Revision of New World Loxocera ( Diptera : Psilidae ) , with phylogenetic redefinition of Holarctic subgenera and species groups

The New World species of Loxocera Meigen are revised including two new species, L. (Imantimyia) ignyodactyla Buck sp. n. from Costa Rica (first record of the genus from the Neotropical region) and L. (Imantimyia) ojibwayensis Buck sp. n. from Ontario, Canada. Loxocera californica Capelle is synonymized with L. collaris Loew and lectotypes are designated for L. pleuritica Loew and L. cylindrica var. obsoleta Johnson (both synonyms of L. cylindrica Say). The New World species are diagnosed and a key to species is provided. The male and female terminalia of Loxocera are described in detail for the first time, and their functional morphology is discussed. Eggs of most species are described and a key to the known eggs of Loxocera is provided. A phylogenetic framework for the Holarctic subgenera and species groups of Loxocera is developed based on morphological characters of the adult flies. The Old World subgenus Platystyla Macquart is synonymized with Loxocera s. str., and Imantimyia Frey is reinstated as a valid subgenus including all Holarctic species previously placed in Loxocera s. str. except the L. aristata species group. This leads to the following new subgeneric combinations: L. (L.) malaisei Frey comb. n., L. (L.) matsumurai Iwasa comb. n., L. (L.) monstrata Iwasa, comb. n., and L. (L.) omei Shatalkin comb. n. The species groups of Imantimyia are redefined, i.e. the L. achaeta-group (7 spp.), the L. fulviventris-group (4 spp.), and the L. albiseta-group (1 sp.). The Oriental subgenus Asiopsila Shatalkin is referred to Psila Meigen s. l. as a subgenus based on characters of the egg, resulting in fourteen new generic combinations: Psila (Asiopsila) brevibuccata (Shatalkin) comb. n., P. (A.) burmanica (Frey) comb. n., P. (A.) decorata (de Meijere) comb. n., P. (A.) derivata (Shatalkin) comb. n., P. (A.) formosana (Hennig) comb. n., P. (A.) freidbergi (Shatalkin) comb. n., P. (A.) humeralis (de Meijere) comb. n., P. (A.) kambaitensis (Frey) comb. n., P. (A.) limpida (Shatalkin) comb. n., P. (A.) maculipennis (Hendel) comb. n., P. (A.) michelseni (Shatalkin) comb. n., P. (A.) pleuralis (Frey) comb. n., P. (A.) primigena (Shatalkin) comb. n., and P. (A.) vittipleura (Shatalkin) comb. n.


INTRODUCTION
The Psilinae genus Loxocera Meigen, 1803 currently includes 61 described species, most of which (56 spp.) occur in the Old World.Previous authors have divided the genus into four subgenera: the Nearctic and Old World Loxocera s. str.(38 spp.), the Palaearctic and Oriental Platystyla Macquart, 1835 (5 spp.), the east Palaearctic Tropeopsila Shatalkin, 1983 (2 spp.), and the Oriental Asiopsila Shatalkin, 1998 (14 spp.) (2 Oriental species are unplaced to subgenus and might not belong in Loxocera, see Shatalkin, 1998).The subgenus Asiopsila was erected for a distinct clade of Oriental species (Shatalkin, 1998), but Shatalkin (l. c.) expressed doubts about its placement in Loxocera s. l.An additional subgenus, Imantimyia, was proposed by Frey (1925) for species related to the European L. albiseta (Schrank, 1803) but the subgenus was considered a synonym of Loxocera s. str.by subsequent authors.Three species currently placed in the Afrotropical genus Loxocerosoma Verbeke, 1968, probably belong in Loxocera.
The Nearctic species of Loxocera were first revised by Johnson (1920), who recognised three species (L.cylindrica Say, 1823 (Fig. 1), L. collaris Loew, 1869 and L. fumipennis Coquillett, 1901) and four colour varieties of L. cylindrica.Shortly thereafter Melander (1920) added a new species from the western US (L.microps).The most recent taxonomic paper on New World Loxocera is Capelle's (1953) revision, in which one more species was described (L.californica).We here redefine Loxocera, review its subgenera and species groups, and revise the New World species of the genus with the addition of a first Neotropical Loxocera and a new northeastern Nearctic species.Descriptions of the eggs of New World species and of exemplars of most Old World species groups/subgenera are also provided, including a key to all known eggs of Loxocera s. l.

Preparation methods
Male and female abdomens were cleared in hot 10% KOH, neutralized in glacial acetic acid and stored in glycerine.All eggs described in this paper were obtained by dissection from gravid females (museum specimens).Females usually contain mature eggs, providing an easily accessible additional character set for taxonomic and/or phylogenetic analyses.The eggs of Psilidae offer useful specific characters as well as characters of great phylogenetic value at the generic level.We therefore suggest that it should be standard procedure to include descriptions of eggs when describing new taxa in this family.

