A New Species of Brachynemurus Hagen in the B. versutus Subgroup (Neuroptera, Myrmeleontidae, Brachynemurini) from the Sonoran Province, Mexico ^†

Abstract

Brachynemurus bowlesi, sp. n. is a newly discovered myrmeleontid from the Sonoran Province, the northernmost subtropical region of Mexico. The new species fits within the Brachynemurus versutus subgroup, which now includes five species, all of them occurring in Mexico and the central and western United States. The new species may be identified by characteristics of the internal male genitalia, especially by a roof-like mediuncus, as well as the basal part of the 10th gonostyli, with paired processes in an acute angle and a shield-like expansion more evident in the dorsocaudal view. The formerly proposed synonymy of Brachynemurus mexicanus Banks, under B. versutus (Walker), is herein reinstated and supported.

1. Introduction

Myrmeleontidae (including antlions) is the most diverse family within the order Neuroptera, with approximately 299 genera and 2138 known species [1,2], most of them recorded from arid or semi-arid environments [3]. Antlions are recognized by their clubbed antennae of variable length, as well as long and slender wings, with a hypostigmatic cell near the pterostigma of both wings in most species, and a long abdomen [3]. Both larvae and adults are predators; larvae may actively forage, generally on soil or vegetation, or live in a sedentary state, waiting for prey, while adults are flying hunters [2,3]. Taxonomy at the genus level is relatively well-known; however, there are still many genera in need of revision [4,5,6].

The genus Brachynemurus Hagen was originally proposed with B. longicaudus as a type species, previously assigned to the genus Myrmecoleon [6,7,8]. Brachynemurus was later revised in a monograph of the North American tribe Brachynemurini [6] and subsequently, in a reclassification of the tribe, where some species were placed in new genera [9,10]. A recent phylogenomic study recovered the genus as monophyletic [1], yet partial taxonomic sampling still warrants further corroboration of its monophyly. Previously, one morphological autapomorphy had been proposed for the genus, an apically narrow ectoproct in males; however, this trait only applies to 8 of the 22 currently valid species [10].

Brachynemurus is distributed both in the Nearctic and Neotropics, with the majority of species found in North America (

Table 1. Species groups and distribution of Brachynemurus Hagen (after Stange [6,7,10] and Oswald [11]).

Species Group	Species Subgroup	Species	Distribution
B. nebulosus	B. abdominalis	Brachynemurus abdominalis (Say)	Canada, Mexico, United States
		Brachynemurus blandus (Hagen)	United States
		Brachynemurus irregularis Currie	United States
		Brachynemurus signatus (Hagen)	United States
	B. versutus	Brachynemurs bowlesi, n. sp.	Mexico
		Brachynemurus divisus (Navás)	Mexico
		Brachynemurus elongatus Banks	Mexico, United States
		Brachynemurus hubbardii Currie	Mexico, United States
		Brachynemurus versutus (Walker)	Mexico, United States
	B. nebulosus	Brachynemurus carolinus Banks	United States
		Brachynemurus ferox (Walker)	Canada, Mexico, United States
		Brachynemurus henshawi (Hagen)	United States
		Brachynemurus longicaudus (Burmeister)	United States
		Brachynemurus nebulosus (Olivier)	Canada, United States
		Brachynemurus ramburi Banks	United States
		Brachynemurus seminolae Stange	United States
B. fuscus	–	Brachynemurus californicus Banks	Mexico, United States
		Brachynemurus fuscus (Banks)	Mexico, United States
B. pulchellus	–	Brachynemurus exiguus (Navás)	Mexico
		Brachynemurus pulchellus Banks	Mexico, United States
B. sackeni	–	Brachynemurus sackeni Hagen	Mexico, United States
		Brachynemurus eiseni Hagen	Mexico, United States

) [5,6,10]. Four species groups, one of them with three subgroups, are recognized (Table 1) [5,10]. This classificatory scheme was based on diagnostic (adult, nongenital morphology) [6], rather than phylogenetic characteristics. In particular, the Brachynemurus nebulosus group is divided into the B. abdominalis, B. versutus, and B. nebulosus subgroups. Characteristics to distinguish the Brachynemurus versutus subgroup include the absence of bristles on the forefemur, the lack of pilula axillaris, and a simple (with uniform width) postventral lobe of the male ectoproct [6]. These subgroups did not emerge as monophyletic in Machado et al.’s phylogenomic analysis [1], which suggests that this classification requires revision.

Thirty years after the last Brachynemurus revision [10], a new species is herein described, derived from survey work in Mexico’s state of Sonora, a region holding considerable richness in regards to this group [5,6,10]. Moreover, we revalidate a formerly proposed synonymy of B. mexicanus Banks under B. versutus Walker [12], which leaves Brachynemurus with a total of 22 valid species.

2. Materials and Methods

2.1. Specimens and Study Sites

A total of 24 male specimens of the new species were collected during an expedition to the southern part of the state of Sonora in September 2019. A series of female specimens were also collected; however, it was not possible to associate them with identified males, largely because of a strong external resemblance between Brachynemurus hubbardii and the new species. Six more male specimens already deposited in the Colección Nacional de Insectos (CNIN) of Instituto de Biología, Mexico’s National University (UNAM), were added to the paratypes series.

