Research Article |
Corresponding author: Justin B. Runyon ( jrunyon@montana.edu ) Academic editor: Marija Ivković
© 2022 Justin B. Runyon, Eric Beckendorf, Louis S. Hesler.
This is an open access article distributed under the terms of the CC0 Public Domain Dedication.
Citation:
Runyon JB, Beckendorf E, Hesler LS (2022) A new species of Chrysotus Meigen (Diptera, Dolichopodidae) from soybean fields in South Dakota, USA. ZooKeys 1135: 171-180. https://doi.org/10.3897/zookeys.1135.95026
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A new long-legged fly species, Chrysotus soya sp. nov. (Diptera: Dolichopodidae), is described and illustrated from specimens collected in soybean fields near Brookings, South Dakota, USA. The abundance of this species in soybeans suggests it plays an important role as a beneficial predator.
Diaphorinae, egg, natural enemy, Nearctic, new species
The genus Chrysotus Meigen (Diptera: Dolichopodidae: Diaphorinae) has a worldwide distribution with about 300 described species (
In 2016 and 2017, we collected large numbers of an undescribed species of Chrysotus on red sticky traps during a study comparing pest and beneficial insect levels between soybean pest management systems in eastern South Dakota, USA (L. Hesler and E. Beckendorf, unpublished data). However, we were unable to remove these specimens from the sticky cards in satisfactory condition for description. In 2021, we re-sampled these soybean fields using red pan traps to obtain suitable specimens, which are described herein. Two specimens of this species were also found in eastern Montana, collected in colored pan traps as part of the ongoing inventory of wild bees in Montana. The purpose of this paper is to describe this new species of Chrysotus and provide a name so that it may be used in forthcoming publications on crop management effects on natural enemies in soybeans.
This study is based on specimens collected in 2021 using red pan traps filled with a 50/50 propylene glycol/water mixture and placed in soybean fields at the USDA Agricultural Research Service (ARS), North Central Agricultural Research Laboratory (NCARL) in Brookings, South Dakota, USA. Two additional specimens were collected in 2019 and 2020 in eastern Montana using yellow, white, and blue pan traps deployed for the ongoing inventory of wild bees of Montana at Montana State University. Specimens were transferred to 70% ethanol and dry mounted on pins using hexamethyldisilixane (HMDS) (
Label data for the primary type are cited verbatim. Labels are listed from the top label down with data from each label in quotation marks and separated by a semicolon. Lines of text on labels are delimited by a slash (/) and annotations are placed in square brackets (i.e., []).
The morphological nomenclature follows
Subfamily Diaphorinae Schiner, 1864
Holotype
, ♂ labelled: “South Dakota: Brookings Co/ North Central Ag[ricultural] Res.[earch] Lab/ soybean, 44.3388°, -96.7924°/ 11 Aug 2021, red pan traps/ L. Hesler & E. Beckendorf”; “HOLOTYPE/ ♂ Chrysotus/ soya/ Runyon [red label]” (
Male and female terminalia of Chrysotus soya sp. nov., left lateral view 5 hypopygium of male 6 ovipositor of female. Abbreviations: ac – acanthophorite; epand – epandrium; ep lobe – epandrial lobe; ms – membranous swelling; pgon – postgonite; ph sheath – sheath of phallus; s – sternite; t – tergite.
Males of Chrysotus soya sp. nov. can be distinguished from other known New World species of Chrysotus by the following combination of characters: eyes contiguous below antenna; antenna entirely black (Fig.
Male (Figs
Female (Figs
The specific epithet soya is derived from soya bean, a common name of soybean, Glycine max, and should be regarded as a noun in apposition.
Montana, South Dakota.
A heavily female-biased sex ratio of approximately 10:1 (females:males) was found in specimens of Chrysotus soya sp. nov. collected in South Dakota soybean fields. This skewed sex ratio occurred in both sets of specimens used in this study, those collected in red pan traps in 2021 (57 females, 5 males), and those collected on red sticky traps in 2016–2017 (1978 females, 218 males). Whether this reflects the true sex ratio is unclear, as females could be more attracted to red color than males.
Chrysotus soya sp. nov. was abundant in soybean fields in eastern South Dakota, and in fact, was the most abundant predatory insect found in these fields (L. Hesler and E. Beckendorf, unpublished data). Because Chrysotus species are generalist predators of other arthropods, this suggests that C. soya sp. nov. could play a role in pest management. For example, aphids are a frequently reported prey of adult Dolichopodidae (
The specimens collected in Montana offer insight into the native habitat of C. soya sp. nov. Both Montana specimens were collected in prairie habitat, close to a pond or river. This species is uncommon in Montana – just two specimens were found despite intensive sampling (using yellow, blue, and white pan traps) throughout Montana from 2019–2021. This suggests that C. soya sp. nov. naturally occurs in low abundance in grassland habitat in the Northern Great Plains and is able to thrive in the conditions created in at least some soybean fields.
The occurrence of large numbers of C. soya sp. nov. in soybean fields provides an opportunity to learn more about this species, and the biology of Dolichopodidae, in general. Of particular interest is documenting what adults are feeding on, and assessing the role they might play in controlling pest species. Despite being widely abundant in agriculture, little is understood about the likely benefits Dolichopodidae provide to growers (
We thank Casey Delphia (Montana State University) for help taking photos. This research was supported in part by the USDA Forest Service, Rocky Mountain Research Station, and the USDA ARS North Central Agricultural Research Laboratory. The findings and conclusions in this publication are those of the authors and should not be construed to represent any official USDA or U.S. Government determination or policy.