Photography
Photographs of museum specimens (17)(18)(19)(20) were taken with a Microptics Digital Lab XLT imaging system using a Canon EOS 1 Ds camera and Microptics ML-1000 flash fibre optic illumination system.Each image was assembled from a series of photographs (with different focal planes) using the computer freeware CombineZ, version 4.6 (Hadley, 2004).
Sister group.The most recent discussion of the phylogenetic relationships of Loxocera was presented by Shatalkin (1998).In Fig. 2 his written description of Psilinae phylogeny is translated into a cladogram and compared to our own phylogenetic hypothesis (see below).Both hypotheses agree in regarding Psila Meigen, 1803 s. l. as the sister group of Loxocera s. l. (for the monophyly of Psila s. l. see Buck & Marshall, 2006).However, Shatalkin (1998) excluded Pseudopsila Johnson, 1920 from Psila s. l., leading to a very different groundplan for Psila s. l. and the Psilinae, and resulting in Fig. 1.Loxocera (Imantimyia) cylindrica male perched on leaf (Canada, Ontario).different polarities for certain characters of phylogenetic importance within Loxocera.In a separate paper (Buck & Marshall, 2006) we clarify the identity of Pseudopsila, confirm its placement in Psila s. l. and redefine Psila s. l. based on egg morphology.Characters used in the phylogenetic analysis of subgenera and species groups of Loxocera are polarized through outgroup comparison with Psila s. l. and Chyliza Fallén, 1820 (the putative sister group of Psilinae, see Shatalkin, 2002).
preted this character as "probably plesiomorphic" without providing any explanation, we consider it a defining character of Loxocera.No further apomorphies for this clade were found.Loxocera in this original sense has been divided into two subgenera (treated as genera by Frey, 1925): Platystyla and Loxocera s. str.For reasons explained below, the subgeneric limits are redefined here and Imantimyia (previously treated as a synonym of Loxocera s. str.) is recognised as the sister group of Loxocera s. str.Shatalkin (1989) added Tropeopsila as a third subgenus to Loxocera, after previously describing it as a separate genus (Shatalkin, 1983).Tropeopsila shares with Loxocera s. str.and Imantimyia the modified, coriaceous, laterally compressed ovipositor and moderately elongate first flagellomere but lacks the femoral patch of felt-like microtomentum.The modified ovipositor is a putative synapomorphy for Tropeopsila + (Imantimyia + Loxocera s. str.).However, Psilosoma Zetterstedt, 1860, which is currently considered a subgenus of Psila (e.g., Iwasa, 1998), shows a similar ovipositor morphology, and the relationships of this group require further study.Traditionally, elongate antennae have been considered an autapomorphy of Loxocera, as well, but this character also occurs in several subgenera of Psila, i.e.Freyopsila Shatalkin, 1986(see Shatalkin, 1998), Asiopsila (see below), Psila s. str.and Xenopsila Buck, 2006(Buck & Marshall, 2006), and it is possible that elongate antennae are part of the ground plan of the Psilinae.Without access to material of Tropeopsila we are unable to further clarify its relationships.
Diagnosis.Loxocera s. l. in the present redefined sense is diagnosed as follows: face more or less receding (as typical for the subfamily) ; first flagellomere long, at least 5.5× as long as broad (high) , if shorter (most Loxocera s. str.) then arista removed from base of first flagellomere (Fig. 3), inserted in distal half or slightly before middle of flagellomere; posterior half of anepisternum with a patch of dense, downcurved hair ventrally (Fig. 19: hp) (poorly developed in some species); laterotergite slightly convex (as typical for the subfamily), not protruding; hind femur usually with preapical patch of very dense, felt-like microtomentum on lower surface; female terminalia laterally compressed and coriaceous.

Morphology and function of male and female terminalia
The male and female terminalia of Loxocera have never been described in detail, although Capelle (1953) illustrated postgonites of the Nearctic species, Griffiths (1972) provided a brief description of the male genitalia of Psilidae (including brief references to L. cylindrica), and Shatalkin (1989Shatalkin ( , 1998) ) discussed certain features of the male genitalia providing simple illustrations for most subgenera.Even recent species descriptions include little if any information on the male and female genitalia (Iwasa, 1992(Iwasa, , 1993(Iwasa, , 1996;;Shatalkin, 1998).As the following phylogenetic reassessment of the subgenera of Loxocera relies heavily on genitalic characters it is necessary to provide a detailed generic description.
The following description of the male and female terminalia and their function apply only to the subgenera Loxocera s. str.and Imantimyia (Tropeopsila was not available for examination).Notes on Loxocera s. str.are based on the European species L. hoffmannseggi Meigen, 1826, L. aristata andL. maculata Rondani, 1876; notes on Imantimyia are mainly based on the New World species and on the European L. albiseta.
Function.The different morphologies described here reflect different functional mechanisms of the male genitalia.The moveability of certain parts of the genitalia can either be observed directly or through comparison of specimens of the same species that died with their genitalia in different functional positions.
Discussion of morphology.The small pits that occur behind tergite 7 in most Imantimyia have not been described before in Psilidae.Their function is unknown.A similar structure is present in at least two undescribed species of Psila s. str.from northern Quebec and New Mexico (Buck, unpublished), but in these species the pits are much larger and more conspicuous than in Loxocera.
Discussion of function.The oviposition behaviour of Loxocera has never been observed.Based on its very compressed shape the Loxocera ovipositor was thought to be adapted for piercing tissue of the host plant (Steyskal, 1987;Iwasa, 1998).Examination of the fine structure does not support this hypothesis.The cerci or the fused tergite 10 + cerci bear several longer hairs dorsally and ventrally, some of which are directed more or less posteriorly (e.g., Figs 53,65).These hairs would hinder penetration of the plant tissue and would probably break off at the first oviposition attempt.In contrast to the piercing ovipositors of Agromyzidae and Tephritidae, the ovipositor of Loxocera does not possess any raspers or sharp edges enabling it to cut into plant tissue.It seems more likely that the ovipositor is adapted for inserting eggs into narrow crevices.Based on existing knowledge of the host plants of Loxocera (see below) this could be the space between leaf sheaths and stems of Carex or Juncus.

