Picophilopterus Ansari 1947

Picophilopterus Ansari, 1947

Type species: Picophilopterus tuktola Ansari, 1947: 265 [= Pediculus pici Fabricius, 1798: 571] (by original designation).

Diagnosis. There are no good published illustrations to distinguish Picophilopterus from Penenirmus morphologically, especially regarding male genitalia, features of the head and its chaetotaxy. However, based on specimens available to us, the comparison between the two genera published by Mey (1992) and the redescription of the type species of Penenirmus by Sychra et al. (2014), these genera can be separated by the following characters: (1) Penenirmus lacks the ventral horns (VH in Figs 6, 8) in the male endomere, which are present in Picophilopterus (“sharp pointed lateral projection” of Carriker 1963: 33; “endomeralen Skleritpaar” of Mey 1992: 50); (2) Picophilopterus lacks the dorsal postantennal suture, but is present in Penenirmus (Figs 3–4); (3) the antero-median indentations of the tergopleurites present in at least some Penenirmus are lacking in Picophilopterus (Figs 1–2); (4) at least the type of Penenirmus has multiple sts on each of segments II–VI, but species of Picophilopterus generally only have one sts on each side, except for Picophilopterus campephili (Eichler, 1953a) that has two sts on each side (see Dalgleish 1972: figs 7–8).

Carriker (1963) suggested that the structure of the preantennal head and the number and lengths of the abdominal setae would separate these genera; however, even between species where the head shape differs significantly, the structure and chaetotaxy appear to be largely the same, and the numbers of dorsal abdominal setae appear to overlap among species of the two genera. The ventral “elongated lateral sclerites bearing three minute, spine-like setae” mentioned as a generic character for Picophilopterus by Carriker (1963: 33) differ only in shape between Picophilopterus and Penenirmus [compare our illustrations with those of Sychra et al. (2014)], and the shape of the “three minute, spine-like setae” is different even among species of Picophilopterus.

Mey (1992) suggested that the shape of the ventral carina separates these genera, but this is not the case for Picophilopterus blythipici n. sp. or for the specimens of Picophilopterus pici sensu lato we have examined. Differences in the size and shape of the coni suggested by Mey (1992) may be more useful, but we have not seen enough species of either genus to evaluate this feature adequately. Mey (1992) also suggested that the relative length of the os compared to mts1 and mts3 separates Picophilopterus from Penenirmus, but this is not true for all Picophilopterus [including P. serrilimbus (Burmeister, 1838) illustrated by Mey (1992)].

Description. Both sexes. Head rounded trapezoidal (Fig. 3), preantennal area differing in shape between species. Hyaline margin without marginal sclerotisation, and limited laterally to frons. Marginal carina interrupted medianly and laterally. Dorsal preantennal suture completely surrounds dorsal anterior plate and reaches lateral margin of head near site of as1; suture may extend posteriorly along midline posterior to dorsal anterior plate. Ventral anterior plate present. Ventral carina divided medianly, extended anteriorly to approach or reach frons. Head chaetotaxy as in Fig. 3; pas and pos absent; avs3 not displaced anteriorly, situated near bend of ventral carina; mts2 macroseta or microseta; s5–7 absent. Dorsal postantennal suture absent. Gular plate present, often with central decoration. Thoracic and abdominal segments as in Figs 1–2. Claws of all feet of dissimilar size (Figs 1a–c), and tarsus I of all feet with small, flattened hyaline seta on median margin (hs in Figs 1a–c). Tergopleurites II–VII and IX+X in male and II–IX+X in female medianly continuous. Sternites present but lightly sclerotised.

Male. Subgenital plate formed from sternal plates VII–VIII, may reach distal margin of abdomen (Fig. 1). Genital opening clearly dorsal, posterior end of abdomen strongly sclerotised. Basal apodeme long, tongue-like (Fig. 5). Parameres fused to basal apodeme; pst1 sensilla, pst2 microsetae, in some species very stout. Endomere elongated, with postero-lateral extensions on which three slender setae are situated on each side. Ventrally, endomere has paired horn-like projections (Fig. 6). Distal endomere elongated. Lateral to endomere are paired elongated plates of unknown derivation, each with three small setae at about middle of length; anteriorly these plates appear to be fused to basal apodeme, but this is not clear in specimens examined. Distal to endomere, median to the parameres, is a hyaline section of the genitalia which is poorly visible. The lateral extent of this section is not visible, and for clarity only distal margin is illustrated; no setae are visible on this margin in specimens examined.

Female. Subgenital plate formed from sternal plate VII only (Fig. 2), bulging posteriorly along midline, but not reaching or approaching vulval margin. Subvulval plates present. In species examined by us, lightly sclerotised plates are present near vulval margin (Fig. 9). Vulval chaetotaxy with multiple long, slender setae marginally, microsetae submarginally forming convergent rows near midline, and scattered setae present between vulval margin and subgenital plate.

Host distribution. Piciformes: Capitonidae and Picidae.

Geographical range. All continents, except for the Australo-Papuan Region and Antarctica, where there are no woodpeckers or Neotropical barbets.

Remarks. Dalgleish’s (1972) extensive synonymy of described taxa and expansion of the known host ranges of several species of Picophilopterus (as Penenirmus) are based primarily in similarities in abdominal chaetotaxy. Other characters, such as head shape and limited details of the male genitalia, suggest that many of the species considered junior synonyms by Dalgleish (1972) are in fact distinct species, including P. caurensis Carriker, 1963, P. rivollii Carriker, 1963 and P. tuktola Ansari, 1947. A thorough revision of the genus Picophilopterus is needed to establish whether or not the wide host associations reported by Dalgleish (1972) are accurate. Here, we follow the species-level taxonomy of Dalgleish (1972) and Price et al. (2003).

In addition, redescriptions of species from non-picid hosts are needed to establish the limits of Picophilopterus. In the phylogeny of Johnson et al. (2021: fig 1), Penenirmus jungens (Kellogg, 1896b) is separated from a large clade including many specimens identified as Penenirmus auritus (Scopoli, 1763), one of each of P. arcticus (Carriker, 1958), P. marginatus Tendeiro, 1958, P. pici and P. zumpti Tendeiro, 1961, plus several as Penenirmus sp. [we regard most of these taxa as belonging to Picophilopterus]. To reflect these results into the taxonomy of the complex, the species from honeyguides and some African barbets (Lybiidae) may need to be included in Picophilopterus in order for this genus to be monophyletic, but we believe there are still not sufficient available data to do so. Similarly, Penenirmus zumpti, and P. leucomelan Tendeiro, 1961 are morphologically close enough to Picophilopterus to be included in this genus, but we refrain from making these transfers until these species are properly redescribed. Judging from its original description, Penenirmus marginatus appears to be distinct, and not close to either Picophilopterus or the species parasitising African barbets.

The correct generic position of Penenirmus jungens is not clear, although we have tentatively placed it in Picophilopterus. The keys of Emerson & Johnson (1961) and Dalgleish (1972) indicate that this species is morphologically close to other species of Picophilopterus; however, these keys are based mainly on abdominal chaetotaxy, which may not be useful to separate genera in the Penenirmus -complex. Furthermore, Emerson & Johnson’s (1961: figs 6, 14, 24) illustrations of P. jungens, i.e. the dorsal anterior plate, the pterothoracic margin and the vulval margin, are characters which may not vary sufficiently among the genera of the Penenirmus -complex to allow placing P. jungens with certainty.

More species of the Penenirmus -complex need to be properly redescribed to establish whether the species from African barbets and honeyguides should be included in Picophilopterus, or if these species and P. jungens should be placed in separate new genera.