Included genera:

Calidolipeurus Gustafsson et al., 2020b: 2.

Cataphractomimus Gustafsson et al., 2020a: 206.

Chelopistes Kéler, 1940: 180.

Virgula Clay, 1941: 119.

Eiconolipeurus Carriker, 1945: 91.

Epicolinus Carriker, 1945: 104.

Gallancyra Gustafsson & Zou, 2020a: 11.

Megalipeurus Kéler, 1958: 327.

Oxylipeurus Mjöberg, 1910: 91.

Pelecolipeurus gen. nov.

Reticulipeurus Kéler, 1958: 332.

Subgenus: Reticulipeurus (Forcipurellus) Gustafsson & Zou, 2023:497.

Subgenus: Reticulipeurus (Reticulipeurus) Kéler, 1958: 332.

Sinolipeurus Gustafsson et al., 2020a: 229.

Splendoroffula Clay & Meinertzhagen, 1941: 343.

Splendopeurus Kéler, 1958: 309.

Talegallipeurus Mey, 1982: 242.

Trichodomedea Carriker, 1946: 365.

Valimia Gustafsson & Zou, 2020b: 490.

The Oxylipeurus-complex is widely distributed across galliforms, being absent only from numidid hosts (Table 2); the genus Afrilipeurus Mey, 2010, was originally described from species known from numidid hosts, but this genus appears to be a member of the Lipeurus-complex (see below) and only superficially similar to lice in the Oxylipeurus-complex. Amongst the genera within the Oxylipeurus-complex, most are restricted to certain host groups.

There is a clear division in the Oxylipeurus-complex between genera occurring mainly on New World host groups and those occurring mainly on Old World host groups. With the exception of Chelopistes lervicola (Clay, 1941), all members of the genera Chelopistes Kéler, 1940, Eiconolipeurus Carriker, 1945, Epicolinus Carriker, 1945, Labicotes Kéler, 1940, Trichodomedea Carriker, 1946 and Valimia Gustafsson & Zou, 2020b, are found only on New World hosts. In contrast, the genera Megalipeurus Kéler, 1958, Pelecolipeurus gen. nov., Calidolipeurus Gustafsson et al., 2020b, Cataphractomimus Gustafsson et al., 2020a, Gallancyra Gustafsson & Zou, 2020a,. and Sinolipeurus Gustafsson et al., 2020a, are only found on Old World hosts. The genera Oxylipeurus Mjöberg, 1910 and Talegallipeurus Mey, 1982, are exclusively known in Australia and Wallacea. That leaves only one cosmopolitan genus, Reticulipeurus Kéler, 1958, which is known both in the Old and New Worlds.

Reticulipeurus also has wider host associations than most other genera in this complex, being known from both Cracidae and Phasianidae II–III. However, the species known from Phasianidae III belong to a different subgenus (Gustafsson and Zou 2023). The species from cracid hosts have not been revised in recent years and may represent a separate radiation. Reticulipeurus, as currently understood, may represent a plesiomorphic morphotype, from which other, morphologically more distinct, groups of Oxylipeurus-complex lice, have evolved. If not, the distribution of Reticulipeurus on two distinct host groups – mainly Asian phasianids and almost entirely Neotropical cracids – requires further study to understand.

Similarly, Gustafsson et al. (2020a) noted that the widely distributed genus Megalipeurus slightly differs morphologically amongst different host groups and may also represent several distinct lineages. Most other genera are more restricted: Eiconolipeurus and Epicolinus on odontophorid hosts, Labicotes on cracid hosts, Trichodomedea on cracid and odontophorid hosts and Calidolipeurus, Gallancyra and Valimia being known from one host genus each. The perplexing distribution of the genus Chelopistes was discussed in detail by Mey (2006).

Notably, the genera in the tragopan group are hosts to three genera of Oxylipeurus-complex that are, so far, not known from hosts outside that clade (Cataphractomimus, Pelecolipeurus, Sinolipeurus). The distribution of lice in these genera on the hosts of this radiation is summarised in Table 3. In at least one case, lice from all three genera are known from the same host species, echoing the radiation into three congeneric species of the genus Valimia on the same host species (Gustafsson and Zou 2020b). To date, there is no example of all three genera occurring on the same host individual. However, data from any galliform host are rather limited, not least because many birds in this radiation are protected. Examinations of birds in, for example, rescue centres may be necessary to establish whether the three Oxylipeurus-complex genera on hosts in the tragopan group ever co-occur on the same host individual and, if so, if they then partition the plumage amongst them.