Biology
All members of the family Psilidae appear to be phytophagous (Steyskal, 1987), though host plants of most species are unknown.The most common eastern Nearctic species of Loxocera, L. cylindrica, breeds in stems of the sedge Carex interior Bailey (Valley et al., 1969), and apparently attacks healthy plants.The European L. albiseta was reared from stems of Juncus effusus L. (de Meijere, 1941).Immature stages are largely unknown except for the two European species L. albiseta (larva: de Meijere, 1945;puparium: de Meijere, 1941) and L. aristata (egg: see Taxonomic treatment of eggs below).
Monophyly.Loxocera s. str. in the traditional sense (e.g., Hennig, 1941) excluded species with an elongated scape and pedicel (L.hoffmannseggi, L. malaisei), which were placed in a separate subgenus Platystyla.Iwasa (1992Iwasa ( , 1998) ) slightly modified the concept of Platystyla after discovering species with a short scape and pedicel, emphasizing the more distal insertion and thickening of the arista in this subgenus.Frey (1925) was the first author to realize that L. (L.) aristata (the type species of Loxocera) and its relatives are not closely related to the remaining species of Loxocera s. str.: He elevated Platystyla and Loxocera s. str. to genus rank and created a new subgenus Imantimyia for the species of Loxocera s. str.outside the L. aristata-group.His classification was not adopted by subsequent authors, and Imantimyia has since been treated as a synonym of Loxocera s. str.(e.g., Hennig, 1941;Soós, 1984).Shatalkin (1998) confirmed L. aristata plus related species as a distinct species group within Loxocera s. str.but continued to use the traditional subgeneric classification.None of the previous workers realized that Platystyla is closely related to the L. (L.) aristata-group, and that both together form a wellcharacterized monophyletic group.In combining the two groups the name Loxocera retains priority over Platystyla and is hereby instated as the valid name for the clade.The sister group, Frey's Imantimyia, includes the remainder of the species of the previous Loxocera s. str.The characters used by Frey (1925) to define Imantimyia are ambiguous and unsuitable but the monophyly of this subgenus is demonstrated by other characters (see below).
Groundplan.The hypothesized groundplan characters of Loxocera s. str.are listed below (based on examination of the European species L. hoffmannseggi, L. aristata and L. maculata).The corresponding character states found in the sister group Imantimyia are given in parentheses.
Characters of uncertain polarity (character states of Imantimyia in parentheses): (17) Hypandrial bridge present: Fig. 7: hb.According to drawings provided by Iwasa (1993) the hypandrial bridge might be medially interrupted in L. monstrata and L. matsumurai (hypandrial bridge absent).( 18 Discussion.The monophyly of Loxocera s. str. is well supported by a large number of unique autapomorphies.Only characters ( 6) and ( 9) occur elsewhere in the Psilinae (i.e., in Psila, subgenus Xenopsila), where they have developed independently (Buck & Marshall, 2006).The monophyly of Imantimyia on the other hand is less strongly supported.The most convincing autapomorphy is the fusion of the cerci with tergite 10 in the female (character 16).The remaining defining characters appear to be prone to homoplasy to at least some degree: The reduction of the pregenital sclerite (character 14) is a widespread condition in Psilidae, and Loxocera s. str.appears to be the only group in the whole family that has preserved a well-developed, setulose pregenital sclerite (tergite 7).Its reduction must therefore have taken place at least three times independently within the family.Two character states of unknown polarity also invite comment: A hypandrial bridge (character 17) is present in Loxocera s. str., Chyliza and apparently in Tropeopsila (Shatalkin, 1998: Fig. 4), and must have been independently lost or gained more than once in the evolution of Psilidae.The transverse phallapodeme (character 18) of Loxocera s. str. is shared with Psilosoma and Psila dimidiata Loew, 1869, where it must have developed independently.The oblong phallus (character 16) of Loxocera s. str.appears to be similar to Tropeopsila (Shatalkin, 1998:  Species groups.Loxocera was first divided into species groups by Shatalkin (1998), who recognised four groups, two of which (L. achaeta-and L. fulviventris-group) are now placed in Imantimyia.The taxonomic limits of both groups are corrected and their definitions are based on a more stringent character analysis.The European L. albiseta, which was placed in the L. fulviventris-group by Shatalkin, is removed from this group based on the phylogenetic analysis presented below.It is treated separately here as the only member of the L. albiseta-group.The L. fulviventris-group in the revised sense is quite homogeneous and consists of morphologically similar species.This is also true for the L. achaeta-group if the somewhat aberrant Central American species L. ignyodactyla sp.n. is excluded.In the present phylogenetic analysis we include the following four operational taxonomic units: L. achaeta-group s. str.(excl.L. ignyodactyla sp.n.), L. ignyodactyla sp.n., L. fulviventris-group, and L. albiseta.Loxocera algerica Villeneuve, 1913, L. chinensis Iwasa, 1996and L. triplagata Wang & Yang, 1996 were not available for examination, and their group affiliation remains unknown.
Monophyly.The monophyly of the L. acheata-group in the strict sense (excl.L. ignyodactyla sp.n.) is established by four apomorphic characters (plesiomorphic character states in parentheses): (A1) Inner space of
Discussion.The data support two equally most parsimonious cladograms (Fig. 16) that differ with regard to the position of L. albiseta.Cladogram 1 with L. albiseta as the sister group of the remaining Imantimyia species seems slightly more likely than cladogram 2 with this species as the sister species of the L. achaeta-group.Shatalkin (1998) 1. Psila s. l.; ordered by decreasing degree of relatedness), all of which have apically or preapically inserted postgonites.Basally inserted postgonites do occur in derived subgroups of Psila s. l., but these are clearly cases of convergence (Buck & Marshall, 2006).
The sister group relationship between the Neotropical L. ignyodactyla sp.n. and the Holarctic remainder of the L. achaeta species group is strongly supported by characters 3, 4, 7, 9 and 10, especially by the basal insertion of the postgonites (character 7).It is noteworthy that the loss of peg-like sensilla (character 10) has occurred independently in Loxocera s. str.(see above).

