Morphological Description and Potential Geographic Distribution of the Genus Dolichopus Latreille (Diptera, Dolichopodidae, Dolichopodinae) in Inner Mongolia, China

Simple Summary The genus Dolichopus is a natural enemy of insects. Some of the species are widely distributed, and have the potential to develop into natural insect enemies. Through investigations of the local genus Dolichopus in Inner Mongolia, more than 1600 adult long-legged flies were collected, with many of the samples belonging to the subfamily Dolichodinae. Three new Dolichopus species were discovered, and another twelve known species were recorded, including the newly discovered subgenus Hygroceleuthus, which tremendously enriched the diversity of Dolichopus in Inner Mongolia. To have a better understanding of insect diversity and the efficiency of specimen collection in Inner Mongolia, we determined the potential geographic distribution of the genus using a Maximum Entropy (MaxEnt) model. Abstract Eight species of Dolichopus Latreille were previously recorded in Inner Mongolia. However, there have been only a few studies on their potential distribution. Here, three newly discovered species from Inner Mongolia are described, namely Dolichopus (Dolichopus) apicimaculatus sp. nov., Dolichopus (Dolichopus) jiufengensis sp. nov., and Dolichopus (Dolichopus) luae sp. nov. There were also twelve known Dolichopus species that were newly recorded in Inner Mongolia, including the newly recorded subgenus Hygroceleuthus. A key to the Dolichopus species from Inner Mongolia and the potential geographic distribution of Dolichopus in Inner Mongolia were provided. Potential geographic distribution of the genus in Inner Mongolia were determined as well.


Introduction
Inner Mongolia is part of the Mongolian Plateau, which was created by Qinghai-Tibet Plateau uplift [1,2].The climate is strongly influenced by plateau uplift, which resulted in Inner Mongolia having a temperate continental climate with relatively high precipitation but low temperatures in the northeast and low precipitation but high temperatures in the southwest [3].This contrast, in combination with Himalayan orogeny and Quaternary glaciation, significantly influenced the distribution pattern of the plants and animals in Inner Mongolia, which have evolved into groups that are highly adapted to their environment and geographical location.
Dolichopus Latreille is one of the largest genera in the subfamily Dolichopodidae with 644 species, of which more than 300 species have been recorded in the Palaearctic region and 72 species are distributed in China [4][5][6].Previously, eight species have been recorded in Inner Mongolia.However, Inner Mongolia is in the Palaearctic realm, where most of the genus Dolichopus is distributed [5].Therefore, it was predicted that the genus Insects 2023, 14, 935 2 of 22 Dolichopus likely has more than eight species in Inner Mongolia.In addition, global warming, overgrazing, and human activities have influenced the Dolichopus populations and distribution in Inner Mongolia over the years.Thus, global warming is likely to affect the distribution of Dolichopus species in the future.Most Dolichopus species are predators [5,[7][8][9][10][11], and they prefer wet conditions like streams and lakes [5,12].
Currently, research on Dolichopus has mainly focused on their morphology and phylogeny, and there have been only a few studies on the potential distribution of Dolichopus in Inner Mongolia.Therefore, to further understand the diversity and distribution of Dolichopus in Inner Mongolia, a study was conducted on their potential geographic distribution.The regions that were suitable for the genus were also identified.Three new species of Dolichopus from Inner Mongolia were described, namely Dolichopus (Dolichopus) Loew, 1848.Previously, the low number of recorded species in Inner Mongolia was probably the result of a low number of investigations [5].The subgenus Hygroceleuthus was also newly recorded in Inner Mongolia.A key to Dolichopus from Inner Mongolia was also provided.These findings will benefit the further study of Dolichopus in Inner Mongolia.

Specimen Collection and Morphology
In this study, the specimens on which this study is based were collected in Inner Mongolia using a sweeping net and stored at the Entomological Museum of China Agricultural University, Beijing, China.The label data of the materials are described below.
The genitalic preparations of the males were made by macerating the apical portion of the abdomen in cold 10% NaOH for 12-15 h.The observations and illustrations were made using a ZEISS Stemi 2000-C (ZEISS, Oberkochen, Germany) stereomicroscope.Photographs were taken with a Canon EOS 77D (Canon, Tokyo, Japan) digital camera through a macro lens.All images were optimized and grouped into plates using Adobe Photoshop CC 2017.
The specimens that were preserved in the Biological Collections of China Agricultural University  were examined and the Dolichopus species that were recorded in this study were found to be distributed in different places in Inner Mongolia (Figure 1).