Lice in the Goniocotes-complex are conspicuously absent from both the mainly New World host radiations, Odontophoridae and Cracidae, as well as from all New World genera in the other host radiations. The sole exception is the turkey, which is sometimes parasitised by Goniocotes gallinae (Linnaeus, 1758), normally found on domestic chicken. Goniocotes gallinae never seems to be reported from wild turkey in their native range (e.g. Hightower et al. (1953); Kellogg et al. (1969); Nelder and Reeves (2005); Cruz et al. (2013); Camacho-Escobar et al. (2014)) and this host association is likely based only on domestic birds which have been in contact with domestic chicken. Based on current knowledge, the Goniocotes-complex would, thus, seem to be an exclusively Old World radiation.

Based on the structure of the male genitalia, lice of the Goniodes-complex, listed from megapodiid hosts in Table 2, are likely more closely related to Goniocotes than to Goniodes. Mey (1997) circumscribed the genera on megapodiid hosts as a distinct group, but excluded the one known Goniocotes species from this group. If this group is considered part of the Goniodes-complex (as by, for example, Price et al. (2003)), it must be considered an aberrant group within this genus. The only known Goniocotes species from a megapodiid host may, as Mey (1997) pointed out, be evidence either of a secondary infestation or of a relict association.

Goniocotes sensu lato is widely distributed across Old World landfowl (Table 2) and do not show any obvious patterns of distribution. At least six morphologically different groups can be found within Goniocotes, but the relationship between these groups is unclear. Only one of these groups, Goniocotes I, is widely distributed across Numididae and Phasianidae I–III. The poorly-known Goniocotes II group is only known from numidid hosts, where it may overlap in distribution with species in Goniocotes I. Goniocotes III–IV are only known from the Congo peafowl and both groups are poorly known and may not be closely related to the rest of Goniocotes (see Clay (1938b)). A fifth group, only known from peafowl, was recently described as the genus Pavoniocotes Gustafsson et al., 2023.

The distribution patterns of the sixth group, previously called Dictyocotes Kéler, 1940, mirrors that of the three Oxylipeurus-complex genera summarised in Table 3, being found mainly on hosts in the tragopan group. However, some species of Dictyocotes are also known from hosts in the genus Crossoptilon Hodgson, 1838, another high-altitude group of birds, mainly distributed in and around China. The presence of a mesosome in the male genitalia in this group, as well as other morphological characters, suggests that Dictyocotes should be separated from Goniocotes; this will be discussed in more detail elsewhere (DRG, in prep.).

The Goniodes-complex is by far the most diverse of the ischnoceran louse groups known from galliform hosts and almost half (28 of 60; 46.7%) of the groups identified in Table 2 belong to this complex. Of these, at least eight currently have no genus-level name and, with the exceptions of Pachyskelotes Kéler, 1940 and Passonomedea Carriker, 1944, all were treated as members of a highly polytypic Goniodes by Price et al. (2003). To discuss the distribution of morphologically distinct groups within this complex, we here follow Mey (2009) in resurrecting numerous older names within this complex and use the numbers 1–8 to denote some groups that have no available genus names. We deviate from Mey (2009) only in considering Zlotorzyckella Eichler [in Eichler and Vasjukova 1981], 1981, as a synonym of Oulocrepis Kéler, 1940. Note that, as some species in this complex have never been adequately described or illustrated, the exact limits of these proposed genera and groups is in some cases tentative. A small number of species are so poorly described that they are noted as “Unknown” genera in Table 2 and not discussed further here.

Goniodes-complex lice are unknown from cracid hosts and if the Goniodes-complex genera parasitising megapodiid hosts discussed above are moved to the Goniocotes-complex, no Goniodes-complex lice would be known from members of this host family either. Otherwise, lice in the Goniodes-complex occur across all major radiations of galliforms. However, only three groups within this complex could reasonably be said to be widely distributed: Oulocrepis Kéler, 1940, Solenodes Kéler, 1940 and Stenocrotaphus Kéler, 1940. The remaining genera and groups in this complex are known only from single host families or even single host genera (Table 2). Stenocrotaphus is mainly known from numidid hosts and African and South Asian francolins and spurfowl, but has, secondarily, also become established on chicken.

Oulocrepis is more widely distributed, occurring on many different host genera in Phasianidae I–II. Morphological variation, above all, in the male genitalia in this group is large (see, for example, Clay (1940)) and, above all, the type species (Goniodes dissimilis Denny, 1842) is somewhat different from all other species in the group with regards to head shape and male genitalia; however, other characters, such as female genitalia, indicate a close relationship. The genus as circumscribed here seems to be established on hosts in different geographical regions, from the Arctic to Sub-Saharan Africa and, in many cases, seems to occur on the same host species as other Goniodes-complex lice.

