New species of Philopterus Nitzsch , 1818 ( Ischnocera : Philopteridae ) , with notes on Cypseloecus Conci , 1941

We describe and illustrate eight new species of chewing lice in the genus Philopterus Nitzsch, 1818, parasitic on hosts in the bird families Cardinalidae, Chloropseidae, Hirundinidae, Icteridae, Motacillidae, Paridae, and Vangidae from China, Peru, South Africa, Thailand, and the USA. They are: Philopterus coriaceus sp. nov. from Molothrus oryzivorus oryzivorus (Gmelin, 1788); P. hebes sp. nov. from Chloropsis aurifrons inornata Kloss, 1918 and C. cochinchinensis kinneari Hall & Deignan, 1956; P. micropunctatus sp. nov. from Anthus hodgsoni Richmond, 1907; P. afropari sp. nov. from Melaniparus cinerascens cinerascens (Vieillot, 1818); P. pseudhirundo sp. nov. from Pseudhirundo griseopyga Sundevall, 1850; P. sinensis sp. nov. from Hemipus picatus capitalis (Horsfi eld, 1840); P. stansburyensis sp. nov. from Pheucticus melanocephalus melanocephalus (Swainson, 1827); and P. trepostephanus sp. nov. from Tephrodornis virgatus fretensis Robinson & Kloss, 1920 and T. v. mekongensis Meyer de Schauensee, 1946. Philopterus hebes sp. nov. constitutes the fi rst record of the genus Philopterus from the Chloropseidae. We also provide some notes on the morphology and status of Cypseloecus Conci, 1941.

Comparatively little work has been done to elucidate the relationships of lice within the genus Philopterus. In the most comprehensive treatment thus far, Złotorzycka (1964) and Złotorzycka & Lucińska (1975, 1976 separated groups based largely on host associations; they considered the genus Philopterus to be limited to the species parasitizing corvid hosts (Corvidae), and the genus Cypseloecus Conci, 1941 was limited to species parasitizing swallows (Hirundinidae). All other species were placed in the genus Docophorulus Eichler, 1944. Złotorzycka & Lucińska (1975, 1976 further divided both Philopterus and Docophorulus into species groups; however, these treatments only considered European species, and thus do not cover the vast majority of the diversity of this near-global group. Moreover, the morphological characters that underpin the Złotorzycka-Lucińska (1975, 1976 classifi cation are often of dubious usefulness, which is exacerbated by the fact that few other detailed descriptions and illustrations of these species have been published. In most cases, comparisons with type specimens are necessary for identifi cation of the species included in this classifi cation system. Hopkins & Clay (1952) and Price et al. (2003) considered most proposed genera in this group to be synonymous with Philopterus. However, Mey (2004) resurrected several genera based on morphological arguments, and described several new genera in the complex. Moreover, recent genetic data suggest that the genus Philopterus, as currently circumscribed, is paraphyletic (Najer et al. 2020b), with the genera Tyranniphilopterus Mey, 2004 andPhilopteroides Mey, 2004 possibly nested inside Philopterus.
A thorough revision of the Philopterus complex based on morphological and genetic data is sorely needed. Such an undertaking is beyond the scope of this study; however, we identify, describe and illustrate several morphological characters that are likely to prove useful in understanding relationships among taxa in the complex. For example, the structure of the mesosome is highly variable between species, suggesting that male genital characters may be useful for fi nding and delimiting species groups within the genus. In contrast, most somatic and setal characters of the species in Philopterus are quite conserved, which may indicate evolutionary relationships among more distantly related species (see below).
Here we describe eight new species of Philopterus belonging to diff erent groups within this genus. For all species, we have made a special eff ort to describe and illustrate key morphological characteristics to facilitate identifi cation, and to lay a solid taxonomic foundation that can be used in the future formation of species groups within the genus Philopterus. We do not propose any new species groups here, but we note that the species parasitizing swallows are morphologically distinct and the genus Cypseloecus should be resurrected, either as a subgenus of Philopterus or as a separate genus.

Material and methods
Slide-mounted specimens were examined with Nikon Eclipse E600 and Nikon Eclipse TI-E light microscopes (Nikon, Tokyo, Japan). Illustrations were made through the same microscopes, fi tted with a drawing tube or Andor Clara camera (Oxon, United Kingdom), then collated and edited in GIMP (www.gimp.org) and NIS Elements 4.50.00 LO (Nikon, Tokyo, Japan) using an Intuos 3 PTZ-1230 tablet (Wacom, China). Measurements were made from photos taken with the same microscope with GUSTAFSSON D.R. et al., New Philopterus with notes on Cypseloecus 3 an Olympus DP25 camera and digital measuring software (ImageJ ver. 1.48, Wayne Rasband). All measurements are given in millimetres, as ranges (mean value, when n ≥ 10). Dimensions taken and abbreviations thereof follow Najer et al. (2016), and include: ADPL = dorsal anterior plate length (at midline) ADPW = dorsal anterior plate width AL = abdominal length (at midline) ANW = anterior notch width APLL = dorsal anterior plate lateral length AW = abdominal width (at segment V) GL = genital length (in male) GW = genital width (in male) HL = head length (at midline, including hyaline margin) HW = head width (at temples) PAL = preantennal length PAW = preantennal width (at base of coni) PMCL = premarginal carina length POL = postantennal length (at midline) PRL = prothoracic length PRW = prothoracic width PTL = pterothoracic length (at midline) PTW = pterothoracic width SGPW = subgenital plate width (in female) TL = total length (at midline, including hyaline margin) TPVL = tergal plate V length TRL = trabeculum length TRW = trabeculum width Morphological and setal terms and their abbreviations follow Clay (1951), Mey (1994), Najer et al. (2016), and Gustafsson & Bush (2017). Names for setal characters are given in italics, whereas abbreviations for structural characters are given in upper-case. Tergal, pleural, and sternal setae were counted on each side separately, and counts given here denote setae on one side only; these normally diff er between the sides of the same specimen as well as between specimens. Note that the trichobothria and thorn-like setae of the pterothorax and trichobothria of abdominal segment VIII of both sexes are not included in the setal counts, as these are constant throughout the Philopterus complex. For clarity, some pleural setae were illustrated on the dorsal side; however, as the lateral margins of the abdomen are typically non-sclerotized, the exact location of these setae depends on the position of the mounted specimen. In some cases, single pleural setae are situated on the postero-lateral corner of the tergopleurite or in an unsclerotized invagination of this corner. Abbreviations for setal characters follow Gustafsson & Bush (2017) and include: ads = anterior dorsal seta as1-3 = anterior setae 1-3 avs1-3 = anterior ventral setae 1-3 dsms = dorsal submarginal seta mds = mandibular seta mts1-5 = marginal temporal setae 1-5 os = ocular seta pas = preantennal seta pcs = preconal seta pos = preocular seta  Conci, 1941: 126. Debeauxoecus Conci, 1941: 126. Docophorulus Eichler, 1944: 80. Bitrabeculus Uchida, 1948: 317. Prunellides Złotorzycka & Eichler, 1984: 219, fi gs 1-3.

