Peripsocus stagnivagus Chapman, 1930

Lienhard, Charles & Mifsud, David, 2015, Psocids from Malta (Insecta: Psocodea: ‘ Psocoptera’), with new synonymy for Peripsocus stagnivagus based on the discovery of its first Palaearctic male, Zootaxa 3936 (2), pp. 251-260 : 256

Peripsocus stagnivagus Chapman, 1930

Peripsocus bivari Baz, 1988: 6 . syn. nov.

Peripsocus leleupi Badonnel, 1976: 218 . syn. nov.

Material examined. Malta, Verdala Palace, 12–24. vi.2014, 2 ♀, Malaise trap, DM; same data but 25.vi.–10. vii.2014, 3 ♀; 11.vii.–1.viii.2014, 37 ♀; 1–15. viii.2014, 6 ♀; 15–30. viii.2014, 1 ♂ and 246 ♀; and 1–30.ix.2014, 298 ♀.

Notes. A new record for the Maltese Islands. The Maltese population of this species apparently reproduces by thelytokous parthenogenesis, as do most Nearctic populations of P. stagnivagus ( Mockford 1971) . By chance, one male was found among the almost 600 females collected from Malta, as occasionally happens in obligatorily thelytokous psocids (see Lienhard 1998: 45). No morphological differences were found between the Maltese male and the Nearctic male of P. stagnivagus ; the latter was well described and illustrated by Mockford (1993). Lienhard (1998: 262) stated that the females of P. b i v a r i, described by Baz (1988) and redescribed by Lienhard (1998), and P. leleupi , described by Badonnel (1976), cannot be distinguished either from each other or from the North American P. stagnivagus ; the female of the latter was described by Chapman (1930) and redescribed by Mockford (1993). Based on the discovery of the first Palaearctic male of P. stagnivagus , the synonymy of these names is here formally proposed.

Peripsocus stagnivagus in the narrow sense is a predominantly Nearctic species considered by Mockford (2012) as a native element of deciduous forests in the eastern United States. However, it has been recorded also from Central America ( Cuba, Mexico, Panama), the Galapagos Islands and from Bermuda (see Lienhard & Smithers 2002). According to Mockford (1993: 215), some of the Mexican populations represent two undescribed species: “the three [species] are readily separated on male characters, but females appear to be indistinguishable morphologically” (Mockford loc. cit.). Following the proposed synonymy, the distributional range of P. stagnivagus is widened to include Macaronesia (Azores, Canary Islands, and Madeira), western North Africa ( Morocco) and western France (i.e. range of P. b i v a r i, see Lienhard 1998 and Lienhard & Smithers 2002), and also the South Atlantic islands of St. Helena and Ascension (i.e. range of P. leleupi , see Badonnel 1976 and Lienhard & Ashmole 2011). The easternmost Palaearctic record is the present one from Malta.

Among the European psocids, P. b i v a r i has been considered as an alien element of unknown origin by Schneider (2010). In fact, the distribution range of P. stagnivagus resulting from the proposed synonymy suggests an introduction of this psocid from the Nearctic. The high potential for dispersal of this species is probably largely due to its predominantly parthenogenetic reproduction. Another example of an extremely widespread parthenogenetic psocid is Trichadenotecnum cicularoides Badonnel (thelytoky demonstrated by Mockford 1974), which has been recorded from all zoogeographical regions (see Lienhard & Smithers 2002 and Yoshizawa & Smithers 2006).

Peripsocus stagnivagus is the smallest of the European Peripsocus species (body length of females 1.6–1.8 mm, of the Maltese male 1.4 mm; forewing length of females 1.5–1.7 mm, of the Maltese male 1.6 mm). The compound eyes are distinctly larger in the male (IO/D = 1.25) than in the females (IO/D about 2.4). This sexual dimorphism was crucial for rapid detection of the single male among the almost 250 females collected in a single Malaise trap sample. The colouration of the forewing is variable; its membrane is faintly tinged with brown and usually some darker patches are clearly visible, especially in cells r5 to m3 (see Baz 1988: fig. 9; Lienhard 1998: fig. 84d); but these patches are often weakly developed or even absent, as is the case in the male and in many females from Malta. In the identification key proposed by Lienhard (1998), the male of P. stagnivagus keys out with P. parvulus . However, the latter is much larger (male forewing length 2.1–2.3 mm). The phallosome of P. parvulus is somewhat similar in shape to that of P. stagnivagus and has also a pair of anteromedially curved appendages arising at the base of the aedeagal arch (see Lienhard 1998: fig. 83q). However, the males of these species are easy to distinguish by the characteristic shape of the endophallic sclerites (compare Fig. 1 A with Lienhard 1998: fig. 83p). The clunial comb is similar in both species, with about a dozen of well-developed rounded teeth in P. stagnivagus ( Fig. 1 B) and a somewhat higher number of such teeth in P. parvulus (see Lienhard 1998: fig. 83t). The male of P. stagnivagus is clearly not identical with the holotype of the enigmatic P. yuleki Galil, 1983 described from Israel ( Galil & Halperin 1983); the latter remains a “species inquirenda” (see discussion in Lienhard 1998: 256).

Figures

FIGURE 1. Peripsocus stagnivagus Chapman. Male from Malta: A, Phallosome, dorsal view. B, Clunial comb, dorsal view. Scale (A, B) 0.1 mm.