Solenodes is a widely distributed group, which as circumscribed here, occurs on hosts from Odontophoridae and Phasianidae I–II. Notably, most of the hosts of species in Solenodes are associated with drier grasslands. The male genitalia of this group are more reminiscent of those of the Goniocotes-complex than those of any other group of Goniodes-complex lice; however, as these genitalia are much reduced in complexity, it is possible that the group is artificial and, in reality, comprises several different lineages. Several species here placed in this genus are poorly described and illustrated and a revision of the group is needed to establish its limits.

The tragopan group of birds is collectively parasitised by four Goniodes-complex genera, of which only one presently has a proposed name: Margaritenes Kéler, 1940; the others are here referred to as Genera 2–4. Amongst these, only Genus 2 and Genus 3 appear to be closely related, sharing similarities in the structure of the male antennae and a unique fusing of the pteronotum and tergopleurite II. Potentially, as these species are studied in more detail, further similarities may be found, but, at present, there seems to be nothing to indicate that all four genera are part of the same radiation within the Goniodes-complex.

Lice in the Lipeurus-complex are the most morphologically homogeneous amongst the groups of ischnoceran lice occurring on galliforms. Lice in this complex are unknown from all New World hosts, except the turkey, which is parasitised by Lipeurus caponis (Linnaeus, 1758) naturally found on domestic chicken. Two genera in this complex are known from numidid hosts only (but secondarily established on domestic chicken) and three genera are unique to the Megapodiidae (Table 2). Based on the structure of the tergopleurites, female genitalia, male subgenital plate, abdominal chaetotaxy and other characters, it seems likely that Afrilipeurus belongs in this complex (see below); thus, three different genera occur on numidid hosts, although only two genera are known to occur on the same host genus. As with the Goniodes- and Oxylipeurus-complexes, the Lipeurus-complex genera known from megapodiid hosts are unique to that radiation, highlighting the distinction of the louse fauna on megapodes.

No Lipeurus-complex species have been described from any species of Tetraophasis or Tragopan and the only species of the genus Lipeurus known from Lophophorus spp. needs verification and may represent a contamination. As both Lipeurus- and Oxylipeurus-complex lice are of the wing louse ecomorph, it is conceivable that the multitude of Oxylipeurus-complex lice on hosts in the tragopan group have prevented Lipeurus-complex lice from establishing themselves there. However, the louse fauna of many members of the tragopan group remain poorly known and the absence of Lipeurus-complex species on these hosts needs verification. Moreover, the mechanisms of interspecific competition in lice are poorly known and cases are known where the same host species is parasitised by multiple louse species of the same ecomorph (e.g. head lice on common blackbird; Oslejskova et al. (2020)).

Several smaller groups of ischnoceran louse genera are also known from galliform hosts. Of these, Megapodiella Emerson & Price, 1972, is only known from megapodiid hosts, Colinicola Carriker, 1946, only from odontophorid hosts, Lerwoecus Mey, 2006, only from Lerwa lerwa (Hodgson, 1833) and Galliphilopterus Emerson & Elbel, 1957, only from Arborophila brunneopectus Blyth, 1855. It should be noted that Colinicola may be polytypic, based on the structure of the male genitalia and other characters, but this has no major implications for the distribution of this genus. The remaining two genera, Cuclotogaster Carriker, 1936 and Lagopoecus Waterston, 1922, are more widely distributed.

Cuclotogaster is known from hosts in Odontophoridae and Phasianidae I–III; however, the species from New World odontophorid hosts needs verification and may be an introduction following the European colonisation of the Americas. Otherwise, Cuclotogaster is absent from all New World hosts, despite being widely distributed in the Old World. Species of Cuclotogaster from Arborophila spp. are morphologically different from other species, with much narrowed male genitalia and possibly some differences in the tergopleurites and the female genitalia; these characters are poorly studied. The genus has not been thoroughly revised since Clay (1938a) and the overall variation in Cuclotogaster is poorly known. Notably, most known hosts are in Phasianidae I and are associated with drier, open country (e.g. savannah, grassland). Species occurring on hosts outside this radiation also often share the same kind of habitat, suggesting that host-switching between sympatric host species may have occurred.

