New genera of philopotine spider flies (Diptera, Acroceridae) with a key to living and fossil genera

Abstract Information on the three previously described species of Halocoryza Alluaud is updated and a new species for the genus from Isla Carmen, Sea of Cortés, Baja California Sur, México is described. Halocoryza whiteheadiana sp. n. was found at UV light on a beach of that island. This species does not fit the profile of the other three species, i.e., living on coralline beach sands, or in the Mangrove intertidal zone. Two alternative possibilities as to why this is so are suggested and a study plan for testing these possibilities is proposed.


Introduction
Spider flies (Diptera: Acroceridae) are a geographically cosmopolitan group although most species are relatively rarely collected. Most species feed at flowers and are likely important specialized pollinators as suggested by their frequently elongate proboscis (often equal to body length) and nectar feeding habits, although some species have reduced or even vestigial mouthparts (Schlinger 1981(Schlinger , 1987. Adults have a distinctive mor-phology and a wide diversity of form and colour, but usually with a small head, greatly enlarged lower calypter and swollen abdomen. Larvae are parasitoids of spiders, with a hypermetamorphic life cycle consisting of four instars (Schlinger 1981(Schlinger , 1987(Schlinger , 2009. Acroceridae comprise over 520 described species in about 53 genera (Pape and Thompson 2011). The species are traditionally separated in three extant subfamilies -Acrocerinae, Panopinae and Philopotinae, based on adult morphology and host specificity. Panopinae have been postulated as the most primitive and Acrocerinae the most derived, with Philopotinae supposedly occupying an intermediate position (Schlinger 1987). Phylogenetic analyses by Winterton et al. (2007) based on molecular data, however, do not corroborate this subfamilial arrangement, with Acrocerinae recovered as polyphyletic and Panopinae as a derived clade. The monophyly of Philopotinae has never been questioned based on a series of morphological synapomorphies (Schlinger 1981), a position also strongly supported by analyses of molecular data ). Adults of Philopotinae are characterized by enlarged postpronotal lobes that are usually contiguous dorsomedially to form a collar around the head, as well as varying degrees of arched body shape (Figs 1-7).
Eulonchiella eocenica Meunier, 1912 was briefly described and poorly illustrated by Meunier (1910) and(1912) from Baltic amber (only in the latter publication was the name Eulochiella eocenica applied for the first time). The holotype was deposited in the Albertus University Collection in Königsberg -Prussian territory at the time and now belonging to Russia -but was lost during the Second World War (Hennig 1966). Fortunately, Frank Hull made relatively more accurate drawings than Meunier and notes about the fossil during a visit to this collection prior to the war. Based on these unpublished data, Hennig (1966) redescribed and figured the species. Recently a specimen in the George Poinar collection, matching the original descriptions by Meunier (1910Meunier ( , 1912 and subsequent redescription and figure in Hennig (1966), has been identified as E. eocenica. This individual is also from Baltic amber deposits and is preserved in excellent condition. Herein we diagnose Eulonchiella eocenica and designate a neotype based on this newly discovered specimen. We also describe the new genera Schlingeriella irwini gen. et sp. n. from New Caledonia and Quasi fisheri gen. et sp. n. from Mexico, and provide a dichotomous key to all living and fossil genera of Philopotinae.

