (Fig. 1E) and testaceousferruginous in G. ashmeadi (Fig. 1C, D). However, these differences are not significant, because the colour can be very variable, so that mostly black specimens are known in both G. agropyrus and G. ashmeadi. Following the description of G. jacki, the key to the females of the Nearctic species of Gonatopus group 7 published by Olmi (1993b) can be modified by replacing couplet 14 as follows:

Conclusions
Olmi (1984, 1987, 1992, 1993a, 1993b, 1995, 2003) and Olmi and Guglielmino (2013) listed 51 Gonatopus from the Nearctic region. With the description of the above new species the number of species now known in the USA is 52. In comparison with the 135 species listed in Mexico (Moya Raygoza and Olmi 2010), the dryinid fauna of the USA is poorly known, as is that of Canada (18 listed species). A similar situation exists also regarding the hosts: they are known only in 26 species ).