Potential Distribution
The occurrence data of Dolichopus were collected during field investigations around Inner Mongolia (Figure 1).Records that did not have an accurate latitude and longitude were excluded.A Maximum Entropy (MaxEnt) model was used to find the probability distribution of the maximum entropy of the known distribution data and related occurrence localities, which can be used to evaluate and model the distribution patterns of species [14].The MaxEnt model was found to be more accurate than other distribution models when only occurrence data was available [15].The MaxEnt model was used to predict the potential distribution of Dolichopus insects according to the collection records and occurrence records of Dolichopus in Inner Mongolia, which provided a potential distribution for Dolichopus in Inner Mongolia and more information for species collection.The MaxEnt model was constructed using the occurrence records in Figure 1, and it was based on climate, vegetation type, soil type, and elevation variables.
The climatic variables that were used for modeling were obtained from the World-Clim Database (http://www.worldclim.org/,accessed on 20 March 2023).Nineteen climate variables that were recorded between 1950 and 2000 were used (Bio1-19).Digital elevation models were downloaded from Geospatial Data Cloud (https://www.gscloud.cn,accessed on 19 March 2023, Chinese Academy of Sciences).Image resolution was set at 2.5 arc min (about 5 km at the equator).Data on the vegetation and soil types were obtained from a national database, which was updated in 2008 and 2015 and had a resolution of 2.5 arc min (about 5 km at the equator).River data were obtained from the digital elevation model.The data are shown in Figure 2.

Potential Distribution
The occurrence data of Dolichopus were collected during field investigations around Inner Mongolia (Figure 1).Records that did not have an accurate latitude and longitude were excluded.A Maximum Entropy (MaxEnt) model was used to find the probability distribution of the maximum entropy of the known distribution data and related occurrence localities, which can be used to evaluate and model the distribution patterns of species [14].The MaxEnt model was found to be more accurate than other distribution models when only occurrence data was available [15].The MaxEnt model was used to predict the potential distribution of Dolichopus insects according to the collection records and occurrence records of Dolichopus in Inner Mongolia, which provided a potential distribution for Dolichopus in Inner Mongolia and more information for species collection.The MaxEnt model was constructed using the occurrence records in Figure 1, and it was based on climate, vegetation type, soil type, and elevation variables.
The climatic variables that were used for modeling were obtained from the WorldClim Database (http://www.worldclim.org/,accessed on 20 March 2023).Nineteen climate variables that were recorded between 1950 and 2000 were used (Bio1-19).Digital elevation models were downloaded from Geospatial Data Cloud (https://www.gscloud.cn,accessed on 19 March 2023, Chinese Academy of Sciences).Image resolution was set at 2.5 arc min (about 5 km at the equator).Data on the vegetation and soil types were obtained from a national database, which was updated in 2008 and 2015 and had a resolution of 2.5 arc min (about 5 km at the equator).River data were obtained from the digital elevation model.The data are shown in Figure 2.
Next, MaxEnt (https://biodiversityinformatics.amnh.org/open_source/maxent/,accessed on 7 July 2022) was used to clarify the potential distribution of Dolichopus.The model was cross-validated using a 25% subset of randomly selected data points for testing, and 75% of the points were reserved for training.The jackknife method modeled the contribution of the eco-environmental variables to the distribution of the genus Dolichopus.
Variables with a correlation coefficient (r) > 0.7 were considered to make a significant contribution to the model.A receiver operating characteristic (ROC) curve analysis was used to evaluate the performance of the model in predicting the distribution of the genus Dolichopus in China.The model accuracy (area under the curve) was 0.50 with graphical environmental variable averages of 0.80-0.90(good) and 0.90-1 (excellent).