Geographical distribution
As currently circumscribed (Mey 2004), likely global apart from Antarctica, but poorly known in the Southern Hemisphere.

Host associations
As currently circumscribed (Mey 2004), widely distributed across hosts in the Passeriformes. A single species (Philopterus solus Tendeiro, 1962) has been described from a bucerotiform host, but Mey (2004: 200) doubted the authenticity of this record.

Remarks
All species described herein key to the genus Philopterus in the key of Mey (2004), based on having both trabecula and coni, an extensive hyaline margin, dorsal anterior plates that are longer than wide, and ventral carinae that are not recurved towards the preantennal nodi. However, other characters are quite variable among the species described here, and ascertaining homologous structures can be diffi cult, especially in the male genitalia. Moreover, one distinguishing character of Philopterus in Mey's key is the similarity in the length of the os, pos, and mts1-3; yet, the relative lengths of these setae vary in the species treated here. The number and position of sensilla of the postantennal head also vary between species. Most likely, this variation corresponds to deep divisions between diff erent groups of Philopterus sensu Mey (2004), some of which may ultimately be considered diff erent genera or subgenera.
Many species of Philopterus are inadequately described, with much of the description being based on measurements, and most of the illustrations being of characters of limited taxonomic value (prosternal plates, shape of trabecula, single tergopleurites with only some of the setae illustrated). Finding suitable species to compare potential new species with is, therefore, often diffi cult. Here, we primarily compare our new species with other species from the same, or a closely related host family. In cases where known species of Philopterus on the same host family are clearly very diff erent (e.g., Philopterus afropari sp. nov.), or where no species of Philopterus were described from the same host family, we expanded our comparison to species from other host families, principally ones in the same geographical region. In some cases (e.g., Philopterus hebes sp. nov.), no closely related species of Philopterus were identifi able.
We also referred to the species groups proposed by Złotorzycka & Lucińska (1976); however, these species group are of limited use as they only include Central European species of Philopterus. Moreover, the morphological characters on which these species groups are based are sometimes hard to interpret, diff er somewhat between species groups, and are of limited or unknown phylogenetic utility. Finally, all illustrations and descriptions in Złotorzycka's publications (e.g., Złotorzycka & Lucińska 1976) are partial and poor, and not all species are illustrated. Nevertheless, the partial revisions of Philopterus in Złotorzycka & Lucińska (1976) and Złotorzycka (1964) are the only published attempts to structure the species in Philopterus.

Diagnosis
It is diffi cult to ascertain which species of Philopterus is most similar to P. hebes sp. nov. The broad and relatively short preantennal head of P. hebes sp. nov. is reminiscent of that of P. chilchil Ansari, 1955[ex Turdoides caudata caudata (Dumont, 1823; see Ansari (1958) for an illustration; type specimens of P. chilchil are presumed lost (Naz et al. 2020)]. Both P. hebes sp. nov. and P. chilchil have very broad dorsal anterior plates with broad posterior extensions. However, the illustrations of P. chilchil published by Ansari (1958) are inadequate to compare the two species properly; for instance, the subgenital plate and many head setae are absent in Ansari's illustration and not described in detail in the text. The male genitalia of P. chilchil are poorly illustrated and not described. From what can be seen in Ansari's illustrations, P. hebes sp. nov. can be separated from P. chilchil by the following characters: distal mesosome broadly triangular with pointed distal end in P. chilchil, but rounded with concave lateral margins in P. hebes sp. nov. ; proximal mesosome extensive, with concave lateral margins and convex proximal margin in P. chilchil, but simple, with convergent convex lateral margins in P. hebes sp. nov. (Fig. 5); hyaline margin apparently very narrow and weakly concave in P. chilchil, but extensive, with moderate concavity in median section in P. hebes sp. nov. (Figs 1-3). Closer comparison of the genitalia of both sexes and chaetotaxy will have to await the redescription of P. chilchil.

Description
Head shape and chaetotaxy as in Fig. 3, preantennal area very broad. Hyaline margin wide, not extending much lateral to marginal carina, concave medianly. Dorsal anterior plate roughly pentagonal, anterior margin shallowly concave, lateral corners rounded. Ventral anterior plate wide, shallowly crescentshaped. Posterior margin of dorsal preantennal suture unclear in examined specimens. Coni slender, curved posteriorly. Gular plate small. Thoracic and abdominal segments as in Figs 1-2. Measurements as in Table 1.

