Revision of the genus Paralipsis Foerster, 1863 (Hymenoptera, Braconidae), with the description of two new species

Abstract The Palaearctic genus Paralipsis Foerster, 1863 (Hymenoptera: Braconidae: Aphidiinae) is revised and two new species are described: Paralipsis tibiator van Achterberg & Ortiz de Zugasti, sp. n. from Spain and Paralipsis planus van Achterberg, sp. n. from the Netherlands. Some biological notes are supplied for Paralipsis tibiator sp. n. A key to the four known species is added and all species are illustrated.


Introduction
The subfamily Aphidiinae (Hymenoptera: Braconidae) contains exclusively koinobiont parasitoids of ovoviviparous aphids (Aphididae sensu lato) (Yu et al. 2012;Shaw and Huddleston 1991). Few genera specialise on concealed hosts and Paralipsis Foerster, 1863, is one of them, by attacking root aphids associated with ants. The genus is restricted to the Palearctic region and only two valid species are known: P. enervis (Nees, 1834) (West Palaearctic) and P. eikoae (Yasumatsu, 1951) (East Palaearctic) (Yu et al. 2012). The detection of a new species of the genus in Spain by the second author triggered a revision of the genus and resulted in the discovery of a second new species from the Netherlands.

Material and methods
The second author detected the first Paralipsis tibiator sp. n. female during a routine myrmecological survey and conserved it in 70% ethanol. The following year, a focused search was undertaken to collect more Paralipsis by nest excavation and aspiration of the parasitoids. In addition, during two days, at haphazard moments, short (approx. 15 minutes) observations were conducted totalling about three hours. The specimens of P. planus sp. n. and P. enervis (Nees) were collected either in Malaise traps or in pitfall traps and conserved in 70% ethanol. The specimens were prepared using the AXA method (van Achterberg 2009;van Achterberg et al. 2010) and glued on card points or pinned on minutins. Observations and descriptions were made with an Olympus SZX11 stereomicroscope and fluorescent lamps. Photographic images were made with an Olympus motorized stereomicroscope SZX12 and processed with Adobe Photoshop CS5, mostly to adjust the size and background. The examined material is deposited in collection of the Naturalis Biodiversity Center (RMNH), Leiden. POL stands for the distance between both posterior ocelli and OOL for the distance between posterior ocellus and compound eye.

Biology
Ants constitute complex and well organized societies, which normally defence their nests viciously against intruders (Hölldobler and Wilson 1990). Nonetheless, several arthropods belonging to the class Arachnida or to main orders as Hymenoptera, Orthoptera and Coleoptera, have evolved to overcome this defence. As a result, symbiotic relationships ranging from mutualism, parasitism and commensalism to inquilinism occur in ant nests (Kistner 1982, Völkl et al. 1996. The case of the myrmecophilic aphidiine parasitoid wasp genus Paralipsis is more complicated, because they parasitise root aphids herded by ants (Takada and Hashimoto 1985). Once the parasitoid wasp infiltrates the ant colony, it finds a source of food (aphids) for its offspring protected by ants and thus sheltered from potential predators.
On 23 July 2014 two small wasps were seen in a nest of Lasius (Lasius) grandis Forel, 1909, located under a small rock at the foot of a Cedrus sp. (cedar) with abundant grass cover (lawn, Poaceae) at the Parque del Oeste (Madrid,Spain;40°25'55.8"N,3°43'43.7"W). Both wasps were occupying the galleries jointly with the ants; one was collected and the other one escaped flying. On 3 July 2015 in the same park (40°26'05.5"N, 3°43'27"W) a L. grandis nest at the foot of a Populus alba tree (white poplar), also covered with abundant Poaceae turf, was excavated and two additional females were collected. The following root aphids were found in the nest: an adult female of Tetraneura ulmi (Linnaeus, 1758), a nymph of T. nigriabdominalis (Sasaki, 1899), a nymph of Aploneura lentisci (Passerini, 1856) and two nymphs of Forda formicaria (von Heyden, 1837).
One female wasp was kept alive for two days along with ten ant workers of the same nest where the wasp was found. They were kept in a plastic container (8 cm × 8 cm × 3 cm) with supply of moisture and fed once with diluted honey. During this period, the wasp actively looked for the company of the ants. Upon disturbing the artificial nest, the wasp was always, and promptly, looking for a concentration of standing (not running) ants to join. Most of the time the wasp was hiding under the legs of the ants and sometimes walking around the group. The wasp was observed being frequently groomed and antennated by the ants. The wasp always showed a submissive behaviour and it was once observed actively antennating an ant, an action that elicited ant-wasp trophallaxis. While the first specimen was kept alive along with the ants, no wasp-ant rubbing such as is described by Takada and Yashimoto (1985) was observed. Probably, the rubbing behaviour was not observed because the chemical mimicry was already obtained.
In an ongoing study on aphid-ant relationships at a similar environment in Spain, so far L. grandis has been observed attending only F. formicaria root aphids (Pérez Hidalgo, pers. com.). During this study Paralipsis tibiator sp. n. has been observed parasitizing F. formicaria aphids being attended by L. grandis. It suggests that F. formicaria is the preferred host of Paralipsis tibiator sp. n., but we cannot rule out that other root aphids are chosen as hosts. Lasius grandis "is the most abundant species of the subgenus on the Iberian peninsula" (Seifert 1992) with a continuous distribution across the Iberian Peninsula (Gómez and Espadaler 2007). Also F. formicaria occurs all over the Peninsula (Nieto Nafria et al. 2003). Hence, it can be expected that Paralipsis tibiator sp. n. occurs in nests of L. grandis across the Iberian Peninsula.

