Lunaceps Clay and Meinertzhagen, 1939: 450

Gustafsson, Daniel R. & Olsson, Urban, 2012, 3377, Zootaxa 3377, pp. 1-85 : 5-11

Lunaceps Clay and Meinertzhagen, 1939: 450

( Fig. 1–5)

Type species: Nirmus actophilus ( Kellogg and Chapman, 1899) (by original designation).

Diagnosis: Colour whitish, pale brown, amber, to dark brown, with darker border markings, particularly on abdomen and head. Sexes differ in size, chaetotaxy, terminalia, and genitalic elements.

Head roughly ovoid with broad concave indentation of the posterior margin ( Fig. 1). Hyaline margin narrow, extending laterally to the point where the dorsal preantennal suture reaches the lateral sides of the head. Dorsal anterior plate roughly crescent-shaped. Dorsal preantennal suture arched, and is usually continuous across the head or interrupted medially (but missing in L. limosae and L. paschalis , and interrupted sublaterally in L. holophaeus ). Ventral anterior plate of different shape, and may be rounded, pointed, tapering or flat posteriorly. Pulvinus large and transparent, and associated with one or two pairs of dark structures at the postero-lateral ends. Marginal carina usually clearly defined laterally, though in most species interrupted at least dorsally by the dorsal preantennal suture. Anteriorly, the marginal carina may be interrupted at least ventrally by the anterior extensions of the ventral preantennal suture, which delimit the ventral anterior plate. The marginal carina typically widens inwards at the anterior end of the head, augmenting the ventral anterior plate. Just posterior to the dorsal preantennal suture, there is a broadening of the marginal carina, here termed the lateral nodus, from which the dark preantennal band arises. This band veers off medially, but is usually narrow and fades out as it approaches the middle of the head. In most species, the posterior margin of this band is more clearly defined than the anterior margin. Just before the antennae, the marginal carina broadens ventrally and turns inwards towards the mandibles, for which it seems to provide a socket. An extension of the marginal carina reaches the ventral carina, which is usually well defined posteriorly, but fades when it reaches the dorsal preantennal suture. Dorsally, the marginal carina forms a nodus just anterior to the antennal base, but a usually ill-defined and vaguely pigmented extension continues past the antenna to connect with the preocular nodus, the ocular band, and the postocular nodus, from which it continues as the temporal marginal carina. A thin line runs medially from this nodus to disappear above the mandibles, and we have interpreted this as being what Clay and Meinertzhagen (1939) termed the transversal suture. This line, however, is often very hard to see. Ventrally, the marginal carina divides in two just posterior to the mandibles, with one section continuing as the ventral part of the temporal marginal carina, and the other continuing as the temporal carina. The temporal carina fades out quite abruptly near the posterior margin of the head, and does not seem to reconnect to the temporal marginal carina. Gular plate prominent and usually spade-shaped, in some species with short extensions laterally.

Head setal arrangement as in Fig. 1, though with some variation in relative position. One small spot anterior to the PAS and 3–4 small spots postero-lateral to this, as well as one setae median to MTS1 all probably microsetae. POS positioned on eye. MTS3 and sometimes MTS1 macrosetae, whereas MTS2, MTS4, and MTS5 are small or thorn-shaped.

Mesothorax with lateral sides parallel, shorter than wide. Pterothorax roughly as broad as long in small species or broader than long in larger species, with lateral sides parallel, subparallel, or divergent. In males, three sublateral setae form a triangle (the pterothoracic triangle, see Fig. 2A) at the posterior margin. Median to this are three setae (the pterothoracic row, see Fig. 2A), of which the outermost one is a macroseta. In females, four setae form a row along the pterothoracic margin (pterothoracic row, see Fig. 2B), with a gap between setae number 2 and 3.