Female
Thoracic and abdominal chaetotaxy as in Fig. 2 and Tables 2-4. Central sternal plates absent, lateral accessory plates not clearly visible. Subgenital plate and vulval margin as in Fig. 6; chaetotaxy as in Fig. 6 and Table 3. Subvulval plates with notch on lateral margin.

Etymology
The species name is derived from the Greek 'mikro' for 'small' and the Latin 'punctatus' for 'dotted', referring to the many small dots median to the subvulval plates. Table 3. Abdominal and vulval chaetotaxy of the species of Philopterus Nitzsch, 1818 described in this paper. Only sternal setae are listed here; for tergal setae, see Table 2; for pleural setae, see Table 4. Numbers denote the numbers of setae on one side of the abdomen only; for setal counts in the entire setal row of each segment, these numbers thus need to be doubled.  Philopterus hebes sp. nov.

Description
Head shape and chaetotaxy as in Fig. 9, preantennal area moderately broad. Hyaline margin wide, slightly concave medianly, not extending much lateral to marginal carina. Dorsal preantennal plate long, narrowing gently posteriorly, with distinct lateral thickenings along much of lateral margins anterior to ads. Ventral anterior plate bluntly crescent-shaped. Coni small, pointed posteriorly. Thoracic and abdominal segments as in Figs 7-8. Measurements as in Table 1. Table 4. Abdominal chaetotaxy of the species of Philopterus Nitzsch, 1818 described in this paper. Only pleural setae are listed here; for tergal setae, see Table 2; for sternal setae, see Table 3. Numbers denote the numbers of setae on one side of the abdomen only; for setal counts in the entire setal row of each segment, these numbers thus need to be doubled. Abbreviations: ant. = anterior end; post. = posterior end.
1 Segments V-VI with additional, shorter sternal setae lateral to those associated with the sternal plate; on segment IV of single examined male these are closer to the pleural setae, and these setae are therefore here included in the count of pleural setae on all segments.

Louse
Sex Pleural

Female
Thoracic and abdominal chaetotaxy as in Fig. 8 and Tables 2-4. Central sternal plates absent on segments II-VI. Lateral accessory plates present on segments III-VI. Subgenital plate as in Fig. 12; lateral sclerotizations of vulval area extended posteriorly to approach vulval margin; in one female also extended anteriorly to fuse with subgenital plate. Vulval margin more or less straight, chaetotaxy as in Fig. 12 and Table 3. Subvulval plates slender distally, with many small fragmentary dots between plates as in Fig. 12.
Philopterus afropari sp. nov. urn:lsid:zoobank.org:act:6737F5C9-8DE2-4074-9C6E-BD62F2E4E10D Figs 13-18; Tables 2-5 Diagnosis Philopterus afropari sp. nov. is not similar to any species of Philopterus known from Holarctic parid hosts, which are all characterized by having the dorsal anterior plate with pointed postero-lateral corners near ads on each side, 3-4 setae on each side on the posterior margin of the pronotum, and a long and narrow basal apodeme (Fedorenko & Vasjukova 1985;Mey 1988Mey , 1994. In contrast, P. afropari sp. nov. lacks the pointed corners of the dorsal anterior plate, has only one posterior seta on each side of the pronotum, and has a broader basal apodeme. No species of Philopterus has been described from other African parids. Philopterus afropari sp. nov. is somewhat similar to P. solus Tendeiro, 1962, another African species associated with a host in the Bucerotiformes (Rhinopomastus cyanomelas schalowi Neumann, 1900). These two species share the following characters: hyaline margin wide but relatively short; dorsal anterior plate broadly trapezoidal; coni small with concave anterior margins; male subgenital plate with at least 2 lateral lobes on each side and a lateral accessory sternal plate on abdominal segment IX+X (fused with subgenital plate in one specimen examined in Tendeiro 1962). Most notably, the gonopore of both species is of similar shape and the ventral section of the mesosome is largely indistinguishable from the distal basal apodeme in both species; dorsally, the mesosome of P. afropari sp. nov. (Fig. 16) appears to be similar to the dark section of the distal basal apodeme in Tendeiro's photo of P. solus, but this section is not clearly illustrated by Tendeiro (1962), and the photo is of poor quality.
These two species can be separated by the following characters: os and pos of more or less equal length in P. afropari sp. nov. (Fig. 15), but pos much longer than os in P. solus; preantennal head longer and more slender in P. afropari sp. nov. (Fig. 15) than in P. solus; central sternal plates evidently absent in males of P. solus, but present in males of P. afropari sp. nov. (Fig. 13); lateral lobes of male subgenital plate of roughly equal size in P. solus, but posterior lobe much larger than anterior lobe in P. afropari sp. nov. (Fig. 13); basal apodeme in P. solus with clear central thickenings presumably associated with the endophallus, but no such structures visible in P. afropari sp. nov. (Figs 16-17); central posterior extension of the female subgenital plate more prominent in P. afropari sp. nov. (Fig. 18) than in P. solus. Note that P. solus is in need of a more detailed redescription before a complete comparison between these two species can be made.

Description
Head shape and chaetotaxy as in Fig. 15, preantennal area broad. Hyaline margin wide, extending laterally beyond marginal carina, shallowly concave medianly. Dorsal anterior plate broad, trapezoidal, with broad, blunt posterior extension. Ventral anterior plate roughly triangular, with shallowly concave anterior margin. Coni small, distal end in some specimens curved slightly anteriorly. Gular plate small, irregular. Thoracic and abdominal segments as in Figs 13-14. Measurements as in Table 5.