In contrast, the genus Lagopoecus is mainly known from hosts in the Phasianidae II radiation, with a few species known from hosts in Phasianidae I; at least the association with domestic fowl may be due to straggling in domestic settings. Species of Lagopoecus occur in both the Old and New World and are often associated with more boreal or mountain- or forest-dwelling hosts, but exceptions are known (Table 2). In general, Lagopoecus occurs on lowland hosts in the boreal area, but seems more restricted to mountain-dwelling hosts further south and is largely absent south of the Equator.

Galliforms in the tragopan group are parasitised by lice in the genus Lagopoecus, but no species of Cuclotogaster are known from these hosts. The Lagopoecus species parasitising Lophophorus spp. are morphologically distinct, lacking the dorsal pre-antennal suture, but species known from Tragopan spp. are not similar to these and do not appear to be closely related. The genus Lagopoecus has not been comprehensively reviewed since Clay (1938a) and the patterns of variation are poorly known. Nevertheless, based on our current knowledge, there is nothing to suggest that the Lagopoecus species on tragopan group hosts form a unique radiation within this genus.

It is clear from this brief overview that no single factor can be used to explain distribution patterns amongst the Ischnocera that parasitise galliform hosts. Overall, both host phylogeny, host biogeography and host ecology appear to influence the known host associations in the groups included in Table 2. Moreover, in some cases, it is not clear which factors are most important, as several factors overlap.

Undoubtedly, host phylogeny is an important factor structuring host associations in louse communities on galliforms. For instance, there appears to be little overlap between the lice of megapodiid hosts and other landfowl (Table 2), likely reflecting that megapodiids are the sister group of all other galliforms (Kimball et al. 2021). Similarly, many of the groups of lice occurring on numidid hosts do not occur on other host groups naturally (but some have spread to, for example, domestic chicken in domestic settings). Numerous smaller groups are also limited to one or a few closely-related genera, especially in the Goniodes-complex.

There is also a distinct difference between most of the New World and Old World galliforms, with Trichodomedea being shared by two New World host families, but absent on all Old World hosts and most Cuclotogaster and Goniocotes being absent from New World hosts despite being widely distributed across the Old World. Notably, African odontophorids are not parasitised by the same lice as New World members of this family, but by Cuclotogaster, which is widely distributed on other African hosts.

Contrasting with the large-scale biogeographical pattern, some patterns may have more to do with host biotope than with faunal regions. For instance, even if Cuclotogaster is largely limited to hosts in Phasianidae I, the genus also occurs on some members of Phasianidae II that occur in less forested areas, such as Phasianus Linnaeus, 1758 and Perdix Brisson, 1760 (Table 2). Similarly, Oulocrepis is found across both these radiations, often on birds that inhabit more open, grassy areas; Solenodes and Stenocrotaphus also appear to be distributed mainly on hosts in the same type of biotope and include at least some species in other host radiations.

Notably, some patterns cannot easily be explained and may be due to gaps in our knowledge or on incorrect classification of known species. It is, for instance, curious that the widely-distributed genus, Reticulipeurus, should occur on both Old World phasianids and New World cracids, despite all other ischnoceran lice on cracids being specific to the New World. Based on published data, there are no obvious morphological differences between the species on these host groups, although the species of cracids have not been revised in recent decades and few detailed illustrations have been published. The distribution of the genus Megalipeurus is also difficult to understand, but the genus is morphologically heterogeneous and a revision of the group may reveal that the current circumscription is artificial (Gustafsson et al. 2020a).

It is worth noting that elevation may influence distribution patterns. Several distinct genera and groups are known only or mainly to infest high-elevation hosts, such as Lerwoecus and many of the unnamed groups within the Goniodes-complex. In contrast, low-elevation hosts are often parasitised by more widely-distributed louse genera (e.g. Lipeurus, Oulocrepis, Goniocotes I).

Most relevant to the taxa described here are those found in the tragopan group, all of which are high-elevation birds within Phasianidae II (Kimball et al. 2021). With the exception of an unconfirmed Lipeurus species occurring on one of the species of Lophophorus, all of the typically low-elevation groups of Ischnocera are absent from hosts in the tragopan group. However, the diversity of lice in this group is considerable. Despite comprising only ten species in three genera, the species in this group are collectively hosts to at least three Oxylipeurus-complex genera (Table 3), as well as a morphologically distinct group of Lagopoecus, four genera within the Goniodes-complex and almost all the known species of Dictyocotes. With the exception of Dictyocotes, all these genera and groups are unique to hosts in the tragopan group. This pattern may also be mirrored in the Amblycera. Price and Beer (1964) considered Colpocephalum tetraophasis Price & Beer, 1964, “rather unique”, but did not detail in what way; Amyrsidea impejani Scharf [in Scharf and Price], 1983, was also described as having some distinct morphological characters, rare for the genus.