Taxonomic treatment: adults Key to adults of the New World species of Loxocera
Note: All New World species of Loxocera belong to the subgenus Imantimyia.
Discussion of synonymy.Like other species in the genus, L. collaris is quite variable, especially in coloration, genal width, length of antenna, shape of postgonite and development of the phallapodeme.Capelle (1953), who examined only one male of L. collaris when describing his new species L. californica, was obviously unaware of this variability.After studying long series of L. collaris from various localities and additional material of "californica" from Mexico it became clear that the latter is just a variety of the former.The length of the ocellar bristles especially the vertical bristles, which were Capelle's main diagnostic characters, and also the eye height is less on average in western specimens but eastern specimens sometimes also have shorter bristles.The darker coloration of the thorax and abdomen of "californica" might be climatically induced because all available specimens are from higher elevations.Specimens from comparable elevations in the east (Tennessee: Great Smoky Mts) show the same dark body pattern as described for "californica".No difference between eastern and western specimens was found in other diagnostic characters used by Capelle (1953) like the length of first flagellomere, body size, length of body hair, head shape and shape of postgonite.The latter varies considerably in size and curvature of the posterior spine even among specimens from the same locality (e.g., Figs 27, 28).The unusual shape of the basal portion of the postgonite in "californica" as depicted in Capelle's Fig. 7 was not confirmed by examination of the holotype (Fig. 26).No differences were found between the eggs of eastern and Mexican specimens (eggs from specimens from the western US were not available).

Loxocera microps
Variation.The coloration of this species is extremely variable.Southern specimens (incl.the paratype, Fig. 18) and a male from Willow, Alaska are predominantly ochreous with largely brown abdomen, restricted dark brown markings on the mesoscutum, dark brown ocellar tubercle, and usually some infuscation of the frons, lower portion of katepisternum and postnotum.On the contrary, specimens from the Yukon Territory, and Unalakleet, Alaska, are almost completely blackish brown excluding anterior margin of frons narrowly, lateral portions of face, lower eye margin, anterior vertical stripe of gena, anterior face of all coxae, knees, tibiae distally, and tarsi.An unusual character for Psilidae is the presence of a few setulae on the meron of some specimens.The unusual shape of the postgonite illustrated by Capelle (1953: Plate  2, Fig. 8) (reproduced in Fig. 38) is probably due to distortion of the specimen and/or inaccurate illustration.The postgonite of the paratype (with identical collection data as holotype) is depicted in Figs 36, 37.

Loxocera cylindrica Say, 1823
Taxonomy.The type of L. cylindrica is destroyed and Say's (1823) description is inadequate to distinguish this species from the very similar L. ojibwayensis sp.n. (described below).Considering that the new species is rare and only known from the type locality but L. cylindrica (in the interpretation of previous authors) is common and widespread, we continue to apply this name to the common species, i.e. we are using it as a senior synonym of L. pleuritica, L. pectoralis and L. obsoleta.Lectotypes of the latter two are designated to clarify the identity of these nominal species with regard to L. ojibwayensis sp.n.

Loxocera fumipennis
Distribution.Prairie provinces of Canada and American midwest south to Texas and Arizona (Shewell, 1965).This species replaces L. cylindrica in the mid-west; the ranges of both species narrowly overlap along the eastern limit of L. fumipennis.
Head (Fig. 19).Frons not or hardly projecting beyond level of anterior eye margin, slightly transversely depressed at level of anterior third of eye.Frontal orbits silvery microtomentose in anterior half, with a row of about 10 hairs, fronto-orbital bristle not differentiated.Frontal vitta sparsely setulose in anterior half, especially near anterior margin.Ocellar triangle slightly depressed along midline, with slightly convex lateral margins, extending anteriorly about 0.85× length of frons.Ocellar bristles relatively short, length 2.0-2.5×ocellar diameter.Postvertical bristles not differentiated, 2-6 postocellar hairs present.Vertical bristles short; outer vertical bristle slightly longer than inner vertical, ca.3× as long as ocellar diameter.Face moderately slanting, below antennae in upper half with slightly elevated midline.Upper half of face with inconspicuous brownish microtomentum, lower half with more distinct silvery microtomentum, the two halves reflecting light at different angles.Microtomentum of lower face interrupted by median, triangular (dorsally tapered), bare, shining area.Parafacials narrow, at narrowest point barely as wide as swollen base of arista, with a row of setulae and with distinct silvery microtomentum.Gena with several setulae ventrally, disc very sparsely setulose, lacking silvery microtomentum.Eye large, protuberant; dorsal eye margin about level with most elevated parts of frons.Eye height 4.3-7.6×genal height.Scape slightly longer than broad (dorsal view), its length equal to maximum width of first flagellomere, with several setulae near dorsoapical margin, otherwise bare.Pedicel 1.3× as long as scape, with distinct dorsal seam, setulose.First flagellomere very long, twice as long as face, more or less parallelsided in lateral view, base hardly widened.Arista inserted close to base of first flagellomere, basal margin of socket at same level as ventroapical margin of pedicel; length of arista ca.0.7× length of first flagellomere, with swollen basal fourth.Pubescence of swollen basal portion short, shorter than maximum diameter of arista; pubescence of slender apical portion long, longest rays twice as long as maximum diameter of arista.Palpus with scattered brownish to blackish setulae on outer and ventral surface, without outstanding bristles.