Male
Thoracic and abdominal chaetotaxy as in Fig. 13 and Tables 2-4. Tergopleurite IX+X medianly continuous. Abdominal segments II-V with no central sternal plate, but with lateral accessory plates; segment VI with narrow, typically very fragmented central sternal plate and large lateral accessory plates. Subgenital plate with 3 lateral lobes on each side and small lateral accessory plate of segment IX+X. Basal apodeme broad (Figs 16-17), much constricted at mid-length. Mesosomal thickening large, with sinuous lateral margins and distal thickening (Fig. 16); 3 microsetae on each side of mesosome. Gonopore large (Fig. 17), widening distally. Parameres fused to basal apodeme, slender; pst1-2 as in Fig. 17.

Female
Thoracic and abdominal chaetotaxy as in Fig. 14 and Tables 2-4. Subgenital plate as in Fig. 18, with more weakly sclerotized sections on anterior and posterior ends. Vulval margin concave medianly (Fig. 18), chaetotaxy as in Fig. 18 and Table 3. Subvulval plate large, irregularly triangular, often with minute accessory plate laterally.

Etymology
The specifi c epithet is derived from the type locality.

Description
Head shape and chaetotaxy as in Fig. 21, preantennal area wide. Hyaline margin broad, not extending laterally beyond marginal carina, shallowly indented medianly. Dorsal anterior plate almost square, with broad, blunt posterior extension. Ventral anterior plate near-rectangular, wide and short, with slightly concave anterior margin. Coni small, curved slightly anteriorly. Gular plate small, irregular. Thoracic and abdominal segments as in Figs 19-20. Measurements as in Table 5.

Male
Thoracic and abdominal chaetotaxy as in Fig. 19 and Tables 2-4. Abdominal segment II without central sternal plate but with lateral accessory plates; segments III-V with small to wide central sternal plates and lateral accessory plate on each side; segment VI with wide central sternal plate fused to lateral accessory plates. Subgenital plate broad, lateral notches small, lateral sternal plate of segment IX+X fused to subgenital plate. Basal apodeme broad (Figs 22-23), constricted in distal half. Mesosomal thickening oblong, irregular; 3 microsetae on each side of mesosome. Gonopore with convergent anterior margin and bulbous distal extensions (Fig. 23), 2 sensilla on each side of gonopore. Parameres fused to basal apodeme, long, slender; pst1-2 as in Figs 22-23.

Female
Thoracic and abdominal chaetotaxy as in Fig. 20 and Tables 2-4. Central sternal plates absent, lateral accessory plates present on segments II-VI. Subgenital plate and vulval margin as in Fig. 24, chaetotaxy as in Fig. 24 and Table 3. Subvulval plates partially obscured by gut content, but appear to be broad, blunt distally.

Diagnosis
Apart from the similarity between Philopterus trepostephanus sp. nov. and P. sinensis sp. nov. outlined under the latter species (see above), P. trepostephanus sp. nov. does not appear to be morphologically close to any other known species of the genus. The species morphologically closest to P. trepostephanus sp. nov. may be P. petrescuae Adam in Sychra et al., 2011(ex Dicrurus hottentottus (Linnaeus, 1766). These two species share the following characters: hyaline margin extends lateral to as1 (Fig. 27); ventral sclerite of male mesosome with lateral extensions (Fig. 29); long vulval setae far anterior to the vulval margin (Fig. 30); gonopore extensive, collar-shaped. These two species can be separated by the following characters: lateral extensions of ventral mesosomal sclerite in distal half in P. trepostephanus sp. nov. (Fig. 29), but in proximal half in P. petrescuae, and the overall shape of this sclerite also diff ers between these species; coni with recurving anterior 'hooks' in P. petrescuae, but without such hooks in P. trepostephanus sp. nov. (Fig. 27); central sternite absent on male abdominal segment VI in P. petrescuae, but present in P. trepostephanus sp. nov. (Fig. 25); lateral lobes of hyaline margin more extensive in P. petrescuae than in P. trepostephanus sp. nov. (Fig. 27); dorsal anterior plate (ignoring posterior extension) longer than wide in P. petrescuae, but about as wide as long in P. trepostephanus sp. nov. (Fig. 27); macrosetae of female subgenital plate all situated on plate in P. trepostephanus sp. nov. (Fig. 30), but lateral setae on each side situated lateral to plate in P. petrescuae.

Etymology
The species name is constructed from 'trepo', Greek for 'I turn', and 'stephanos', Greek for 'crown, wreath'. This refers to the shape of the gonopore, with its anterio-lateral hooks. Paratypes THAILAND • 1 ♀; same collection data as for holotype; NHMUK • 1 ♂; same collection data as for holotype; PIPR.

Description
Head shape and chaetotaxy as in Fig. 27, preantennal area broad. Hyaline margin broad, extending laterally beyond marginal carina, shallowly concave medianly. Dorsal anterior plate roughly quadratic, with shallowly concave anterior margin and broad posterior extension. Ventral anterior plate roughly semicircular, with slightly concave anterior margin. Coni moderate, slender, pointed posteriorly. Gular plate large. Thoracic and abdominal segments as in Figs 25-26. Measurements as in Table 5.

Male
Thoracic and abdominal chaetotaxy as in Fig. 25 and Tables 2-4. Central sternal plates absent on segments II-V, present and broad on segment VI. Lateral accessory plates present on segments II-VI. Subgenital plate broad anteriorly, narrowing markedly on segment IX+X, widening distally; lateral accessory plates present on abdominal segment IX+X, of about same size as other lateral accessory plates. Basal apodeme short, slender, constricted at mid-length (Figs 28-29). Mesosomal thickening long, rounded anteriorly, with slight lateral bulges. Mesosome with 3 microsetae on each side (Fig. 28). Gonopore as in Fig. 29, broad and with prominent distal lobes; 2 microsetae on each side of gonopore. Parameres elongated, slender; pst1-2 as in Figs 28-29.