Description of New Species
Members of Dolichopus can be identified by the following features: hind tarsomere 1 with strong dorsal bristles; wing with costal callus indistinct to long and thick, M weakly bent without rudimentary M 2 or strongly bent at a right angle with rudimentary M 2 ; male Insects 2023, 14, 935 5 of 22 genitalia with cercus usually rather large and nearly quadrate with distinct finger-like marginal denticles and bristles [5,16]

Diagnosis.
Postpedicel short and blunt, with narrow baso-ventral area yellow; arista nearly apical.Wing slightly long and narrow, distinctly dark brown at tip; costal callus indistinct; M weakly bent.Calypter with black hairs.Hypandrium tubular at tip.
Description.Male (Figure 2B).Body length 3.7-3.8mm, wing length 3.4-3.6mm.Head metallic green with pale grey pollinosity.Face yellow, almost as wide as postpedicel.Hairs and bristles on head black, but middle and lower postocular bristles yellow.Antenna (Figure 4A) with scape and pedicel yellow; postpedicel black except narrow baso-ventral area yellow, relatively small, almost as long as wide, blunt at tip; arista black with short hairs, basal segment 0.3 times as long as apical segment.Proboscis brown with black hairs; palpus yellow with black hairs and 1 black apical bristle.
Thorax metallic green with pale grey pollinosity.Hairs and bristles on thorax black; 5-6 irregularly biseriate acr short hair-like, 6 long strong dc.Scutellum with 2 pairs of sc and several short yellow marginal hairs, basal pair hair-like.Propleuron with short yellowish hairs and 1 black bristle on lower portion.
Legs entirely yellow.Fore coxa yellow; mid and hind coxae black, but yellow at tip; tarsi dark brown from tip of tarsomere 1 onwards.Hairs and bristles on legs black.Mid and hind coxae each with 1 outer bristle; mid and hind femora each with 1 preapical bristle.Fore tibia with 2-3 ad, 2 pd, 1 postero-ventral bristle, 2 black black apical bristles and 1 brown apico-ventral bristle (1/2 as long as fore tarsomere 1); mid tibia with 2-3 ad, 1 pd, 1 av and 4 apical bristles; hind tibia with 4 ad, 4 pd, 1 apico-dorsal bristle, 1 av and 2 apical bristles.Hind tarsomere 1 with 1 long ad and 1 long pd.Relative lengths of tibia and 5 tarsomeres of legs LI: 2.  Head metallic green with pale grey pollinosity.Face yellow, almost as wide as postpedicel.Hairs and bristles on head black, but middle and lower postocular bristles yellow.Antenna (Figure 4A) with scape and pedicel yellow; postpedicel black except narrow basoventral area yellow, relatively small, almost as long as wide, blunt at tip; arista black with short hairs, basal segment 0.3 times as long as apical segment.Proboscis brown with black hairs; palpus yellow with black hairs and 1 black apical bristle.
Thorax metallic green with pale grey pollinosity.Hairs and bristles on thorax black; 5-6 irregularly biseriate acr short hair-like, 6 long strong dc.Scutellum with 2 pairs of sc and several short yellow marginal hairs, basal pair hair-like.Propleuron with short yellowish hairs and 1 black bristle on lower portion.
Abdomen metallic green with pale grey pollinosity.Hairs and bristles on abdomen black.Male genitalia (Figure 4D): Epandrium distinctly longer than wide; inner epandrial lobe relatively short and thick, bent forwards, outer epandrial lobe large and wide with 2 curved apical bristles.Postgonite (Figure 4C) almost as long as dorsal lobe of surstylus.Male cercus nearly square with distinct finger-like marginal processes bearing apical bristles.Hypandrium somewhat tubular at tip.
Remarks.This new species is somewhat similar to Dolichopus zernyi Parent, 1927, but can be distinguished by the postpedicel blunt at tip, 6 dc and the inner epandrial lobe narrow and curved at tip.In D. zernyi, the postpedicel is acute at tip, 5 dc are present, and the inner epandrial lobe is wide and not curved at tip [5].This new species is somewhat similar to Dolichopus asiaticus Negrobov, 1973 but can be distinguished by the postpedicel blunt at tip and the male cercus with 4 distinct finger-like marginal processes and the ventral lobe of surstylus relatively thin and long and the phallus relatively long.In D. asiaticus, the postpedicel is pointed at tip and the male cercus is with indistinct finger-like marginal processes and the ventral lobe of surstylus is relatively short and strong and the phallus is very short [18,19].