208
Thorax with the usual complement of bristles.Notopleural bristle poorly differentiated, brownish (not black), not much longer than surrounding hairs.Supraalar and postalar bristle well developed, always black.One prescutellar pair of dorsocentral bristles, brown to black, as long as supra-alar and postalar bristle or slightly shorter.Scutum bare anteriorly to level of posterior margin of postpronotal lobe.Hairs of scutum short, pale brown, denser along dorsocentral lines, slightly sparser between, much sparser lateral of dorsocentral lines, denser on notopleuron.Sculpture of scutum associated with density of hairing, stronger in areas that are more densely haired, smooth in bare areas.Postpronotal lobes smooth, hairs sparse, sometimes reduced to a few setulae.Scutellum with finely wrinkled disc, apical bristles ca.0.8-1.0×as long as scutellum, preapical pair smaller, 0.4-0.6×as long as apical pair, absent in half of the specimens examined.Pleuron mostly smooth and shining; propleuron with dense, felt-like microtomentum along lower and posterior margin; posterior portion of laterotergite and lateral portions of mediotergite with sparser microtomentum.Anepisternum in posterior 3/5 with short, moderately dense, upcurved brownish hair, ventrally with the usual patch of dense, pale, downcurved hair.Katepisternum with brownish hair, ventrally relatively dense and pale, dorsally sparser, central portion almost bare.Posterior spiracle with numerous long setulae along margin.
Legs haired except bare posteroventral surface of fore femur and largely bare lower surface of mid femur.Hind femur of male without ventral process.Mid tibia with one long and (1-)2 shorter ventroapical bristles, blackish or reddish except long bristle, which is black.Hind tibia with moderately developed, blackish or reddish, anteroventral, apical bristle.Hairing of tarsi becoming darker towards apex, distinctly darkened in apical 2-3 tarsomeres.Wing as in Fig. 54, membrane slightly tinged with brown, pattern somewhat variable: apical fifth of wing infuscated, sometimes just barely extending into cells r1 anteriorly and m posteriorly, infuscation sometimes interrupted medially in cells r2+3 and r4+5.Area around posterior crossvein, last sector of CuA1 and penultimate sector of M (between crossveins) also infuscated, rarely area around last sector of M infuscated, as well, connecting apical spot with darkening around posterior crossvein.Wing veins brown in dorsal view excluding most of costa, subcosta, stem vein, R1 and Rs, which are yellowish brown.Last sector of vein M with moderately strong curvature.
Male terminalia very similar to L. cylindrica except postgonites.Male pregenital sclerite well defined but broadly interrupted dorsally.Epandrium of holotype darkened in ventral half.Cerci setulose (Fig. 45  surface of pouch with minute aciculate sculpture in compressed middle portion (Fig. 47).Phallapodeme free anteriorly from phallic pouch (Fig. 43: pa).Setulae of phallapodemic sclerite few in number, posterior ones on a more or less developed protuberance near base of posterior arms (Fig. 44: pst).Apex of phallapodemic arms truncate (Figs 43,44: psa).Lateral surface of hypandrium with a few widely scattered setulae and a small patch of microtrichia just above postgonite (Fig. 43: ha).Postgonite sickle-shaped (Fig. 48), strongly sclerotized and mostly dark brown with black apices, medial (ventral) surface with 2-4 setulae in anterior portion, lacking microtrichia.Shape of postgonite subject to slight allometric variation: in larger specimens margin next to patch of setulae more convex than in smaller specimens.Phallus T-shaped in posterior view (Fig. 46: ph), with relatively long, membranous distal portion.
Female terminalia extremely similar to L. cylindrica; no differences of taxonomic value were detected.Intersegmental membrane between segments 6-7 almost completely sclerotized (excl.pleural portions and dorsomedial emargination), sclerotization continuous with tergite and sternite.Segment 7 laterally compressed (Fig. 49), tergite subcarinate along midline, especially in anterior half.Tergite 7 on each side with short posterior extension and a small pit below it (Fig. 50); exposed (non-retractable) portion of intersegmental membrane bare and minutely longitudinally striate in anterior 2/3 of dorsal surface, otherwise finely microtrichose, retractable portion of intersegmental membrane entirely microtrichose.Segment 8 (Figs 51-53) distinctly striate on whole surface, with scattered short setulae, completely devoid of microtrichia; posterior margin with deep, acute, medial emargination dorsally (Fig. 51), not clearly delimited laterally, and with a simple, narrowly rounded sternal lobe.Tergite 10 and cerci fused (Fig. 51: T10, ce).Tergite 10 dorsally with scattered, short setulae and one pair of bristles just basal of free apical portion of cerci.Sternite 10 with a few scattered setulae and 1-2 longer bristles, apex with a fringe of long felt-like microtrichia (Fig. 52, 53: S10).Cerci (Figs 51-53: ce) moderately flattened dorsoventrally, relatively long, clearly discernable even in undissected specimens.Each cercus bare dorsally, with a lateral row of short bristles that appear to arise from a small groove, and with a ventral row of longer bristles, two of which are enlarged.Loxocera ignyodactyla Buck sp.n. (Figs 5,20,(55)(56)(57)(58)(59)(60)(61)(62)(63)(64)(65) Description.Largest species of the subgenus and one of the largest species in the genus, body length 12 mm, wing length 8 mm, length of antenna 3 mm.Body red except: Scape, first flagellomere except extreme base, ocellar prominence and small area right behind posterior ocelli, postpronotal lobes excluding margins and anterior surface, black.Major bristles of head and thorax also black.Palpus blackish in male, hardly infuscated in female (difference probably due to individual variability, not sexual dimorphism).Pedicel on outer surface and ventrally, first flagellomere basal of arista, dark reddish.Swollen basal portion of arista reddish yellow, becoming white distally.Face and gena slightly yellowish red.Haltere yellowish.