Female
Thoracic and abdominal chaetotaxy as in Fig. 26 and Tables 2-4. Central sternal plates absent on segments II-VI. Lateral accessory plates present on segments II -VI. Subgenital plate and vulval margin as in Fig. 30, chaetotaxy as in Fig. 30 and Table 3. Subvulval plates broad.

Remarks
Specimens from the two host subspecies diff er slightly in head shape and size (specimens from Tephrodornis virgatus mekongensis are generally larger than specimens from T. v. fretensis; Table 5) and abdominal chaetotaxy (specimens from T. v. mekongensis typically have more tergal setae per segment ranges of the two known host subspecies are separated by a gap in distribution in peninsular Thailand (Robson 2006). We tentatively consider all specimens from both host subspecies conspecifi c.

Diagnosis
The only previously known species of Philopterus from a cardinalid host is P. cardinalis Piaget, 1880 (ex Paroaria coronata (Miller, 1776)); this species is poorly described and illustrated, and has never been redescribed. We have examined 3 specimens (1 ♂, 2 ♀♀) collected by Piaget and labeled as P. cardinalis (NHMUK 010712725-27); however, none of them is in good enough condition to allow proper morphological redescription. An adequate comparison between P. cardinalis and P. stansburyensis sp. nov. must await the redescription of new specimens of P. cardinalis.
The male genitalia of P. stansburyensis sp. nov. and the absence of sternal plates in the Colorado specimens resemble conditions in P. confusio Ansari, 1955 (ex Turdus fulviventris Sclater, 1857). These two species can be separated by the following characters: the posterior projection of dorsal anterior plate short and narrow (shorter than the plate itself) in male of P. stansburyensis sp. nov. (Fig. 33), but long and wide (longer than the plate itself) in male of P. confusio (Ansari 1955: fi g. 7a); lateral slits separating sternites VII and VIII of male subgenital plate long, reaching almost to setal apertures in P. stansburyensis sp. nov. (Fig. 31), but short, just slightly cut out from lateral margin of plate in P. confusio (Ansari 1955: fi g. 7c); female subgenital accessory plates oval or pear-shaped, pointed anteriorly in P. stansburyensis sp. nov. (Fig. 36), but horizontally elongated, pointed medioposteriorly in P. confusio (Ansari 1955: fi g. 7f); vulval setae become shorter medianly and are placed in one row in P. stansburyensis sp. nov. (Fig. 36), but all are short and placed in two rows in P. confusio (Ansari 1955: fi g. 7g). Note that all these comparisons are based on illustrations given by Ansari (1955), which may be of limited reliability.

Description
Head shape and chaetotaxy as in Fig. 33, preantennal area broad. Hyaline margin wide, extending laterally beyond marginal carina. Dorsal anterior plate as in Fig. 33. Ventral anterior plate semi-circular, with slightly concave anterior margin. Coni large, blunt, with round posterior margins, pointing posterolaterally. Gular plate small and narrowly pointed, displaced anteriorly. Thoracic   Male Thoracic and abdominal chaetotaxy as in Fig. 31 and Tables 2-4. Tergite IX+X medianly continuous. Central sternal plates absent on segments II-VI. Holotype with lateral accessory sternal plates on each side of segments III-VI, but in specimens from Colorado these lateral accessory sternal plates not visible. Subgenital plate with deep lateral notches and elongated lateral accessory plate on segment IX+X. Basal apodeme long, slender (Figs 34-35). Mesosomal thickening diff use, with wide extensions distally; 3 microsetae on each side of mesosome. Gonopore elongate, rounded (Fig. 35), with 2 sensilla on lateral margins near distal ends. Parameres completely fused to basal apodeme, slender, with pst1-2 as in Figs 34-35.

Female
Thoracic and abdominal chaetotaxy as in Fig. 32 and Tables 2-4. Gular plate trilobal, with blunt anterior margin. Central sternal plates absent on segments II-VI. Lateral accessory sternal plates not visible. Subgenital plate and vulval margin as in Fig. 36, lateral accessory plates on segment IX+X small and oval. Vulval chaetotaxy as in Fig. 36 and Table 3; vulval setae longest laterally, gradually shortening medianly, with minute median pair. Subvulval plates broadly triangular, with rounded anterior margin. However, P. coriaceus sp. nov. does not key to Mayriphilopterus in the key of Mey (2004), and can be separated from this genus by the following characters: coni present in P. coriaceus sp. nov. (Fig. 39), but absent (possibly highly reduced) in Mayriphilopterus; hyaline margin with thickened setae in Mayriphilopterus, but without such setae in P. coriaceus sp. nov. (Fig. 39); area between subgenital plate and vulval margin with a large number of small setae in Mayriphilopterus, but without such setae in P. coriaceus sp. nov. (Fig. 42). It thus seems unlikely that P. coriaceus sp. nov. is closely related to Mayriphilopterus.
From Osborn's descriptions of both species, and the illustration of P. quiscali (P. agelaii not illustrated in Osborn 1896, but said to be similar to P. quiscali), these two species can be separated from P. coriaceus sp. nov. by the following characters: preantennal head proportionately wider in P. quiscali than in P. coriaceus sp. nov. (Fig. 39); dorsal anterior plate with broad posterior extension in P. quiscali, but with slender posterior extension in P. coriaceus sp. nov. (Fig. 39); tergopleurites of P. quiscali extending only about halfway to midline of abdomen on each side, whereas those of P. coriaceus sp. nov. are much longer in both sexes, almost reaching midline in more posterior segments in male. Chaetotaxy is not given for either P. quiscali or P. agelaii, but Osborn's illustration of P. quiscali has only apertures for 6 setae illustrated on each of the tergopleurites of segment II. In P. coriaceus sp. nov. there are 8 setae placed on each of the tergopleurites of this segment in both sexes (Figs 37-38); however, the number of setae situated median to the tergopleurites in P. quiscali is unknown. In specimens of P. agelaii deposited at the NHMUK, there are 7-8 setae on each side in females and 8-9 setae on each side in males, which overlap with the number of setae in P. coriaceus sp. nov.; one seta on each side is situated median to the tergopleurites in both sexes of the NHMUK specimens of P. agelaii. In addition, Osborn (1896: 220) mentioned "brown spots on each segment back to the eighth [= IX+X]; those on the sixth segment [= VII] form the outer portion of the genital patch." Osborn (1896) further stated that the "lateral spots" of P. agelaii are "small, rather elongated, oblique"; it is not clear whether he was describing the male or the female, but his illustration is of a male. We interpret these spots as the overlap of the median section of the tergopleurites with either the lateral accessory sternal plates (in segments II-VI) or the subgenital plate (segments VII-XI+X). This overlap often shows as darker brown spots than the rest of the tergopleurite. This suggests that the central sternal plates are absent on segments II-VI in P. quiscali and P. agelaii, whereas these are present on male segments V-VII in P. coriaceus sp. nov. (Fig. 37).