Etymology.This species is named after the dark brown pattern on anterior part of wing.Diagnosis.Postpedicel entirely black.Costal callus long and thick; M bent in a right angle, with rudimentary M2.Fore tibia with long ventral bristles apically (half as long as fore tarsomere 1); hind tarsomere 1 with 2 dorsal bristles.Hypandrium obtuse apically; outer epandrial lobe long and thin.
Description.Male (Figure 2I).Body length 4.0-4.5 mm, wing length 4.5-4.9mm.Head metallic green with pale grey pollinosity.Face with silvery pollinosity, almost as wide as postpedicel.Hairs and bristles on head black, but middle and lower postocular bristles and posteroventral hairs yellow.Antenna (Figure 5A) blackish, but scape dark brownish yellow at basal half of ventral surface; postpedicel black, 1.4 times longer than wide, blunt at tip; arista black with short hairs, basal segment 0.35 times as long as apical segment.Proboscis brownish yellow with brown hairs; palpus yellow with blackish hairs and 1 black apical bristle.
Thorax metallic green with pale grey pollinosity.Hairs and bristles on thorax black; 7-8 irregularly biseriate acr short hair-like, 6 long strong dc.Scutellum with 2 pairs of sc Diagnosis.Postpedicel entirely black.Costal callus long and thick; M bent in a right angle, with rudimentary M 2 .Fore tibia with long ventral bristles apically (half as long as fore tarsomere 1); hind tarsomere 1 with 2 dorsal bristles.Hypandrium obtuse apically; outer epandrial lobe long and thin.
Description.Male (Figure 2I).Body length 4.0-4.5 mm, wing length 4.5-4.9mm.Head metallic green with pale grey pollinosity.Face with silvery pollinosity, almost as wide as postpedicel.Hairs and bristles on head black, but middle and lower postocular bristles and posteroventral hairs yellow.Antenna (Figure 5A) blackish, but scape dark brownish yellow at basal half of ventral surface; postpedicel black, 1.4 times longer than wide, blunt at tip; arista black with short hairs, basal segment 0.35 times as long as apical segment.Proboscis brownish yellow with brown hairs; palpus yellow with blackish hairs and 1 black apical bristle.
Thorax metallic green with pale grey pollinosity.Hairs and bristles on thorax black; 7-8 irregularly biseriate acr short hair-like, 6 long strong dc.Scutellum with 2 pairs of sc and several short marginal yellow hairs, basal pair hair-like.Propleuron with short yellow hairs and 1 black bristle on lower portion.
Legs mostly yellow.Fore coxa yellow; mid coxa black, yellow at tip; hind coxa yellow, tinged with blackish speckle at base.Fore and mid tarsi brownish to brown from tip of tarsomere 1 onwards; tip of tibia and tarsus black.Hairs and bristles on legs black.Mid and hind coxae each with 1 outer bristle; mid and hind femora each with 1 preapical bristle.
Abdomen metallic green with pale grey pollinosity.Hairs and bristles on abdomen black.Sternites 2-3 with dark yellow hairs.Male genitalia (Figure 5B): Epandrium distinctly longer than wide; inner epandrial lobe relatively short and narrow but long and thin on the opposite, finger-like, outer epandrial lobe wide and large with 1 winding apical bristle.Postgonite (Figure 5E) shorter than dorsal lobe of surstylus.Male cercus nearly square with distinct finger-like marginal processes bearing apical bristles.Hypandrium (Figure 5C Remarks.This new species is somewhat similar to Dolichopus cuneipennis Parent, 1926, but can be distinguished from the latter by the postpedicel 1.4 times longer than wide and entirely black and hind tibia black at tip.In D. cuneipennis, the postpedicel is 1.1 times longer than wide, its baso-ventral area is brownish yellow, and the apical 2/3 of the hind tibia is black [5].This new species is somewhat similar to Dolichopus stackelbergi Smirnov, 1948 but can be distinguished by the face as wide as postpedicel and the hind tibia normal and the male cercus nearly square and the squama with black hairs.In D. stackelbergi, the face is twice as wide as postpedicel and the hind tibia is somewhat thickened and the male cercus is narrow at base, nearly trapezoidal and the squama is with dominance of black hairs and some yellow hairs [18,28]. Etymology.The species is named after the collecting area, Mount Jiufeng.Diagnosis.Antenna blackish but scape and pedicel dark yellow ventrally, postpedicel ventrally dark yellow at base; postpedicel moderately elongated, 2 times longer than wide, blunt at tip.Costal callus long and thick; M weakly bent without rudimentary M2.Fore tibia with relatively long ventral bristles apically (half as long as fore tarsomere 1); hind tarsomesre 1 with 1 dorsal bristle.
