Terrestrial arthropods of Steel Creek, Buffalo National River, Arkansas. IV. Asilidae and other Diptera

Abstract Background This is the fourth in a series of papers detailing the terrestrial arthropods collected during an intensive survey of a site near Steel Creek campground along the Buffalo National River in Arkansas. The survey was conducted over a period of eight and a half months in 2013 using twelve trap types, including Malaise and canopy traps, Lindgren multifunnel traps, and pan traps. New information We provide collection records for 38 species of Asilidae and other Diptera, 7 of which are new state records for Arkansas: (Asilidae) Lasiopogon opaculus Loew, 1874; (Lygistorrhinidae) Lygistorrhina sancthecatharinae Thompson, 1975; (Stratiomyidae) Cephalochrysa nigricornis (Loew, 1866), Gowdeyana punctifera (Malloch, 1915), Sargus decorus Say, 1824; (Ulidiidae) Callopistromyia annulipes Macquart, 1855; and (Xylophagidae) Rachicerus obscuripennis Loew, 1863.


Introduction
Stratiomyidae include approximately 2700 species arranged in more than 380 genera worldwide; more than 250 species in 41 genera are present in North America north of Mexico ( Woodley 2001). While some species are relatively large-bodied and commonly encountered, such as the black soldier fly, Hermetia illucens (Linnaeus, 1758), others are smaller in size and easily overlooked. Sargus, Cephalochrysa, and Gowdeyana are examples of such taxa, and are also relatively depauprate in North America, with 6, 4, and 2 species, respectively (Woodley 2001).
Lygistorrhinidae is an uncommonly collected family of Sciaroidea that is easily recognizable by the generally elongate proboscis and reduced wing venation (Thompson 1975). Of the extant taxa, Lygistorrhina (Probolaeus) Williston, 1896, which is sometimes considered a separate genus, contains nine species and is the only (sub)genus to occur in the New World, with the remaining seven genera and Lygistorrhina (Lygistorrhina) restricted to the Old World (though note that Huerta and Ibañez-Bernal 2008 reported an undescribed L. (Lygisstorrhina) from Mexico) (Papavero 1978, Vockeroth 2009, Fungus gnats online 2015. Only one species, L. santaecatharinae Thompson, 1975, is known from North America north of Mexico (Fungus gnats online 2015).
Little is known about lygistorrhinids. Most specimens are collected using passive traps (i.e., Malaise traps) or by sweep netting vegetation and almost nothing is known about their behavior and biology, including the immature stages (Vockeroth 2009).
Ulidiidae, commonly known as picture-wing flies, are distinctive for the striking wing patterning and propensity of some species to wave or flash their wings. The peacock fly, Callopistromyia annulipes, is especially noticeable as it often holds its wings above the thorax.
Rachicerus Walker, 1854, the most speciose genus of Xylophagidae, contains approximately half of the known species worldwide, and is the only genus of Xylophagidae present in tropical forests (Woodley 2011). It is also the easiest genus of Xylophagidae to identify as it is the only one in which the antennae are composed of ten or more flagellomeres and may be pectinate (Webb 1984