Head (Figs 5,20).Frons strongly projecting beyond level of anterior eye margin (much more than in Nearctic species), slightly transversely depressed at level of anterior third of eye.Frontal orbits with a row of about 15 hairs, last hair enlarged, ca.twice as long as previous ones, forming a small fronto-orbital bristle.Frontal vitta sparsely setulose in anterior half, especially near anterior margin.Ocellar triangle slender and very pointed, with slightly concave lateral margins, extending anteriorly about halfway between level of anterior margin of eye and anterior margin of frons.Ocellar bristles moderately developed, length ca.3× ocellar diameter.Postvertical bristles not differentiated, 3-7 postocellar hairs present.Vertical bristles relatively short; inner vertical bristle slightly longer than outer vertical, ca.4× as long as ocellar diameter.Face strongly slanting, with short, delicate median carina at level of antennal base and slightly below.Parafacials narrow, at narrowest point barely as wide as swollen base of arista, with a row of setulae and  with weak silvery microtomentum.Gena swollen, with several stronger setulae ventrally, disc very sparsely setulose, lacking silvery microtomentum.Eye large, protuberant; dorsal eye margin projecting slightly above level of frons.Eye height 3.3-3.4×genal height.Scape slightly longer than broad (dorsal view), its length equal to maximum width of first flagellomere, with several setulae near dorsoapical margin, otherwise bare.Pedicel slightly longer than scape, with distinct dorsal seam, setulose.First flagellomere very long, twice as long as face, its diameter slightly increasing towards apex (lateral view), base hardly widened.Arista inserted close to base of first flagellomere, basal margin of socket removed from (level of) ventroapical margin of pedicel by 1.0-1.5×ocellar diameter; length of arista ca.0.8× length of first flagellomere, with swollen basal fourth.Pubescence of swollen basal portion short, shorter than maximum diameter of arista; pubescence of slender apical portion long, longest rays twice as long as maximum diameter of arista.Palpus with scattered blackish setulae on outer and ventral surface, without outstanding bristles.
Thorax with the usual complement of bristles.Notopleural bristle slightly over half as long as the supraalar and postalar bristle.One prescutellar pair of dorsocentral bristles, 1.3-1.4×as long as supra-alar and postalar bristles.Scutum with rough surface sculpture in haired region, smooth in bare anterior region.Scutum bare up to level of anterior third of postpronotal lobe, otherwise uniformly setulose.Hairing of scutum short and dense, mostly black, reddish in notopleural region, not arranged in rows.Postpronotal lobes smooth, hairing much sparser than on scutum.Scutellum with finely wrinkled disc, apical bristles ca.1.4× as long as scutellum, preapical pair small, only ca.0.3× as long as apical pair.Pleuron mostly smooth and shining; propleuron with dense, felt-like microtomentum along lower and posterior margin; posterior portion of laterotergite and lateral portions of mediotergite with sparser microtomentum.Anepisternum posteriorly and dorsally with short, moderately dense, upcurved reddish hair, in posteroventral corner with the usual patch of dense, pale, downcurved hair.Katepisternum with reddish hair, ventrally relatively dense, dorsally sparser, central portion almost bare.Posterior spiracle with numerous long setulae along margin.
Legs more or less uniformly haired except bare posteroventral surface of fore femur and largely bare lower surface of mid femur.Hind femur of male with distinct posteroventral process before middle (Fig. 56).Mid tibia with one long and 2-3 shorter ventroapical bristles, mostly reddish except long bristle, which is black in one of the two specimens.Hind tibia with moderately developed, reddish, anteroventral apical bristle.Hairing of tarsi becoming darker towards apex, distinctly darkened in apical three tarsomeres.Wing (Fig. 55) distinctly yellowish, with moderately developed dark band at level of posterior crossvein; band more or less interrupted along centre of cells r2+3, r4+5 and dm.Wing veins mostly yellowish, brown in banded part of wing.Last sector of vein M with unusually strong curvature.
Preabdomen slender.Syntergite 1+2 ca.twice as long as broad (ratio influenced by shrinkage from drying), laterally with conspicuously enlarged bristles in apical halves of segments 1 and 2, on latter almost erect and nearly as long as width of segment at level of insertion (in air-dried specimens).Abdominal tergites smooth, with very fine, evenly spaced, transverse wrinkles; tergite 1 hardly with coarser sculpture.
Etymology.The name is a latinized compound Greek adjective and refers to the finger-like ventral process of the male hind femur (Gr.ignya: part of leg behind thigh and knee, ham; Gr. daktylos: finger).
Distribution.Only known from Puntarenas Province in Costa Rica at elevations around 2000 m.
Relationships.Despite significant differences this species is best placed within the mainly Holarctic L. achaetagroup (see phylogeny of Imantimyia above).It preserves several plesiomorphic features that have been lost in the Holarctic species (see phylogenetic analysis of Imantimyia species groups above) and represents the most basal member of its group.

