Hieracolichus Gaud & Atyeo, 1975

Hernandes, Fabio A., 2020, A review of the feather mite family Gabuciniidae Gaud & Atyeo (Acariformes Astigmata: Pterolichoidea) of Brazil, with descriptions of eleven new species, Zootaxa 4747 (1), pp. 1-53 : 28-29

Genus Hieracolichus Gaud & Atyeo, 1975

Type species: Pterolichus nisi Canestrini, 1878 , by original designation.

The genus Hieracolichus had previously included ten species ( Gaud & Mouchet 1959, Gaud & Atyeo 1975, Gaud 1983, Mironov et al. 2018), all from hosts of the family Accipitridae (Accipitriformes) : H. nisi ( Canestrini, 1878) from Accipiter nisus (Linnaeus, 1758) , H. hirundo ( Mégnin & Trouessart, 1884) from Harpia harpyja (Linnaeus, 1758) , H. dobyi ( Gaud & Mouchet, 1959) from Stephanoaetus coronatus (Linnaeus, 1766) , H. ramosus ( Gaud & Mouchet, 1959) from Pernis apivorus (Linnaeus, 1758) , H. similis ( Gaud & Mouchet, 1959) from Polyboroides typus pectoralis Sharpe 1903, H. africanus Gaud, 1983 from Gyps africanus Salvadori, 1865 , H. monachi Gaud, 1983 from Aegypius monachus (Linnaeus, 1766) , H. orthochaetus Gaud, 1983 from Gypohierax angolensis (Gmelin, 1788) , H. ostodus Gaud, 1983 from Aviceda cuculoides Swainson, 1837 , and H. philippinensis Mironov et al. 2018 from Pithecophaga jefferyi Ogilvie-Grant, 1896 . Two species, however, should be removed from this genus: Mironov et al. (2007) suggested that H. ostodus probably belongs to the Aposolenidia genus group, and Mironov et al. (2018) noticed that Hieracolichus hirundo should be transferred to Aetacarus .

In the original description of Hieracolichus ostodus, Gaud (1983: 759) noted the remarkable uniqueness of this species, and even suggested it might be better placed in a separate new genus, but decided to postpone this decision until further knowledge was acquired. After having examined the holotype and paratypes of H. ostodus deposited at USNM and MRAC, respectively, I subscribe to the opinion that this species is remarkably different from all others of this genus, noticeably in: 1) lacking solenidion σ on genua III, 2) having bases of epimerites I and II inflated into large ball-like, darkly sclerotized structures, and 3) epimerites I basally connected by a transverse bridge. With the exception of the first character, the two latter characters put H. ostodus very close to the definition of the genus Proaposolenidia Mironov & Proctor, 2007 , which has included so far only two species bearing the solenidion on genu III. However, as new knowledge is gathered, it seems that the definition of the genus Proaposolenidia should be broadened to accommodate two more species in which this solenidion is absent, P. plumbea sp. nov. and H. osto- dus. The new combination for the latter species is herein proposed as Proaposolenidia ostoda ( Gaud, 1983) comb. nov.

As for H. hirundo , both Gaud & Atyeo (1975) in creating the genus Hieracolichus , and Hernandes (2017) in the redescription of that species, overlooked the fact that females have setae g much closer to 4b than to 4a, and genital papillae that are situated distinctly anterior to setae 4a; these are the two diagnostic characters of the genus Aetacarus . Although these characters may seem dubious in nature, in all Hieracolichus females setae g are closer to 4a and placed slightly anterior to or at the same level of genital papillae (vs setae g closer to 4b than to 4a – or equidistant between those setae – and genital papillae anterior to 4a in Aetacarus ). Gaud & Atyeo (1975) recognized the great similarity between these two genera, and acknowledged that males alone could not be distinguished from one another other than merely with specific differences. I suspect, however, that these genera might eventually constitute a uniform and monophyletic taxon, although the mentioned female characters might be useful to distinguish species groups or just species. A complete phylogeny of the group using both morphology and molecular tools could solve this riddle. Until then, Hieracolichus hirundo must be transferred to Aetacarus , and provided with a new valid name Aetacarus hirundo ( Mégnin & Trouessart, 1884) comb. nov. In summary, with the removal of H. ostodus and H. hirundo to Proaposolenidia and Aetacarus , respectively, and the description of two new species below, the genus Hieracolichus incorporates 10 described species.

With regard to the host associations, all but one species occur on accipitriform hosts, the exception being H. falcon sp. nov. described below from a falconiform host. Additionally, one undescribed Hieracolichus species was reported from a falconid ( Daptrius ater Vieillot, 1816 ) in Colombia ( Barreto et al. 2012). Although superficially similar in form, current phylogenetic analyses place eagles and falcons to quite distantly related bird orders, Accipitriformes and Falconiformes , respectively ( Prum et al. 2015; Mindell et al. 2018). It is conceivable that the acquisition of Hieracolichus mites by falcons may be the result of the horizontal transfer from some accipitriform host.