Description.Male (Figure 2K).Body length 3.8-3.9mm, wing length 3.4-3.5 mm.Head metallic green with pale grey pollinosity.Face with silvery pollinosity, almost as wide as postpedicel.Hairs and bristles on head black, but middle and lower postocular bristles and posteroventral hairs yellow.Antenna (Figure 6A) blackish but scape, pedicel dark yellow ventrally, postpedicel ventrally dark yellow at base; postpedicel moderately elongated, 2 times longer than wide, blunt at tip; arista blackish with short hairs, basal segment 0.85 times as long as apical segment.Proboscis brownish yellow with brown hairs; palpus yellow with brown hairs and 1 brown apical bristle.Diagnosis.Antenna blackish but scape and pedicel dark yellow ventrally, postpedicel ventrally dark yellow at base; postpedicel moderately elongated, 2 times longer than wide, blunt at tip.Costal callus long and thick; M weakly bent without rudimentary M 2 .Fore tibia with relatively long ventral bristles apically (half as long as fore tarsomere 1); hind tarsomesre 1 with 1 dorsal bristle.
Description.Male (Figure 2K).Body length 3.8-3.9mm, wing length 3.4-3.5 mm.Head metallic green with pale grey pollinosity.Face with silvery pollinosity, almost as wide as postpedicel.Hairs and bristles on head black, but middle and lower postocular bristles and posteroventral hairs yellow.Antenna (Figure 6A) blackish but scape, pedicel dark yellow ventrally, postpedicel ventrally dark yellow at base; postpedicel moderately elongated, 2 times longer than wide, blunt at tip; arista blackish with short hairs, basal segment 0.85 times as long as apical segment.Proboscis brownish yellow with brown hairs; palpus yellow with brown hairs and 1 brown apical bristle.
Thorax metallic green with pale grey pollinosity.Hairs and bristles on thorax black; 6-7 irregularly biseriate acr short hair-like, 6 long strong dc.Scutellum with 2 pairs of sc and several short marginal yellow hairs, basal pair hair-like.Propleuron with short yellow hairs and 1 black bristle on lower portion.
Abdomen metallic green with pale grey pollinosity.Hairs and bristles on abdomen black.Male genitalia (Figure 6D): Epandrium distinctly longer than wide; inner epandrial lobe relatively small, outer epandrial lobe wide and large with 2 apical bristles (one strong and straight, one thin and bent), sunken areas between two lobes relatively small.Postgonite (Figure 6C) shorter than dorsal lobe of surstylus.Male cercus (Figure 6B) nearly square with distinct finger-like marginal processes bearing apical bristles.Hypandrium somewhat thick at tip.
Remarks.This new species is somewhat similar to Dolichopus longicornis Stannius, 1831, but can be distinguished from the latter by the following features: antenna moderately elongated, postpedicel 2 times longer than wide and blunt at tip; scape and pedicel dark yellow ventrally; postpedicel ventrally dark yellow at base; hind tarsomere 1 with 1 dorsal bristle.In D. longicornis, the antenna is distinctly elongated, the postpedicel is 2.6 times longer than wide and blunt at tip, the antenna is entirely black and the hind tarsomere 1 is with 2 dorsal bristles [5].This new species is somewhat similar to Dolichopus albipalpus Negrobov, 1973 but can be distinguished from the face as wide as postpedicel and the fore tibia with no antero-dorsal bristle in apical part and the outer epandrial lobe with 1 short bristle at base and 1 long bristle between outer epandrial lobe and inner epandrial lobe and the ventral lobe of surstylus with 1 bristle and the dorsal lobe of surstylus with no bristle.In D. albipalpus, the face is narrower than the postpedicel and the fore tibia is with a row of short antero-dorsal bristles in apical part and the outer epandrial lobe is with 1 relatively long bristle at base and 1 relatively short bristle between outer epandrial lobe and inner epandrial lobe and the ventral lobe of surstylus is with more than 1 bristle and the dorsal lobe of surstylus is with several spine-like bristles [18,19].
Etymology.The species is named after the collector Xiumei Lu.
3.1.12.Dolichopus longicornis Stannius, 1831 Figures 3D and 7A   in the Hailar River Basin, Argun River Basin, Nen River Basin, and Hulun Lake of northeastern Inner Mongolia; the upper and middle reaches of the Taoer River Basin, lower reaches of the Huolin River, Xiliao River Basin, Xar Moron River Basin, middle and southern part of the Da Hinggan Mountains of eastern Inner Mongolia; the Otindag Sandy Land, Daqing Mountain Range, eastern part of the Yellow River Basin in middle Inner Mongolia; and the Helan Mountain Ranges and Yabulai Mountain of western Inner Mongolia (Figure 8).

