Calidolipeurus, new genus for Lipeurus megalops Piaget, 1880 (Phthiraptera: Ischnocera: Oxylipeurus-complex), with a redescription of the type species and a preliminary key to the Oxylipeurus-complex

The chewing louse species Lipeurus megalops Piaget, 1880, is redescribed and illustrated. This species has previously been placed in the genus Oxylipeurus Mjöberg, 1910, but marked differences in preantennal structure, male and female genitalia, abdominal chaetotaxy, and structure of abdominal plates indicate that this species is not closely related to other species in this genus. We therefore erect a new genus, Calidolipeurus gen. nov. for this species. Calidolipeurus is presently monotypic, containing only Calidolipeurus megalops gen. et comb. nov. We also provide a preliminary key to the Oxylipeuruscomplex.


Introduction
The first comprehensive review of the Oxylipeurus-complex was by Clay (1938), who considered all species to belong to the same, morphologically variable, genus, Oxylipeurus Mjöberg, 1910. Within this genus, she designated six species groups, based on rough similarities in morphology. The third group comprised four species parasitizing small-bodied partridges in Southeast Asia, including However, in recent decades, redescriptions of several species in the Oxylipeurus-complex have been published (Mey 1990(Mey , 2010, including that of the type species Oxylipeurus inaequalis (Piaget, 1880). These indicate that Oxylipeurus s. str. is morphologically very different from most other species in the Oxylipeurus-complex, and that several genera commonly synonymized with Oxylipeurus (e.g., Price et al. 2003) should be accepted as valid. Mey (2009Mey ( , 2010 has recently considered the genus Megalipeurus as a valid genus, including the species L. megalops. We agree that all of the genera considered synonyms of Oxylipeurus in the recent checklist of Price et al. (2003) should be accepted as valid, following Mey (2009Mey ( , 2010 and Gustafsson et al. (2020). This includes the recognition of the following genera considered synonymous with Oxylipeurus in the checklist of Price et al. (2003): Eiconolipeurus Carriker, 1945, Epicolinus Carriker, 1945, Megalipeurus Kéler, 1958, Reticulipeurus Kéler, 1958and Talegallipeurus Mey, 1982 However, Mey (2009) includes the species L. megalops in Megalipeurus, following its placement in Group III by Clay (1938) and in Megalipeurus by Kéler (1958). Oxylipeurus megalops is similar to other species in Megalipeurus in the presence of elongated and strongly sclerotized coni and in the general shape of the female subgenital plate, but it differs from all other species in the Oxylipeurus-complex in many significant characters (see below). We therefore here propose a new genus, Calidolipeurus gen. nov. for L. megalops.

Material and methods
All examined specimens are deposited at the Natural History Museum, London, United Kingdom (NHMUK). Drawings were made using a drawing tube attached to a Nikon Eclipse Ni (Nikon Corporation, Tokyo, Japan) and edited in GIMP (www.gimp.org). Measurements (all in mm) were made from live images in NIS-Elements (Nikon Corporation, Tokyo, Japan) for the following dimensions: HL = head length (along midline); HW = head width (at temples); POW = preocular width (at preantennal nodi); PRW = prothoracic width; PTW = pterothoracic width; AW = abdominal width (at segment V); TL = total length (along midline, including stylus). Terminology of morphological and setal characters and abbreviations thereof follow Gustafsson & Bush (2017).
Calidolipeurus can be separated from Megalipeurus by the following characters: marginal carina interrupted only near as1 in Megalipeurus, but interrupted near as1 and as2 in Calidolipeurus  (Fig. 5), but not in Megalipeurus; eyes gigantic in Calidolipeurus (Fig. 5), but not in Megalipeurus; preocular nodus present in Megalipeurus but absent in Calidolipeurus (Fig. 5); stylus reaches beyond distal margin of abdomen in Calidolipeurus (Fig. 3), but not in Megalipeurus; ss present on male abdominal segments VI-VII in Megalipeurus, but absent in Calidolipeurus (Fig. 1); psps present and of equal size on male tergopleurites IV-VI in Megalipeurus, but present on tergopleurites IV-VII in Calidolipeurus ( Fig. 1) with those of tergopleurites VI-VII microsetae; male subgenital plate with lateral extensions following genital opening in Calidolipeurus (Fig. 3), but without such extensions in Megalipeurus; parameres very broad proximally, with overall shape roughly triangular in Calidolipeurus (Fig. 12), but with slender heads in Megalipeurus; proximal mesosome with large rounded lobes on each side in Megalipeurus, but without such lobes in Calidolipeurus (Fig. 9); gonopore with lateral hook-shaped elongations in Calidolipeurus (Fig. 11), but roughly rounded in Megalipeurus.