Materials and methods
Terminology follows McAlpine (1981) and Schlinger (1981). In most acrocerids, two crossveins span the area between the radial and medial sectors enclosing the cell r 4+5 . The proximal crossvein is r-m, while the distal crossvein bisecting cell r 4+5 (between wing veins M 1 and R 4+5 , or rarely R 5 ) is referred to here as 2r-m following Hardy (1946). Collections where specimens are deposited are as follows: Muséum National d'Histoire Naturelle, Paris, France (MNHN), California Academy of Science, San Francisco, USA (CAS), California State Collection of Arthropods, Sacramento, USA (CSCA) and Queensland Museum, Brisbane, Australia (QM). Descriptions were constructed using Lucid Builder 3.5, using a matrix database of character states, which were then exported using the natural language function into XML and a text document. Specimen images were taken at different focal points using a digital camera and subsequently combined into a serial montage image using Helicon Focus software. High-resolution digital images were deposited into Morphbank with embedded URL links within the document between descriptions and Morphbank images. All new nomenclatural acts and literature are registered in Zoobank (Pyle and Michel 2008). Eulonchiella eocenica Meunier 1912: 177 -Meunier 1910: 177, Brunetti 1926: 583, Hennig 1966: 7, Evenhuis 1994: 311. Type species: Eulonchiella eocenica Meunier, 1912: 177. Type material. Neotype male, Baltic amber (#DB 10-12) (CAS). Diagnosis. Body shape arched; colouration non-metallic brown-black; head spherical, size slightly smaller than thorax width; eye bare; male frons narrowed; eyes contiguous above and below antennal base; posterior margin of eye rounded; proboscis length greater than head length; position of antenna in middle of frons; flagellum shape stylate; palpus present; thorax with postpronotal lobes enlarged, medially contiguous to form collar; legs not greatly elongated, tibial spines absent; pulvilli present; subscutellum slightly enlarged; wing hyaline, markings absent; costa ending in radial field; costal margin straight in both sexes; humeral crossvein present; alula well developed; anal lobe not enlarged; R 2+3 present; R 4+5 present as single vein; radial veins meeting wing margin before wing apex; cell r 4+5 bisected by crossvein 2r-m, narrow elongate; discal cell present, closed apically; medial veins M 1 , M 2 and M 3 present; medial veins tapered and faint towards margin; cell m 3 absent; CuA 1 joining M 3 and petiolate, not reaching wing margin; CuA 2 fused to A 1 , not reaching wing margin, petiolate; abdomen smooth, shape rounded, cylindrical, similar width to thorax.
Comments. The above diagnosis is based on a neotype male of Eulonchiella eocenica Meunier deposited in the Poinar collection (#DB 10-12) (to be ultimately housed in CAS). Hennig (1966) discussed this monotypic genus based on drawings by Meunier (1910) and a drawing provided by Frank Hull (published in Hennig 1966) before the type was destroyed. The enlarged abdomen in the drawing by Hull indicates that the original type was a female. The specimen examined herein is a male based on the narrower abdomen, despite the genitalia being obscured by an opaque mass. Like many Baltic Amber taxa, Eulonchiella is closely related to a group of Afrotropical genera including Dimacrocolus, Parahelle and Thyllis (Hennig 1966), all with relatively complete wing venation. Eulonchiella can be differentiated from all other Philopotinae genera by the legs not being elongate, eyes not pilose, wing venation relatively complete, proboscis elongate and palpi being present.
Diagnosis. Body shape arched; colouration non-metallic pale brown; head width slightly smaller than thorax width; shape hemispherical; postocular ridge and occiput   rounded; posterior margin of eye rounded; eyes bare; three ocelli present, medial ocellus slightly smaller; position of antennae on head nearer to mouthparts; eyes contiguous above antennal base, not contiguous below; palpi absent; proboscis much shorter than head length; flagellum shape stylate, apex with terminal seta; thorax with postpronotal lobes enlarged, medially contiguous to form collar; subscutellum not enlarged, barely visible; legs with tibial spines absent; pulvilli present; legs not greatly elongated; wing hyaline, markings absent; costa ending in radial field; costal margin straight; humeral crossvein absent; radial veins meeting wing margin before wing apex; R 1 slightly inflated distally at pterostigma; R 2+3 present, reaching wing margin; R 4+5 present as very short, single vein, not reaching wing margin; medial vein compliment with only one M vein present; discal cell absent; medial vein very short, not reaching wing margin; cell m 3 absent; crossvein 2r-m absent; Cu reduced, not reaching wing margin; anal lobe not enlarged; alula well developed; abdomen smooth, shape rounded, cylindrical, similar width to thorax.
Etymology. Derived from Latin quasi, appearing as if resembling; referring to the likeness of this species to members of Terphis.
Comments. This genus is represented by only a single species Q. fisheri sp. n. from Veracruz, Mexico. It is closely related to Terphis and Philopota based on reduction in wing veins. The position of the antennae, proximate to the reduced mouthparts, reduced wing venation and absence of abdominal tubercles readily differentiates this genus from all other philopotine genera.
Male genitalia. The genitalia were not dissected because the holotype is the only specimen available. Genitalic dissection is not necessary to diagnose the genus, since it can be differentiated based on external characters.
Etymology. This species is named in honor of Eric Fisher, the collector of the only known specimen of this unusual species.
