Introduction
The Interior Highlands is mountainous region in the central United States. It has remained exposed for the last 270 million years and has historically acted as a refugium during times of inhospitable climate (Skvarla et al. 2015). Due to its history and geography, the region is a biodiversity hotspot that supports more than 200 endemic species (Allen 1990, Robison and Allen 1995, The Nature Conservancy, Ozarks Ecogegional Assessment Team 2003, Pringle and Witsel 2005, Zollner et al. 2005, Robison et al. 2008, Skvarla et al. 2015). However, compared to similar biodiversity hotspots, such as the Southern Appalachians, the Interior Highlands in general has been poorly surveyed. This paper, which focuses on Asilidae and certain other Diptera, is the fourth in a series that detail a survey at Steel Creek in Northwest Arkansas (see Skvarla et al. 2015 for select Coleoptera, Skvarla et al. 2016b for "Symphyta", and Skvarla et al. 2016a for Heteroptera).
Because this paper covers species from a variety of fly families, we provide the following summaries of each family and lower taxon treated.
Anisopodidae comprises 154 species world wide, including nine that are present in North America, five of which belong to Sylvicola (Pape et al. 2011, Pratt and Pratt 1980). Larval Sylvicola generally develop in decaying organic matter and may become pestiferous in sewage treatment plants (Pratt and Pratt 1980).
Asilidae, the members of which are commonly known as robber flies, are a diverse family of exclusively predatory flies. More than 7,500 species in approximately 550 genera are known worldwide, of which approximately 1,040 species in 100 genera occur in North America north of Mexico (Pape et al. 2011, Geller-Grimm 2016).
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). Five species of Rachicerus are present in the Nearctic; two are restricted to the coastal forests of the Pacific Northwest and three – R. fulvicollis Walker 1854, R. nitidus Johnson, 1903, and R. obscuripennis Loew, 1863 – are found in the eastern United States and Canada (Webb 1984).
Sampling methods
Sampling description
The sampling protocol was covered in detail by Skvarla et al. (2015). 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).
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).
Additional information
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.
Notes on newly reported species
Lasiopogon opaculus Loew, 1874 (Asilidae) (Fig. 1) is known from Ontario south through Georgia, west to Illinois, Nebraska, and Mississippi (Cannings 2002).
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).
Gowdeyana punctifera (Malloch, 1915) (Stratiomyidae) is widespread in eastern North America and occurs from Massachusetts south to Alabama, west to South Dakota, Wyoming, Utah, and Morelos and Sinaloa, Mexico (Woodley 2001).
Sargus decorus Say, 1824 (Stratiomyidae) (Fig. 5) is widespread in North America and occurs from Quebec and Ontario, south to Georgia, west to Yukon, British Columbia, Washington, and California (Woodley 2001).
Callopistromyia annulipes Macquart, 1855 (Ulidiidae) is widespread in North America and has been reported from Maine south to Louisiana, west to Washington (Kameneva and Korneyev 2005).
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. 2015, 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, Skvarla et al. 2015). 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.