Etymology
The specifi c name is derived from Latin 'coriaceo' for 'leather-like', referring to the colour and texture of the abdominal plates.

Description
Head shape and chaetotaxy as in Fig. 39, preantennal area broad. Hyaline margin broad, shallowly concave medianly, extending laterally slightly beyond marginal carina. Dorsal preantennal plate narrowing gently posteriorly, ads situated in transparent section. Ventral anterior plate roughly trapezoidal, anterior margin concave. Coni long, broad, pointed posteriorly. Gular plate large, irregular. Thoracic and abdominal segments as in Figs 37-38. Measurements as in Table 6.

Male
Thoracic and abdominal chaetotaxy as in Fig. 37 and Tables 2-4. Tergopleurite VIII interrupted medianly. Central sternal plates absent from segments II-IV, present but fragmented on segment V, and present on segment VI. Lateral accessory plates present on segments II-IV, present and fused to central sternal plates on segments V-VI. Subgenital plate large, lateral incisions shallow or absent, lateral accessory plate of segment IX+X fused to subgenital plate. Basal apodeme long, rectangular (Figs 40-41). Mesosomal thickening about as broad as long, laterally pointed on dorsal side, with roughly crescentshaped sclerotization in anterior end and triangular sclerotization centrally; 3 microsetae on each side of mesosome. Gonopore bilobed anteriorly, distal part as in Fig. 41. Parameres short, stocky (Figs 40-41); pst1-2 as in Figs 40-41.

Female
Thoracic and abdominal chaetotaxy as in Fig. 38 and Tables 2-4. Tergopleurites VI-IX+X with slight to extensive reticulation median to spiracle openings. Central sternal plates absent on segments II-VI. Lateral accessory plates present on segments II -VI. Subgenital plate as in Fig. 42, reticulation prominent. Lateral sclerotizations of vulval area extended to vulval margin, chaetotaxy as in Fig. 42 and Table 3; short vulval setae thorn-like. Subvulval plates broad, roughly triangular, each with small postero-median projection.
The lack of records of Philopterus complex lice on icterid hosts may be related to the presence of lice of the genus Bizarrifrons Eichler, 1938 on some icterid hosts. This genus belongs to the Brueelia complex (Valim & Palma 2012;Gustafsson & Bush 2017) and is also considered to belong to the 'head louse ecomorph'. Competition may infl uence the distribution of these lice, but more ecological information is needed to assess any potential interactions between these species.
Both P. agelaii and P. quiscali are in need of redescription before an adequate comparison between these species and P. coriaceus sp. nov. can be made. It is not clear what gender of P. quiscali was described by Osborn (1896); however, Emerson (1960) noted that only one female and a nymph are present in Osborn's collection at Ohio State University, Columbus, Ohio. Emerson (1960) designated the female as the lectotype, stating that a female was illustrated. This seems incorrect, as the illustrated specimen has a rounded terminal abdomen and no medianly continuous tergopleurite, suggesting that it is a male. If so, the illustrated male is likely lost. Diagnosis Philopterus pseudohirundo sp. nov. belongs to the same group as other species of Philopterus known from hirundinid hosts (see Table 7). Of these, only P. excisus Nitzsch, 1818(ex Delichon urbicum (Linnaeus, 1758), and P. microsomaticus Tandan, 1955(ex Hirundo rustica rustica Linnaeus, 1758, were illustrated and described in suffi cient detail for an adequate comparison to be made. Characters supporting this relationship include the strongly bilobed hyaline margin (Fig. 45), the somewhat splayed distal male genitalia (Figs 46-47), and the general shape of the head (Fig. 45).
The sclerotized median section of the hyaline margin was not mentioned by either Tandan (1955) or Clay & Hopkins (1960); however, in specimens of P. microsomaticus we have examined, the sclerotized median section is evident. Presumably, this character also occurs in other species of Philopterus from hirundinid hosts, but this has to be verifi ed.

Etymology
The specifi c name is derived from the type host genus. Paratype NO LOCALITY • 1 ♀; same collection data as for holotype; MFN.