Abdomen usually long and slender; widest segment usually V. Tergites transversely continuous apart from segments VIII in males and segment X/XI of both sexes; these are divided medially. Anterior margin of some tergites may be indented medially. Spiracles opening on tergites. Laterally, the tergites wrap around the edge of the abdomen and form paratergal plates on the ventral side. These differ in shape between different species, and are sometimes associated with dark border markings. Tergites III–VII indented antero-laterally by a lighter area, associated with a small bar which extends laterally ( Fig. 4). This bar forms a cap covering the anterior-lateral end of the tergite, and may be elongated anteriorly and re-entrant into preceding segment. Sternites transversely continuous but usually do not reach the lateral margins of the abdomen. Median third of sternite VII in both sexes extended posteriorly, in males to reach posterior end of abdomen. Sternite of female segment VIII divided medially. Setal arrangement almost invariable, apart from size. Intermediate setae of segments III–V macrosetae in both sexes.

Male genitalia as in Fig. 3. Exophallus enveloped by mesomere, which is roughly triangular and interlocks with the parameres anteriorly. Dorsally, there are two anterior thickenings (“dorsal mesomeral fingers”, Fig. 3), which may be convergent or divergent at tip. These are separated by a small gap (“dorsal mesomeral groove”, Fig. 3). Ventrally, the two sides of the mesomere are divided into a pair of squares (“ventral mesomeral blades”, Fig, 3). Laterally, one or more setae can be seen in larger species. Lower endomere kidney-shaped or semicircular. Basal apodeme often with apodemal bridge. Parameres with well developed heads in proximal end, and more or less slender fingers in distal end.

In females, the median part of sternite VII is extended posteriorly into a wedge, which runs between two halves of sternite VIII. Sternite VIII has three sets of setae ( Fig. 5): the posterior marginal setae (often long and slender), the sub-marginal setae (often thorn-shaped or stout, but short), and the median marginal setae (often microsetae). Sternite IX also divided medially, and fused with, extending over, or replacing sternites X/XI. The ventral side of segment IX has three pairs of setae, with the most posterior one typically being longest. Wedge-like extension of sternite VII in some species with dark markings, forming an “amphitheatre”.

Etymology: There is no indication of etymology of Lunaceps in the original generic description. One interpretation is that this name refers to the crescent-shaped dorsal anterior plate of the head. Luna is Latin for “the Moon”; - ceps is Latin for “head”.

Discussion: Lunaceps is easily separated from Quadraceps and other louse genera found on shorebirds by the preantennal area, particularly the shape of the dorsal preantennal suture and the dorsal anterior plate. The male genitalia are quite uniform within the genus, and dissimilar to those of most Quadraceps , but superficially similar to those of Quadraceps spp. ex Tringa spp. There is a tendency in some species for the dorsal preantennal suture to bulge posteriorly to encapsulate the apertures of the AVS, although these extensions never become as extensive as the narrow, elongated furrow in Quadraceps

The female genital setae appear to be very fragile, and vary somewhat between different individuals of the same population, and even between different sides of the same individual. The numbers given are average numbers for all studied material, and we recommended that future work include the study of several individuals before any conclusions are drawn from this set of characters alone. Also, the median-most sub-marginal setae of the female genitalia are occasionally displaced anteriorly, forming a second sub-marginal set. This differs between individuals of the same species, and sometimes between sides of the same individual, and therefore we counted all the submarginal setae as one row.

The species Nirmus cordatus Osborn, 1896 , was included in Lunaceps by Hopkins and Clay (1952). Edwards (1952) erected the monotypic genus Rotundiceps for N. cordatus , but Timmermann (1972: 104) regarded Rotundiceps as a subgenus of Lunaceps . However, there are many differences between these two taxa. Rotundiceps is more “head louse” shaped, with a broad, almost circular abdomen, and a wide head. The head setal arrangement also differs, with MTS1 and MTS2 being long, and the POS being as short and thorn-like as the OS in Rotundiceps . The male genitalia are quite similar, but differ with Rotundiceps having a more constricted mesomere and somewhat more angular parameres than Lunaceps . In contrast, the female genitalia differ widely. The two genera are likely to be closely related.