Taxonomic treatment: eggs
In order to allow comparisons between all available subgenera and species groups of Loxocera, three species representing Old World-restricted groups were included in the following treatment: L. (L.) hoffmannseggi, L. (L.) aristata, L. (Imantimyia) albiseta.Besides describing the eggs of Loxocera, we include a description and discussion of the egg of Psila (Asiopsila) decorata, justifying the removal of Asiopsila from Loxocera (see above).
Generic diagnosis (based on the species included in the key below).Eggs roughly cylindrical, sometimes very slightly curved or with straight lower (?) and arched upper (?) surface, length 0.95-2.3mm, width 0.20-0.33mm, slightly tapered towards both ends, which are rounded or narrowly truncate; micropylar end always more obtuse or more broadly truncate than posterior end.Chorion with very finely to very coarsely granular texture.Surface either with linear polygonal reticulation or with fine, close-set, longitudinal ridges connected by variably developed transverse ridges or with a combination of both.Surface in some species partially plain (without reticulation or ridging).Texture of chorion usually becoming coarser at both poles, appearing microporose or microreticulate, increasing in size to small or large pores.Micropyle located in centre of poorly to sharply defined, flat to deeply depressed, central area, which is of finer texture than surrounding area.

Key to known eggs of Loxocera s. l.
Note: For a key to Psilidae genera see Buck (in press).
1 Reticulation of egg surface coarse (Figs 73,76,77,85)  with small, even truncation.Chorion relatively thick, with very fine, uniform, granular texture.Entire surface reticulated with rows of somewhat irregular polygons (Fig. 73); polygons becoming shorter near poles, especially near posterior pole; polygons with 0-1(-2) very faint, circular spots of slightly coarser granular texture; rows of polygons numbering ca.70 across circumference at level of greatest diameter.Reticulation slightly raised above surface level (surface not distinctly ridged).Micropylar truncation (Fig. 71) with scattered, roughly circular pores (aeropyles?) separated by smooth interspaces; central area around micropyle lacking pores.Posterior truncation also with pores, but pores separated by mostly very small, ridge-like interspaces and present in central area, as well.
Loxocera (Imantimyia) collaris Loew, 1869 (L.fulviventris-group)  Description.Egg (Fig. 75) about as long as abdominal segments 3-4 combined (length 0.95-1.00mm, width ca.0.20 mm); micropylar pole more obtusely rounded than posterior pole.Surface covered with fine, close-set, longitudinal ridges that are connected by short, very faintly indicated, transverse ridges (Fig. 76); transverse ridges more prominent near poles, especially near micropylar pole.Number of ridges totalling ca.55 across circumference at level of greatest diameter.Chorion with extremely fine, granular texture between ridges; ridges itself fairly coarsely granular.Both poles completely occupied by large pores that are separated by thin lamellar ridges, size of pores not increasing toward centre; micropyle in small circular depression in centre of micropylar pole (Fig. 74).
Loxocera (Imantimyia) microps Melander, 1920 (L.fulviventris-group) (Fig. 77) Description.Egg about as long as abdominal segments 3-4 combined (length ca.1.1 mm, width ca.0.20 mm); micropylar pole more obtusely rounded than posterior pole.Entire surface reticulated with somewhat irregular polygons that are not arranged in distinct rows (Fig. 77); polygons becoming shorter near poles; number of polygons totalling ca.55 across circumference at level of greatest diameter; reticulation slightly raised above surface.Chorion with extremely fine, granular texture between ridges; slightly coarser on ridges, with a larger spot at each intersection; centre of each polygon with (0-)1-2 circular to elliptic, slightly coarser granular areas.Micropylar pole and posterior pole similar to L. collaris but pores slightly smaller.Description.Egg (Fig. 80) long and slender, slightly longer than abdominal segments 3-5 combined (length 1.45-1.55mm, width ca.0.20 mm), very slightly curved or with straight lower (?) and arched upper (?) surface; micropylar pole narrowly subtruncate, posterior pole rounded.Concave (lower?) surface coarsely granular, lacking reticulation; arched (upper?) surface with very faint polygonal reticulation, granulation very coarse, appearing microporose, diameter of "micropores" greater than lines delimiting polygons.Surface on two opposite sides with narrow band of distinct, linear, somewhat irregular polygonal reticulation (each band only 3-4 polygons wide) (Fig. 78), third side with similar but fainter reticulation, fourth side almost plain, with extremely faint reticulation; polygons shorter near poles.Micropylar pole (Fig. 79) with very coarse irregular, dense granulation; central area surrounded by a slightly irregular ring of 10-12 small, ill-defined pore-like structures (aeropyles?); central area well defined, circular, smooth, bearing micropyle in centre.Posterior pole coarsely granular, appearing microporose.Description.Egg (Fig. 88) long and slender, as long as abdominal segments 3-5 combined (length ca.1.6 mm, width ca.0.25 mm); micropylar pole with small truncation, posterior pole narrowly rounded.Chorion with very fine, uniform, granular texture.Surface (excluding ventral side) covered with fine, close-set, longitudinal ridges connected by very short, narrow, transverse ridges (Fig. 85).Lower surface finely reticulated with somewhat irregular, elongate (mostly hexagonal) polygons (Fig. 86), which become gradually less elongate at both poles; reticulation not raised above surface level.Number of rows of polygons on lower surface plus number of ridges of remaining surface totalling ca.85 across circumference at level of greatest diameter.Micropylar pole (Fig. 87) with close-set pores of variable size (mostly large), except in central area, which is depressed and bears micropyle in centre.Posterior pole coarsely granular with small close-set pores in centre.
Material examined.Canada: two eggs from female paratype debu01117472 (full data above).
Material examined.Costa Rica: two eggs from female paratype (full data above).