Description
Head shape and chaetotaxy as in Fig. 45, preantennal area narrow. Hyaline margin wide, extending laterally beyond marginal carina, deeply concave medianly; weak sclerotization in mid-section. Dorsal anterior plate elongated, shape as in Fig. 45. Ventral anterior plate small, anterior margin deeply concave. Coni small, blunt, directed laterally. Gular plate short, broad. Thoracic and abdominal segments as in Figs 43-44. Measurements as in Table 6.

Male
Thoracic and abdominal chaetotaxy as in Fig. 43 and Tables 2-4. Medianly continuous sternal plates present on segments V-VI, lateral accessory plates present on segments II-IV. Basal apodeme slender , widening markedly in distal end. Mesosome as in Fig. 47, with 3 microsetae on each side. Parameres short, blunt , with pst1-2 apical.

Female
Leg II on both sides of the only examined female missing or distorted, not illustrated. Thoracic and abdominal chaetotaxy as in Fig. 44 and Tables 2-4. Central sternal plates absent, lateral accessory plates present on segments III-VI. Subgenital plate and vulval margin as in Fig. 48; chaetotaxy as in Fig. 48 and Table 3. Lateral sclerotizations of vulval area extended to vulval margin. Subvulval plates elongated triangular.

Remarks
The collection locality is not given on the slide, but the host is restricted to Africa (Turner & Rose 1994), and Zumpt's collections are otherwise mainly from South Africa (Ledger 1980). Conci (1941) described the genus Cypseloecus for the Philopterus species on swallows (Hirundinidae) and swifts ("Cypseli" = Apodiformes); however no Philopterus complex lice occur on swifts, and the name is thus a misnomer. This erroneous host range may be a result of earlier authors believing   (Schrank, 1803)) to be the same as Pediculus hirundinis Linnaeus, 1758 (= Dennyus hirundinis (Linnaeus, 1758)). Clay & Hopkins (1950, 1960 showed that these names refer to diff erent species, of which only the latter occurs on swifts. To date, nine species of Philopterus have been described from swallows (Table 7), all of which fall into the "Cypseloecus" group; if the genus Cypseloecus Conci, 1941 is resurrected, all the species listed here should be included in that genus based on their descriptions and published illustrations. Hopkins & Clay (1952), Price et al. (2003), and Mey (2004) considered Cypseloecus inseparable from Philopterus. Mey (2004) stated that the only notable character of this group is the bilobed state of the hyaline margin. We here describe a new species of Philopterus from a swallow, P. pseudhirundo sp. nov. This species exhibits several characteristics that seem to indicate that the Philopterus from swallows may be more diff erent from Philopterus s. str. than previously believed. However, the relationships within Philopterus s. lat. are poorly known, and it is not clear which morphological characters are useful for the delimitation of groups within Philopterus s. lat.
The most distinctive character of the "Cypseloecus" group is the preantennal area. Compared to most other species of Philopterus, the preantennal area is narrow and elongated in "Cypseloecus," with a deeply concave frons and distinctly bilobed hyaline margin. As can be seen in the species of Philopterus described here, the shape of the preantennal area and the hyaline margin vary greatly between diff erent species in the genus (cf., e.g., Figs 3,9,39). In most of the Philopterus from corvid hosts (including the type species, P. ocellatus; see Price & Hellenthal 1998), the frons is more or less fl at, convex, or only slightly concave. Even in species of Philopterus where the frons is concave (e.g., Fig. 3), the lateral parts of the hyaline margin do not form distinct, narrow lobes as in "Cypseloecus".
In P. pseudhirundo sp. nov., the central part of the hyaline margin is sclerotized (Fig. 45), which makes the head superfi cially resemble that of many species of Philopteroides Mey, 2004. However, this character is not illustrated or mentioned in the descriptions of any other species in "Cypseloecus." We have examined some specimens of P. microsomaticus at the Museum of Natural History, University of Wroclaw, Poland. These all have a median sclerotization similar to that of P. pseudhirundo sp. nov. Presumably, this sclerotization occurs in other species of "Cypseloecus" as well, but we have not examined any of them. No other species of Philopterus from other host families have this sclerotization, but it occurs in many other genera in the Philopterus complex (Mey 2004).
The male genitalia are also distinct in "Cypseloecus," with a rather fl at distal margin of the mesosome and somewhat fl aring parameres . This is unlike the genitalia of most other species described here, which have a more rounded distal margin of the mesosome and more convergent parameres (e.g. , Figs 22-23). However, the type species of Philopterus, and most other species from corvid hosts, have genitalia that are more similar to those of "Cypseloecus" than to most of the other species described here. Moreover, some species of Philopterus on non-hirundinid hosts have genitalia that are intermediate between the two types (e.g., P. stansburyensis sp. nov.; Figs 34-35). Too little is known about the more detailed structure of the mesosome and other parts of the genitalia in the Philopterus complex to make a more detailed comparison.
In our opinion, these diff erences are not suffi cient, based on our current knowledge, to recognize Cypseloecus as a distinct genus within the Philopterus complex, but are perhaps suffi cient to recognize it as a subgenus within Philopterus. Potentially, at least three groups are involved: Philopterus s. str. from corvid hosts, with simple hyaline margin, typically short preantennal areas, and splayed male genitalia; "Cypseloecus" from hirundinid hosts, with a deeply bilobed hyaline margin with median sclerotization, slender and elongated preantennal area, and splayed genitalia; and Philopterus s. lat. (=? Docophorulus Eichler, 1944) from other hosts, with an intermediate hyaline margin, typically short preantennal areas, and convergent parameres. Most likely, the morphological variation in this latter group is suffi cient to recognize further subgeneric or generic groups, some of which may not be recognizable based on published illustrations and descriptions. We do not propose any taxonomic changes at the genus level here, but note that a more thorough revision of Philopterus is needed. Such a revision should, in our opinion, include a consideration of resurrecting Cypseloecus as at least a subgenus within Philopterus. Table 7. Checklist of the known distribution of species of the genus Philopterus Nitzsch, 1818 on swallows (Hirundinidae). Type host species are indicated by an asterisk (*).
These records are most probably the result of human contamination, as discussed by Palma (1994) and Palma & Peck (2013). A lectotype of this species was designated by Palma & Peck (2013). 2) Ledger (1980) considered this species a synonym of P. microsomaticus based on similarities in measurements. Price et al. (2003) listed it as a valid species. 3) Redescribed and partially illustrated by Clay & Hopkins (1960). Additional illustrations in Tandan (1955). 4) Złotorzycka et al. (1999). 5) Balát (1966). 6) Price et al. (2003) listed both hosts as type hosts, thus overlooking that Carriker (1957) selected a lectotype and designated Petrochelidon pyrrhonota as the type host of P. major. No illustration of this species has been published, and the description is very short and unhelpful. This species urgently needs redescription. 7) Ledger (1980). 8) Palma & Barker (1996). 9) Records of P. excisus from Hirundo rustica have here tentatively been interpreted as P. microsomaticus; however, none of this material has been examined for this study, and both P. excisus and P. microsomaticus may occur on H. rustica in diff erent parts of the range. 10) Clayton et al. (1992). 11) Carriker (1956).