Sampling methods
Sampling description: The sampling protocol was covered in detail by . The following summary is provided for convenience.
The following traps were maintained within a 4 ha site at Steel Creek, Buffalo National River, Arkansas (see Geographic coverage for a description of the site): five Malaise traps, twenty-five pan traps (five of each color: blue, purple, red, yellow, white) which were randomly arranged under the Malaise traps (one of each color per Malaise trap); fifteen Lindgren multi-funnel traps (five of each color: black, green, purple); four SLAM (Sea, Land, and Air Malaise) traps with top and bottom collectors placed in the canopy; and seventeen pitfall trap sets. Additionally, ten leaf litter samples were collected for Berlese extraction when traps were serviced.
Trap placement began on 8 March 2013 and all traps were set by 13 March 2013, except Lindgren funnels, which were set on 1 April 2013. Traps set earlier than 13 March were reset on that date in order to standardize trap catch between traps. Traps were serviced approximately every two weeks. The last collection of pitfall traps and pan traps occurred on 6 November 2013; Malaise, SLAM, and Lindgren funnel traps were run for an additional month, with the final collection on 4 December 2013. In total, 1311 samples were collected.
RV and marine antifreeze, which contains both propylene glycol and ethanol, was used as the preservative in all traps as it is non-toxic, inexpensive, and preserves specimens reasonably well (Skvarla et al. 2014). Insect escape was impeded by the addition of a squirt of unscented, hypoallergenic dish detergent to the propylene glycol to act as a surfactant. Trap catch was sieved in the field and stored in Whirl-Pak bags in 90% ethanol until sorting.
Quality control: Samples were coarse-sorted using a Leica MZ16 stereomicroscope illuminated with a Leica KL1500 LCD light source and a Wild M38 stereomicroscope illuminated with an Applied Scientific Devices Corp. Eco-light 20 fiber optic light source. After sorting, specimens were stored individually or by family in 2 mL microtubes in 70% ethanol until they could be pinned or pointed.
Asilidae were identified by author Barnes, who is an internationally recognized robber fly expert. Specimens of other families were identified using published keys (Table 1).

Family Genus Reference
General identification McAlpine et al. 1981, McAlpine et al. 1987 Anisopodidae Sylvicola Asilidae were the focal group of this study; all specimens were removed when bulk samples were sorted so specimens reported here reflect the seasonality and relative abundance of the species sampled by the traps at the site. Specimens of other families were not consistentatly removed by everyone who processed samples, so specimens reported here are indicative of a species presence at the site but not other measurements such as seasonality and relative abundance.
All specimens are deposited in the University of Arkansas Arthropod Museum (UAAM).

Results
We collected and identified specimens representing 12 families, 27 genera, and 38 species during this study (Table 2). Seven species, which represent 18% of the total species identified, are recorded for the first time from Arkansas.
Lygistorrhina santaecatharinae (Lygistorrhinidae) has only been reported in the literature on two occasions and is known from localities in West Virginia, Virginia, Georgia, and Tennessee ( Fig. 2) (Thompson 1975, Vlach et al. 2010. Shortly after the specimens reported herein were collected, photographs of female L. santaecatharinae feeding on a flower, possibly Rudbeckia, from Buffalo Point recreation area (Marion County, Arkansas), a locality 70 km away from Steel Creek, were posted online (Fig. 3, via Hartley 2015). Not only do the photographs provide an additional locality in Arkansas, but they also provide the first record of nectivory in L. santaecatharinae and apparently the first record of feeding or indeed any behavior in a lygistorrhinid.  Cephalochrysa nigricornis (Loew, 1866) (Stratiomyidae) (Fig. 4) is known from Quebec and Ontario south to Georgia, west to Wisconsin, Minnesota, and Kansas (Woodley 2001    Rachicerus obscuripennis Loew, 1863 (Xylophagidae) (Fig. 6) is the only species of the genus in the eastern United States with pectinate antennae; it is found in wooded areas and has been recorded from New York south through Florida, west to Minnesota, Nebraska, Missouri, and Kansas (Fig. 7) (Webb 1984).

Discussion
It is unsurprising that only one of the twenty species of Asilidae was newly recorded in Arkansas as author Barnes has been studying robber flies in the state for over a decade. However, that such a distinctive species as Rachicerus obscuripennis has been known from Missouri since 1901 but is just now reported from neighboring Arkansas illustrates how poorly surveyedsome groups are in the state. This is in line with previous publications in this series, which also reported species previously unrecorded in Arkansas, some of which are quite distinctive , Skvarla et al. 2016b, Skvarla et al. 2016a).
Previous publications have utilized social media and citizen science websites such as Facebook, Flickr, and Bugguide to discover new species (e.g., Winterton et al. 2012, Otto et al. 2014, Gonella et al. 2015 and expand the known range of described species (e.g., Pérez-Hidalgo et al. 2011. The photographs that depict nectivory in Lygistorrhina sanctaecatharinae highlight the potential importance of such websites in of the study of natural history and illustrate how they can connect researchers with photographs of behavior in species that are rarely seen alive.