Discussion
So far, three subgenera, Dolichopus, Hygroceleuthus and Macrodolichopus are known to occur in China, and two of them are known to occur in Inner Mongolia.Brooks considered Hygroceleuthus and Macrodolichopus of no taxonomic value due to the variable characters of the antenna and clypeus [42].However, Negrobov considered Hygroceleuthus distinct based on the antennae and wings of both the males and females [43].Hygroceleuthus is considered by some scholars to be a subgenus while others considered it to be an independent genus or synonym [16,23,37,[44][45][46][47][48].It includes 13 species worldwide and 4 species in China [5,42,49]

Discussion
So far, three subgenera, Dolichopus, Hygroceleuthus and Macrodolichopus are known to occur in China, and two of them are known to occur in Inner Mongolia.Brooks considered Hygroceleuthus and Macrodolichopus of no taxonomic value due to the variable characters of the antenna and clypeus [42].However, Negrobov considered Hygroceleuthus distinct based on the antennae and wings of both the males and females [43].Hygroceleuthus is considered by some scholars to be a subgenus while others considered it to be an independent genus or synonym [16,23,37,[44][45][46][47][48] The Dolichopus species were widely distributed in Inner Mongolia.Every city had records of Dolichopus species except for Bayan Nur.At the same time, it seems that Dolichopus is adapted to three ecosystems in Inner Mongolia.For instance, it was found that Dolichopus were distributed in the mountains of the nature reserves in Inner Mongolia (Mount Jiufeng, Mount Helan, Saihanwula, Arxan, and Daqinggou) and the grasslands in Hulun Buir, Tongliao, Sonid Left Banner, Abaga, West Ujimqin Banner, and East Ujimqin Banner.Moreover, the wetlands in Hinggan League and Hulun Buir also recorded occurrences of Dolichopus species.However, the species level distribution patterns were quite different.Some species were distributed widely while some species only occurred in one place.The larvae of Dolichopus are aquatic and semi-aquatic while the adults appear in wet conditions, such as rivers, lakes, and forests [5,12].The results of the MaxEnt model illustrated that the moderately, extremely, and highly suitable areas for Dolichopus were mainly distributed near water, such as in river basins (Figure 8).The largest extremely and highly suitable area was in Hulun Buir, which could be due to the vegetation or the river basins.The results also showed that the Helan and Yabulai Mountain Ranges (Alxa League) were extremely and highly suitable for the occurrence of Dolichopus.The Helan Mountains are steep on their east side, which obstructs the southeast monsoon when it moves westwards.The air current climbs upwards, resulting orographic rain [50,51] and a large area with a semi-humid climate in the Helan Mountains.This could provide suitable climatic conditions for Dolichopus.Additionally, the Yabulai Mountains are located in temperate desert arid regions with no permanent rivers.However, due to the cover that is provided by the landform in the south valley, there is floating water in the Yabulai Mountains, which could be the reason for the occurrence of Dolichopus.Moreover, there were some extremely, highly, and moderately suitable areas in the Otingdag Sandy Land (Xilin Gol League), and there is a gradient of precipitation in the Otingdag Sandy Land which is relatively high in the east and relatively low in the west [52].Furthermore, the Otingdag Sandy Land is a famous desert with many water holes and streams which could explain the occurrence of Dolichopus.
Generally, the potential geographic distribution (Figure 8) corresponded with the distribution pattern (Figure 1).However, with continuing investigations, insect distribution and diversity will become clearer.This study will provide basic data if Dolichopus species become the main predator with the changing of the weather.