Discussion
With the eight species described here, the numbers of known species in the Philopterus complex and the genus Philopterus (including Cypseloecus) are 224 and 193, respectively. All species of the complex described since the publication of the checklist in Price et al. (2003) are listed in Table 8. However, the number of species that can reliably be identifi ed from published descriptions and illustrations is far lower. In general, somatic and setal characters appear to be rather uniform in Philopterus. For instance, all species described here have setal rows on abdominal segments II-VII in both sexes, but the number of setae typically overlaps between species. This suggests that these may be useful to separate closely related species, but less useful to establish relationships between distantly related species. Similarly, the head chaetotaxy is essentially the same in all species described here and varies little within the Philopterus complex in general, with the exception of some preantennal setae. Moreover, apart from diff erences in the development of the ventral and marginal carinae (Mey 2004), the head structure shows less variation within the Philopterus complex than in, e.g., the Brueelia, Oxylipeurus, and Degeeriella complexes.
This relative homogeneity in setal and somatic characters means that the characters that are usually illustrated for species of Philopterus in the published literature (e.g., outlines of heads, dorsal anterior plates, subgenital plates, etc.) are of little use to determine which species are closely related. In contrast, the diff erences in the structure and complexity of the male genitalia are evident from the species described here (cf., e.g., P. afropari sp. nov. (Figs 16-17) and P. coriaceus sp. nov. (Figs 40-41)). The size, shape, and structure of the mesosome, the location and presence or absence of mesosomal setae, the length and shape of the parameres, and the overall structure of the basal apodeme all vary between the species described here. In some cases, the structures seen in one species appear to have no counterpart in other species (e.g., the ventral plates near the anterior end of the mesosome in P. coriaceus sp. nov.; Fig. 41). This variation suggests that male genitalia may be the key to assessing the relationships among species of Philopterus and in evaluating whether or not this genus is monophyletic. Many of the details of the male genitalia illustrated here (e.g., mesosomal sensilla) are generally only visible at high magnifi cations using oil immersion and phase contrast. Limitations in microscope technology may explain why male genitalia have rarely been illustrated in suffi cient detail to be of much use in the past. Notably, many of the characters used to establish species groups within Philopterus by Złotorzycka & Lucińska (1975, 1976 are from the male genitalia. Moreover, it is presently diffi cult to assess patterns of host associations in Philopterus. Mey (2004) summarized the known host distributions of the Philopterus complex genera. Some of the gaps in his summary have now been fi lled (e.g., Tyranniphilopterus on Polioptilidae (Cicchino 2007); Philopteroides on Rhipiduridae (Valim & Palma 2013)), and the discovery of the new genus Vinceopterus Gustafsson et al., 2019 on trogons fell outside the framework of his summary. Nevertheless, few species of Philopterus have been described since 2004 (Table 8), and the outline published by Mey (2004) largely holds true today.
Mey's summary suggests that Philopterus as currently defi ned parasitizes a wide range of hosts representing most of the major radiations of passeriforms. However, the genus is not known from any suboscine hosts, and it appears to be largely replaced by Tyranniphilopterus in many primarily Neotropical host families and by Philopteroides in many exclusively Old World tropical host families; the correct placement of some poorly known Philopterus species from the Australo-Papuan region may also be questionable. The bulk of the species in Philopterus are thus found on host families that occur in the Holarctic. Notably, both Philopteroides and Philopterus are distributed across the two main radiations of Passeriformes, Corvides and Passerida, which may hint at a rich history of host switching in the evolution of the Philopterus complex. However, determining any such patterns of host switching or co-evolution will require a thorough revision of Philopterus. Useful characters to identify groups Table 8 (continued on next 2 pages). Species of the Philopterus Nitzsch, 1818 complex described since the publication of the checklist in Price et al. (2003), with their host associations. The list also includes a few species that have been transferred to the Philopterus complex since 2003 (in Gustafsson & Bush 2017). In cases where a louse species is known from more than one host species or subspecies, the type host species or subspecies is indicated by an asterisk (*). within Philopterus will need to be detected and evaluated before specimens used either for molecular or morphological analysis can be properly identifi ed. The male genitalia appear to constitute an excellent source for such characters, but these need to be better described for almost all known species in the Philopterus complex.