Etymology
Calidolipeurus is constructed from the Latin 'calidus' for 'white spot in the forehead' and the genus name Lipeurus Nitzsch, 1818, commonly used for long and slender ischnocerans. This refers to the small, elongated dorsal preantennal suture of the type species, which appears white in many specimens in contrast to the otherwise brownish head. Gender: masculine. Thoracic and abdominal segments as in Figs 1-2. Legs as in ; similar between sexes but some setae more slender in female than in male. Meso-and metasterna fused. Metepisterna long, with extensive striation. Tergopleurites II-VII medianly separated; tergopleurite VIII medianly continuous in posterior end; tergopleurites IX + X and XI fused. Sternites medianly continuous, reticulated in both sexes. Subgenital plates differ between sexes, formed by fusion of sternites VIII-IX.

Male
Pedicel and flagellomere I with rugose antero-dorsal surface; flagellomere with antero-dorsal claw-like elongation. Thoracic and abdominal chaetotaxy as in Fig. 1; ss present on segments II-V; psps present on segments IV-VII, those of VI-VII microsetae. Tergopleurite IX-XI with variable lateral incision reaching apertures of setae. Subgenital plate with extensive reticulation (Fig. 3), distally elongated into protruding stylus; lateral extensions on each side of base of stylus associated with anterior margin of ventral genital opening. Basal apodeme elongated, of roughly equal width, but in some specimens with concave lateral margins (Fig. 8). Mesosome largely unsclerotized, and looks different in specimens with everted or non-everted genitalia. Proximal mesosome flattened to concave, but diffuse and here illustrated approximately (Figs 8-11); on each side sinusoid thickening articulating with parameral heads. Distal mesosome roughly quadratic, with extensive folds and serrations on dorsal and ventral surfaces. Internal sclerite roughly heart-shaped (Fig. 10). Gonopore longer than wide, with lateral hook-shaped in distal end; in anterior end a dark central sclerite may be proximal part of endophallus; one small aperture on each side of presumed endophallus may be microsetae, but setae not visible in examined specimens. In everted genitalia, the gonopore extends beyond distal margin of mesosome, and rugose areas of mesosome contracted (Figs 8-9). Parameres roughly triangular (Fig. 12), median corners of heads almost touching anteriorly; median margin of anterior parameres weakly sclerotized; pst1 not visible; pst2 microsetae near distal end of paramere.

Female
Pedicel and flagellomere I without rugose areas and without claw-like elongation. Head chaetotaxy similar to male, but s7 shorter. Thoracic and abdominal chaetotaxy as in Fig. 2; ss present on segments II-V; psps present on segments IV-VII; those on VI-VII microsetae. No lateral incision of tergopleurite IX-XI in examined specimens. Subgenital plate formed by fused sternites VIII-IX (Fig. 4); proximal margin deeply indented medianly. Vulval margin strongly convex; setae situated anterior to margin and do not form distinct sets. Subvulval sclerites absent. Lateral and posterior margins of abdominal segment IX-XI with more or less equally spaced and equal-sized setae.

Female
Proximal margin of subgenital plate typically with two setae on each side, but placement asymmetrical and 1-3 setae may be present on each side; lateral setae about twice as long as median setae. Vulval margin with 10-15 slender setae on each side (Fig. 4)

Remarks
Piaget (1880) gives as type locality Madagascar, which is well outside the range of the host species (Madge & McGowan 2002). Clay (1938) examined Piaget's types, which she found to be identical to material from Borneo. Piaget's type locality designation is therefore here considered erroneous.
We have seen photos of the lectotype and paralectotype (at NHMUK), but not examined these specimens in person. The photo of the female lectotype does not differ from the non-type specimens we have examined.

Preliminary key to the genera of the Oxylipeurus-complex
Characters taken primarily from Clay (1938), Clay & Meinertzhagen (1941), Carriker (1945Carriker ( , 1967, Emerson & Ward (1958), Kéler (1958), Elbel & Price (1970), Mey (1982Mey ( , 1990Mey ( , 2006Mey ( , 2010, Gustafsson et al. (2020), and examinations of specimens. Additional groups deserving recognition at the genus level may exist, and many species of the complex are in need of further study and redescription. The genus Labicotes Kéler, 1939, may also belong to this complex, based on similarities in male and female terminalia, male genitalia, and temporal chaetotaxy between this genus and Chelopistes. This needs to be confirmed by additional studies of species of Labicotes, and the genus is not included here.