Key to species of
Biology. Parasitoid of root aphids attended by the ants Lasius sakagamii Yamauchi & Hayashida, 1970or L. japonicus Santschi, 1941(Yu et al. 2012, Akino and Yamaoka 1998. Holotype male was collected from a nest of Lasius japonicus (published as L. niger; see Seifert 1992) in an old Cryptomeria japonica tree and the species was reared as parasitoid of the aphid Sappaphis piri Matsumura, 1918, on roots and subterranean stems of Artemisia princeps Pamp. (Takada 1976).
Distribution. Reported from Japan and Far East Russia (Yu et al. 2012).
Distribution. Reported from Andorra, Czech Republic, Finland, France, Georgia, Germany, Hungary, Kazakhstan, Macedonia, Moldova, Netherlands, Poland, Portugal, Romania, Slovakia, Spain, Sweden, UK and Serbia (Yu et al. 2012). The reports from Spain, Portugal and Andorra may concern P. tibiator sp. n. Diagnosis. Similar to P. enervis (Nees, 1834), but differs by the slenderer fore tarsus, the partly widened hind tibia and femur (Fig. 16) and the scapus distinctly widened dorsally in lateral view (vase-shaped: Fig. 17). Close to P. tibiator sp. n., but P. planus has the  vertex and mesoscutum shiny and with sparse short pubescence between long setae, the first tergite flat and shiny, its maximum width at level of spiracles of ♀ 0.7 times distance between spiracle and apex of tergite (Fig. 19), the mesopleuron shiny, the apical antennal segments with long erect setae (Figs 17,20), the fore basitarsus rather robust, the fifth antennal segment with few rhinaria and the hind basitarsus robust (Fig. 16).