Conclusions
This taxonomic study improved the knowledge of Dolichopus in Inner Mongolia.In this study, three new species and twelve newly recorded species were found in Inner Mongolia, which increased the number of Dolichopus species recorded in Inner Mongolia from eight to twenty-three.The number of the species of the genus in Inner Mongolia should increase as investigations continue.This study also indicated the potential distribution of Dolichopus in Inner Mongolia.Generally, the potential geographic distribution corresponded with the distribution records.Further research should focus on collecting more specimens near river basins, especially in Hulun Buir, as well as the sandy land in Xilin Gol League.Thus, the diversity of Dolichopus in Inner Mongolia was elucidated, and the potential distribution of the genus was provided.At the same time, the taxonomic study and potential geographic distribution provided basic data for further study.

Figure 8 .
Figure 8. Potential geographic distribution of Dolichopus in Inner Mongolia.
. D.(H).Brevifacies Stackelberg, 1925 and Tibet.D.(H).rotundipennis Loew, 1848 were distributed in Qinghai.D.(H).latipennis Fallén, 1832 and D.(H).tenuicornis Parent, 1927 had no records of their distribution in Chinese provinces.D.(H).rotundipennis Loew, 1848 was newly recorded in Inner Mongolia and distributed in Hulun Buir and West Ujimqin Banner.The subgenus Macrodolichopus had two species distributed in China, namely D.(M).diadema Haliday, 1832 and D.(M).obscuripes Stackelberg, 1925, both of which are distributed in Qinghai province.The subgenus Dolichopus has many more species than the other two subgenera and they are distributed widely in China.When combined with the records from this study, the provinces in southern China had fewer records of the genus Dolichopus than those in northern China, where Inner Mongolia is

Figure 8 .
Figure 8. Potential geographic distribution of Dolichopus in Inner Mongolia.
. It includes 13 species worldwide and 4 species in China [5,42,49].D.(H).Brevifacies Stackelberg, 1925 and Tibet.D.(H).rotundipennis Loew, 1848 were distributed in Qinghai.D.(H).latipennis Fallén, 1832 and D.(H).tenuicornis Parent, 1927 had no records of their distribution in Chinese provinces.D.(H).rotundipennis Loew, 1848 was newly recorded in Inner Mongolia and distributed in Hulun Buir and West Ujimqin Banner.The subgenus Macrodolichopus had two species distributed in China, namely D.(M).diadema Haliday, 1832 and D.(M).obscuripes Stackelberg, 1925, both of which are distributed in Qinghai province.The subgenus Dolichopus has many more species than the other two subgenera and they are distributed widely in China.When combined with the records from this study, the provinces in southern China had fewer records of the genus Dolichopus than those in northern China, where Inner Mongolia is located.With more studies, the distribution pattern of Dolichopus in China can be better clarified.

Author Contributions:
Conceptualization, D.Y. and N.W.; resources, D.Y. and N.W.; writingoriginal draft preparation, X.Q. and X.D.; visualization X.Q. and X.D.; writing-review and editing, N.W. and D.Y.; project administration, N.W.All authors have read and agreed to the published version of the manuscript.Funding: This work was funded by National Natural Science Foundation of China (32370503), Natural Science Foundation of Inner Mongolia (2020JQ04), National Science & Technology Fundamental Resources Investigation Program of China (Grant No. 2019FY100400) and Key Science and Technologies Program of Inner Mongolia (No. 2021ZD0011-2).Institutional Review Board Statement: Not applicable.Data Availability Statement:Data supporting results in this study can be obtained through contact with the first author (X.Y.).