Discussion
Morphology.The only previously described Loxocera egg is that of L. aristata (Gaponov, 1999).Gaponov's description diverges radically from the L. aristata eggs studied by us, and is obviously based on a different species.His eggs are smaller than any of our species, and are in fact only slightly more than half as long as the examined L. aristata eggs from Sweden.Gaponov's SEM micrographs show strong longitudinal ridging connected by small transverse ridges, while our specimens have a completely smooth surface partially covered by linear (not raised), polygonal reticulation.The small size of the eggs and the surface sculpture is consistent with species of the L. fulviventris-group, perhaps pertaining to one of the Palaearctic species L. fulviventris and L. sylvatica.We are also convinced that the two, highly unusual, prominent, circular ridges of the upper surface of the egg described by Gaponov (1999) are due to a preparation artefact.None of the species studied here shows any indication of circular ridging of the egg surface.
Phylogeny.Few characters of phylogenetic significance at the subgenus and species group level were found.Some of the differences that appear to be consistent for certain species groups might turn out to be unreliable when further species from other biogeographic regions are examined.The observed character states are difficult to polarize because eggs of the sister group of Loxocera (Psila s. l.) and the next outgroup (Chyliza) are very different (see below, and Buck & Marshall, 2006).The following tentative conclusions can be drawn: Eggs of the two examined species of Loxocera s. str.are quite different and do not show any obvious synapomorphies.The most striking egg within the subgenus Imantimyia is that of L. albiseta, which possesses a unique micropylar area.This might be considered another autapomorphic character for the L. albiseta-group.Species of the L. fulviventris-group have eggs that are more strongly ridged than in other species and possess very large and uniformly sized pores at the micropylar pole.The latter character is probably apomorphic for the species group.Within the L. achaeta-group the Neotropical L. ignyodactyla sp.n. stands out in egg characters as it does in adult characters.The egg is most significantly characterized by the very weakly sculptured posterior pole.As a whole, the group is difficult to define based on egg morphology.Remarkably, characters like the strength (elevation) of the ridging of the egg surface and the toughness of the chorion vary widely within certain groups, indicating a high degree of homoplasy.Psila (Asiopsila) decorata (de Meijere, 1914)  Description.Egg (Fig. 89) elliptical, ca.0.65× as long as abdominal segments 3 and 4 combined (length ca.0.55 mm, width ca.0.15 mm); micropylar pole with small, circular, disk-like elevation (Fig. 90), posterior pole rounded.Egg surface in mid section with ca.24 broad, longitudinal, rounded (cross section approximately semicircular) ridges (Fig. 92: clr) around its circumference connected in regular intervals by narrower transverse ridges (Fig. 92: ctr); number of longitudinal ridges decreasing toward poles through anastomoses; at micropylar pole number of ridges equalling number of aeropyles on micropylar elevation; each ridge terminating at an interspace between base of two aeropyles.Both longi-tudinal and transverse ridges with irregular reticulation (reticulation located on inner surface of chorionic air canals; see Hinton, 1981: Plate 123 E, F).Areas between the ridges roughly circular, unreticulated, with small patches of more granular texture.Micropylar elevation (Fig. 91) flat, bearing ten large, circular aeropyles (Fig. 90: ae) around circumference.Micropyle tiny, located exactly in centre of disk-like process.Posterior pole without specialized structures, bearing same reticulation as on longitudinal and transverse ridges.
The most important difference between eggs of Loxocera and Psila is the presence of a peculiar disk-like, micropylar cap with a corona of ca.9-10 aeropyles in the latter.In Loxocera the micropylar pole is tapered and not developed as a clearly delimited cap; the micropylar aeropyles are distributed in an irregular pattern and are usually much smaller.Apart from the micropylar differences, the longitudinal ridges of the general surface (if present) 217 are much more numerous, very narrow (not broad and rounded) and do not possess wide, internally reticulated air canals as in Psila.

OUTLOOK
The present study provides a phylogenetic framework for most of the Holarctic subgenera and species groups of Loxocera.The following topics require further study: (1) Phylogenetic position of Tropeopsila.Critical to solving this question is egg morphology, which will clarify whether this subgenus belongs in Psila s. l. or Loxocera.
(2) Species groups of Loxocera s. str.This Palaearctic/Oriental subgenus was not organized into species groups because only three species were available for examination.Antennal morphology varies widely within the subgenus, and it will be interesting to determine whether external characters are consistent with phylogeny derived from genitalic characters.(3) Relationships of African Loxocera.According to Shatalkin (1998) the African Loxocera species form a monophyletic group.Their subgeneric placement (in Imantimyia or Loxocera s. str.) and relationships with other species groups has yet to be established.( 4) Status of Loxocerosoma.The African genus Loxocerosoma was separated from Loxocera on very tenuous grounds (Verbeke, 1968).Its three species probably possess a felt patch on the hind femur and therefore most likely belong in the clade that includes Imantimyia and Loxocera s. str.

TABLE 1 .
Character matrix for phylogenetic analysis of species groups in Imantimyia.