Diagnosis. Body shape arched; colouration non-metallic dark brown; head width much smaller than thorax (female) or slightly smaller than thorax (male); head spherical; postocular ridge and occiput extended posteriorly into slight ridge; posterior margin of eye rounded; eyes bare; position of antennae on head near middle of frons, slightly nearer to mouthparts; eyes contiguous above antennal base, not contiguous below; palpi present; proboscis longer than head; antennal flagellum stylate, apex with terminal seta; thorax with postpronotal lobes enlarged, medially contiguous to form collar; subscutellum enlarged; legs not greatly elongated; tibial spines absent; pulvilli present; wing hyaline, markings absent; costa ending in radial field; costal margin straight in both sexes; humeral crossvein absent; radial veins meeting wing margin before wing apex; R 1 inflated distally at pterostigma; R 2+3 present; R 4+5 present as single vein, slightly curved anteriorly midway; veins M 1 , M 2 and M 3 present; discal cell absent; medial veins reaching wing margin (or nearly so); cell m 3 absent; crossvein 2r-m absent; Cu reduced, not reaching wing margin; anal lobe not enlarged; alula well developed; abdomen smooth, rounded, cylindrical in shape, similar width to thorax (male) or greatly rounded, inflated (female).
Etymology. This genus is named in honor of Evert I. Schlinger, not only a collector of specimens of this species, but a foremost expert on world Acroceridae taxonomy and patron of dipterology.
Comments. This genus is represented by only a single species (S. irwini sp. n.) from New Caledonia. Winterton et al. (2007) included DNA sequences for this genus in their phylogenetic analysis of the family, placing it close to the New Zealand genus Helle. Schlingeriella gen n. can be differentiated from all other philopotine genera by a combination of the following characters: inflated vein R 1 apically, medial veins mostly reaching the wing margin, absence of all wing cells except cell br, apilose eyes and elongate mouthparts. There is dramatic sexual dimorphism in body size, with females considerably larger than the diminutive males; males of this genus are some of the smallest acrocerids known.   Description. Male with small body size (male body: 2.4 mm) and wing as long as the body (male wing: 2.5 mm), female with medium body size (female body: 4.4 mm) and wing longer than the body (female wing: 6.0 mm). Head. Eyes, occiput and ocellar tubercle dark brown, occiput wider than the face; ocelli shining light brown, antennal tubercle shining black, antennae light brown, face black, clypeus shining brown, as long as the antennae, proboscis yellow. Thorax. Uniform dark brown with short whitish pile; coxae yellow, legs dark yellow, femora with darker yellow-brown suffusion, lower calypter and haltere pale yellow, wings hyaline with brown veins. Abdomen. Dark brown; female tergites I-II entirely brown, tergites III-VI with the anterior half yellow and the posterior half brown, sternites brown.
Etymology. This species is named in honour of Michael E. Irwin.

systematics of Philopotinae
While two groups can be differentiated within Philopotinae based on reduction of wing venation, three clades have been identified by Winterton et al. (2007) largely corresponding to three biogeographical regions. Philopota genus group-This genus group comprises Africaterphis from Africa, the Palaearctic Oligoneura, Archaeterphis and Prophilopota, and new world genera Philopota, Megalybus, Quasi gen n. and Terphis. Archaeterphis is a very distinctive genus, closely related to the extant genus Africaterphis (Hauser & Winterton, 2007). Prophilopota is presumably more closely related to Oligoneura, since both genera share the presence of maxillary palpi and similar shape of the antennal tubercle (Schlinger, 1971). Quasi gen n. is closely related to Philopota and in particular, Terphis. This genus shares with Terphis the insertion of the antennae on the lower side of head, reduced mouthparts, presence of relatively well-developed subscutellum and substantial reduction of the wing venation, the latter being less reduced in Philopota. In addition, both Philopota and Quasi gen n. lack the abdominal tubercles present in Terphis, and share a conical abdomen, instead of a swollen one that characterizes Terphis. Genera in the Philopota genus group are found in the northern and southern hemispheres with greater diversity in the New World (four genera). All genera in this group have reduced wing venation except Megalybus, the sister genus to the clade .
Helle genus group-Schlingeriella gen n. was included in the study by Winterton et al. (2007) as "undescribed genus New Caledonia". It is closely related to the New Zealand genus Helle, since they both have apilose eyes, well developed palpi, elongate mouthparts and an inflation of the vein R 1 at the pterostigma. Schlingeriella gen n. is differentiated from Helle by its small body size and the reduced wing venation.
Thyllis genus group-This group contains genera with complete wing venation including three Afrotropical genera (Dimacrocolus, Parahelle and Thyllis) and the Palaearctic genus Eulonchiella. Dimacrocolus and Parahelle are endemic to Madagascar while Thyllis is found in both Madagascar and South Africa.