Paralipsis planus van
Holotype, ♀, length of fore wing 2.0 mm, and of body 2.1 mm. Description. Head. Head 1.6 times wider than long medially in dorsal view and roundly narrowed behind eyes; antenna with 15 (left) or 16 (right) segments and 0.9 times as long as body, segments long erect setae (Figs 17, 20), third segment dull and 1.1 times as long as fourth segment, third-fourth segments without rhinaria and widened apically and fifth segments with few rhinaria, third, fourth and penultimate (= 14 th ) segments 2.2, 1.8 and 1.4 times as long as wide, respectively; maxillary and labial palpi with 2 and 1 segments, respectively; length of maxillary palp 0.2 times height of head; distance between anterior tentorial pits 1.4 times distance between pit and eye; eye with rather long setae; face mainly smooth, convex ventrally and laterally rather sparsely setose, with setae directed downwards; clypeus distinctly convex and smooth, with few erect setae; frons nearly flat (except superficial impression in front of anterior ocellus), without median groove, shiny, punctulate and rather densely setose; vertex with sparse short pubescence between sparse long setae and temple roundly narrowed posteriorly and shiny; eye 0.9 times as long as temple in dorsal view; OOL:diameter of posterior ocellus:POL = 12:3:11; stemmaticum distinctly wider posteriorly than laterally; length of malar space 1.7 times basal width of mandible, malar depression absent.
Mesosoma. Length of mesosoma 1.3 times as long as high; pronotal side smooth and largely glabrous, with deep oblique groove and anteriorly short; mesopleuron mainly smooth, shiny, punctulate but superficially rugulose anteriorly and medially convex; pleural sulcus distinctly crenulate; metapleuron mainly rugose; mesoscutum with some micro-sculpture, posteriorly shiny and with dense short pubescence between long setae, but sparsely so posteriorly, antero-medially slightly depressed and with few striae; notauli absent on disc; scutellar sulcus very deep; scutellum strongly convex but slightly depressed antero-medially, posteriorly distinctly above level of mesoscutum, largely rugulose and with long setae; dorsal face of propodeum smooth and shiny, posterior face subvertical and indistinctly rugulose, without areolation and laterally with short setae.
Legs. Hind coxa mainly smooth, punctulate and setose; tarsal claws medium-sized and very slender; fore tarsal segments slender (second-fourth segments distinctly longer than wide in dorsal view), with long setae and with long apical bristles, but fore basitarsus rather robust; length of femur, tibia and basitarsus of hind leg 3.4, 6.1 and 4.8 times as long as wide, respectively; hind basitarsus robust (Fig. 16); hind femur subbasally and hind tibia medially widened (Fig. 16), both with erect setae; inner hind tibial spur 0.2 times as long as hind basitarsus.
Metasoma. First tergite smooth, flattened and shiny, its maximum width at level of spiracles of ♀ 0.7 times distance between spiracle and apex of tergite (Fig. 19), parallel-sided posteriorly, tergite 1.1 times long as wide apically; second tergite smooth and glabrous except some setae, third and following tergites smooth and only with a subapical row of long setae; length of visible (and sparsely setose) part of elliptical ovipositor sheath 0.05 times fore wing.
Holotype, ♀, length of body 2.2 mm and of damaged fore wing 1.1 mm. Description. Head. Head 1.4 times wider than long medially in dorsal view and roundly narrowed behind eyes; antenna with 15 segments and as long as body, segments adpressed setose and setae rather short, third segment dull and 1.3 times as long as fourth segment, third-fifth segments without rhinaria and widened apically, third, fourth and penultimate segments 2.2, 1.8 and 1.4 times as long as wide, respectively; maxillary and labial palp with 2 and 1 segments, respectively; length of maxillary palp 0.2 times height of head; distance between anterior tentorial pits 1.2 times distance between pit and eye (Fig. 22); eye with long setae; face mainly smooth, convex ventrally and laterally rather densely moderately setose, with setae directed downwards; clypeus distinctly convex and smooth, with long erect setae (Fig. 21); frons convex, with shallow median groove, rather dull, punctulate and densely setose; vertex with dense short pubescence between sparse long setae and temple roundly narrowed posteriorly and with satin sheen; eye 0.9 times as long as temple in dorsal view; OOL: diameter of posterior ocellus: POL = 3:1:3; stemmaticum distinctly wider posteriorly than laterally (Fig. 26); length of malar space 1.9 times basal width of mandible, malar depression absent.
Legs. Hind coxa mainly smooth, punctulate and setose; tarsal claws medium-sized and very slender; fore tarsal segments slender (second-fourth segments distinctly longer than wide in dorsal view), with rather short setae and with long apical bristles (Fig.  21); length of femur, tibia and basitarsus of hind leg 3.6, 6.8 and 5.4 times as long as wide, respectively; hind femur subbasally and hind tibia medially widened (Fig. 24), both with erect setae; inner hind tibial spur 0.2 times as long as hind basitarsus.
Metasoma. First tergite smooth, rather convex and moderately shiny, its maximum width at level of spiracles of ♀ 0.9 times distance between spiracle and apex of tergite (Fig. 27), weakly diverging posteriorly, tergite 1.3 times as long as wide apically; second tergite smooth and setose, third and following tergites smooth and only with a subapical row of setae; length of visible (and sparsely setose) part of elliptical ovipositor sheath 0.05 times fore wing in paratype with complete wings.
Variation. Antenna of ♀ with 15 (3) segments; length of complete fore wing 1.8 mm and of body 2.2 mm; first tergite 1.3-1.5 times as long as wide apically; femora and tibiae brown or largely dark brown.