Possibly, the relevant factors structuring these host associations are a mixture of host phylogeny – all the hosts, except Crossoptilon are closely related – and habitat factors – all the hosts including Crossoptilon are high-elevation birds. The overlap in range varies between species pairs, but, in at least some cases, the hosts in these genera co-occur and may even forage together (Madge and McGowan 2002). More data are needed from all hosts in the genera Lophophorus, Tetraophasis and Tragopan, as well as from other high-altitude galliforms, to evaluate the louse community parasitising these hosts and their relationship to related lice on other galliforms.

Future collections may also help determine the extent to which the three genera of Oxylipeurus-complex lice on T. temminckii co-occur on the same host population. All three species are known from Sichuan Province, China, but from different collection events and areas within this Province. The co-occurrence of three congeneric species of lice in the Oxylipeurus-complex was recently reported from turkey (Gustafsson and Zou 2020b) and cases such as these could give insights into the process of microhabitat partitioning in chewing lice and potentially into the process of higher-level radiation of lice on hosts.

Here, we update the genus-level key to the Oxylipeurus-complex previously published by Gustafsson et al. (2020b) and emended by Gustafsson and Zou (2023) after the description of the subgenus Reticulipeurus (Forcipurellus). We here remove the genus Afrilipeurus from this complex, based on the justification below and include the genus Pelecolipeurus.

We believe it is justified to remove the genus Afrilipeurus from the Oxylipeurus-complex and,instead, place it in the Lipeurus-complex, where it is probably closely related to Numidilipeurus Tendeiro, 1955, which occurs on the same host group. This is based on the following morphological comparisons:

1. Amongst slender-bodied Oxylipeurus-complex genera, abdominal chaetotaxy consists of only sutural setae and principal post-spiracular setae dorsally and only one sternal seta on each side on segments II–V ventrally. In the Lipeurus-complex, multiple sternal setae per segment are the norm and, in the genus Numidilipeurus, both multiple sternal setae and tergal posterior setae are present on tergopleurites II–VIII. Afrilipeurus has multiple sternal setae and tergal posterior setae present on segments II–VIII.
2. Tergopleurites are medianly divided in all Oxylipeurus-complex genera except Talegallipeurus Mey, 1982, in which tergopleurites VII–IX+X are apparently medianly continuous; moreover, intertergal plates are absent in all Oxylipeurus-complex genera. In Lipeurus and Numidilipeurus, tergal plates are medianly continuous and intertergal plates are common in males, but do not occur in all species. In Numidilipeurus, intertergal plates are present on at least male segments III–V. Afrilipeurus has medianly continuous tergopleurites and intertergal plates on male segments III–IV.
3. Female genitalia lack distally convergent rows of vulval oblique setae in the Oxylipeurus-complex and this set of setae is often reduced to one or a few short setae on the posterior margin of abdominal segment VII. In Numidilipeurus, these setae are numerous (> 5 per side) and form roughly convergent rows on the ventral side of segments VII–IX+X, which is the same as in Afrilipeurus.
4. Marginal temporal seta 1 is at least a mesoseta in Afrilipeurus and Numidilipeurus, but always a microseta in the Oxylipeurus-complex.
5. Despite considerable variation amongst genera, the male terminalia in the Oxylipeurus-complex are rather uniform in their basic structure, with a generally rounded ano-genital opening, anterior to which may be a transverse sclerotisation that may be continuous with the subgenital plate; several setae of varying length are situated anterior to this opening and a maximum of one seta on each side (typically none) is situated on the ventral side of the poorly-sclerotised areas postero-lateral to the ano-genital opening. Even in genera such as Pelecolipeurus, where the ano-genital opening is not clearly visible, its position can be judged by the distribution of setae and the anterior sclerotisation and this structure appears to be found even in the genus Labicotes Kéler, 1940, in which the stylus is absent. The terminalia of the Lipeurus-complex males are more variable, but do not include a transverse sclerotisation and the non-sclerotised areas distal to the subgenital plate may form a longitudinal groove, with multiple setae on each side; this is, for instance, the case in some Numidilipeurus. In Afrilipeurus, there is no transverse sclerotisation and there are multiple small setae on each side lateral to a longitudinal groove.
6. The female subgenital plate is never extended much distal to the row of sternal setae of segment VII in the Oxylipeurus-complex, but is extended distal to this row in Lipeurus-complex and in Afrilipeurus.

For these reasons, we here exclude Afrilipeurus from the Oxylipeurus-complex and transfer it to the Lipeurus-complex, where it is probably close to Numidilipeurus.