69 Polyplax guatemalensis sp. n. (Phthiraptera: Anoplura), a new sucking louse from Peromyscus grandis, a montane cloud forest rodent from Guatemala Lance A. Durden 1 and Ralph P. Eckerlin 2 1 Institute of Arthropodology and Parasitology, Georgia Southern University, P.O. Box 8056, Statesboro, Georgia 30460, USA; 2 Natural Sciences Division, Northern Virginia Community College – Annandale Campus, 8333 Little River Turnpike, Annandale, Virginia 22003, USA Key words: Phthiraptera, Anoplura, sucking louse, new species, Guatemala, Polyplax guatemalensis, Peromyscus grandis Abstract. The adult male and female of Polyplax guatemalensis sp. n. are described from the sigmodontine murid rodent Peromyscus grandis Goodwin collected in the Reserva de Biosfera, Sierra de las Minas, Guatemala, at an elevation of 2,200 m. The new species extends the number of known native species of Polyplax in the New World to four with none of them recorded south of Panama. Polyplax guatemalensis is morphologically most closely related to Polyplax auricularis which parasitises a cluster of closely related New World sigmodontine rodents from Canada to Panama. These two species can be distinguished from all other known species of Polyplax by the presence of partially overlapping, subtriangular, anterior abdominal plates in both sexes. Polyplax guatemalensis can be separated from P. auricularis by the abundant tergal abdominal setae and longer pseudopenis in males, and by the presence of one fewer anterior abdominal, subtriangular tergite and sternite in females. The sucking louse genus Polyplax Enderlein, 1904 is well represented in the Old World where 76 native species have been recorded (Durden and Musser 1994, Chin 1995) but poorly represented in the New World where, until now, just three native species have been recorded (Durden and Webb 1999). In addition to the three native New World species, Polyplax serrata (Burmeister, 1839) and Polyplax spinulosa (Burmeister, 1839) have accompanied introduced commensal mice and rats, respectively, and are now widespread in this region as they are throughout much of the world. Recently, one of us (RPE) was part of a field team that collected and inventoried small mammals and their ectoparasites in Guatemala. During this survey, a new species of Polyplax was collected from an endemic Central American sigmodontine murid rodent. The new louse is described and illustrated in this paper. MATERIALS AND METHODS The descriptive format followed in this paper is that of Durden and Webb (1999) which was based on that of Kim and Ludwig (1978). Names and abbreviations for setae follow those two papers and are spelled out in full when first mentioned in this paper. All louse specimens were cleared in 10% potassium hydroxide, dehydrated through a series of ethanol washes of ascending concentration, further cleared in xylene, and then slide-mounted in Canada balsam following standard procedures (Kim et al. 1986). Specimens were measured with a calibrated eyepiece graticule fitted into a high-power Olympus BH-2 light microscope. Drawings were prepared with the aid of a Leitz PRADO 500 microprojector. RESULTS Family P o l y p l a c i d a e Fahrenholz, 1912 Polyplax guatemalensis sp. n. Figs. 1-8 Male Figs. 1-4 (35 specimens): Length of holotype 1.325 mm; range 1.300-1.525 mm; mean 1.396 mm. Head, thorax and abdomen moderately sclerotised. Head slightly longer than wide, relatively blunt anteriorly with anterolateral lobe on each side; 1 dorsal anterior head seta (DAnHS), 2 dorsal preantennal head setae (DPaHS), 1 supraantennal head seta (SpAtHS), 1 sutural head seta (SuHS), 1 dorsal marginal head seta (DMHS), 1 dorsal posterior central head seta (DPoCHS), 1 relatively long dorsal principal head seta (DPHS), 1 short dorsal accessory head seta (DAcHS), 1 apical head seta (ApHS), 2 anterior marginal head setae (AnMHS), 2 ventral preantennal head setae (VPaHS) and 1 stout ventral principal head seta (VPHS) on each side. Antennae 5-segmented with basal segment much larger than other segments, slightly wider than long; third antennal segment modified with anterodorsal projection. Thorax longer than broad with margins tapering an- teriorly; thoracic sternal plate (Fig. 2) shield-shaped but with concave edges especially apparent anteriorly and posteriorly; mesothoracic spiracle diameter 0.024 mm; dorsal principal thoracic setae (DPTS) moderate in length (0.14 mm); no other thoracic setae present except on legs. Legs with subtriangular coxae; forelegs small with narrow acuminate claw; mid- and hindlegs progressively larger each with correspondingly larger acuminate claw. FOLIA PARASITOLOGICA 48: 69-72, 2001 Address for correspondence: L.A. Durden, Institute of Arthropodology and Parasitology, Georgia Southern University, P.O. Box 8056, Statesboro, Georgia 30460, USA. Phone: ++1 912 681 0553; Fax: ++1 912 681 0559; E-mail: ldurden@gsvms2.cc.gasou.edu