2.2. Dissection, Curation, and Identification

Specimens were captured on a light trap, with mercury vapor and UV lamps against a white sheet. Insects were preserved in 80% ethyl alcohol and later pinned and dissected in the laboratory. To study the genitalia morphology, the last three abdominal segments were removed and cleared for 15 min in 10% potassium hydroxide (KOH), then rinsed with distilled water; in most males, the 9th gonostyli and gonarcus (10th gonocoxite–10th gonostylus complex) were separated (extracted) from the rest of the terminalia. Finally, genitalic structures were stored in a microvial with glycerin, which were pinned with the respective specimen. Selected gonarcus were separated and stained with Chlorazol black E diluted in ethanol. Specimens were identified with original species descriptions, as well as with keys obtained from Stange [6,7,10], and through comparison with type specimens. The wing terminology developed by Breitkreuz et al. [13], with modifications, is used. The general morphology of Stange [6] served as a reference. Regarding male genitalia terminology, we adhere to that of Marquez-López et al. [2], where an appendicular origin [14] is assumed for the gonarcus (fused 10th gonocoxites + 10th gonostyli), in agreement with a Neuropterida groundplan, yet with a distal portion (gonostylus) of gonarcus separated from the basal part (gonocoxite). Habitus photographs were captured with a Canon EOS REBEL T7 camera and a 24–105 mm lens, mounted on a copy stand. General morphology and genitalia observations were conducted under a Carl Zeiss Discovery V8 stereomicroscope, and images of terminal abdominal structures were captured with a Carl Zeiss AxioZoom V16 stereomicroscope with an automontage system. The wing diagrams were created using Adobe Illustrator software using original photographs.

The holotype and 23 paratypes were deposited in the Colección Nacional de Insectos (CNIN), Instituto de Biología, UNAM, with additional male paratypes deposited as follows: two in the California Academy of Sciences (CAS), San Francisco; two in the Museum of Comparative Zoology (MCZ), Harvard University, Cambridge, Massachusetts; two in the National Museum Natural History, Smithsonian Institution (NMNH), Washington, D. C.; two in the Department of Entomology, Texas A&M University, College Station (TAMU); and two in the Florida State Collection of Arthropods (FSCA), Gainesville. Unless specified, all specimens are located in CNIN.

2.3. Distribution

New state records of species are marked in bold. The distribution map was created using QGIS software version 3.36.1, with regionalization of ecoregions metadata for the Mexico, Neotropical, and Nearctic regions [15,16,17,18,19]. Hypsometry metadata were downloaded from the Portal de Geoinformación of the Sistema Nacional de Información sobre Biodiversidad (CONABIO, Mexico) to create an elevation map. Original records from specimens sampled in September 2019 in Sonora, as well as records from specimens previously deposited at CNIN that belong to species of the Brachynemurus versutus subgroup, were mapped. For specimens that were not georeferenced, a midpoint on the municipality was captured to obtain the coordinates in a decimal format for the purpose of depicting the presence of the species. Records from the bibliography and from the GBIF database were also mapped. Previously published records lacking a georeference were also mapped at the midpoint of the corresponding municipality. The Spanish abbreviation “msnm” from label data of examined specimens corresponds to “meters above sea level, m.a.s.l.” in English.

3. Results

3.1. Taxonomy

Genus Brachynemurus Hagen, 1888.

Brachynemurus Hagen, 1888: 34 [8]. Type species: Myrmeleon longicaudus Burmeister, 1839 [20] designated by Banks 1899: 70 [21], as B. longicaudus (Burmeister, 1839: 994) [19].

Brief diagnosis. Brachynemurus may be distinguished by the following characteristics proposed by Stange [6,10]: hindwing with narrow posterior area and CuP with more than 10 crossveins to the posterior margin of the wing; male fourth abdominal tergite with a setae on the dark sclerotized band, without microspines (with the corresponding band generally microspinous in Scotoleon) [6,10].

Brachynemurus versutus subgroup sensu Stange [6].

Figure 1, Figure 2, Figure 3, Figure 4 and Figure 5.

Included species. Brachynemurus divisus (Navás, 1927) [22], Brachynemurus elongatus Banks, 1904 [23], Brachynemurus hubbardii Currie, 1898 [24], Brachynemurus versutus (Walker, 1853) [25], and Brachynemurus bowlesi Marquez, Chávez, Tavares, and Contreras, n. sp.

Brachynemurus bowlesi Marquez, Chávez, Tavares, and Contreras, new species.

LSID urn:lsid:zoobank.org:pub:F2BDC141-5236-40F4-86A1-FFC45600C127.

Etymology. We gladly dedicate this species to Dr. David E. Bowles as homage to his brilliant career in entomology, and as a way of thanking him for his kind support through all these years of collaboration (Figure 1A).

Diagnosis. The head is mostly yellow with the interanntenal space brownish to black, the vertex exhibits diffused brown marks, and the antenna is yellowish with brown rings on the flagellomeres (Figure 1B–E). The thorax is yellowish, with some setae appearing thick and black; only the pronotum and scutellum exhibit thin and clear setae, and the pronotum typically presents with two brown longitudinal lines reaching only the distal half (Figure 1B–E). There is a semitriangular mediuncus, dorsally covering the 10th gonostyli, irregularly sclerotized with a small spoon-like cavity (Figure 3F,G). The 10th gonostyli exhibits a laterally widened basal portion, appearing as a square plate, with an irregular dorsal margin, dorsomedially connected to the mediuncus (Figure 3D–G). The 10th gonostyli distal portion is long, broad, and caudally directed, with apical hooks bearing microsetae, and a continuous connection with the basal portion (Figure 3D–G).

Description. Measurements (n = 30, males): Body length: 35.75–37.19 mm; thorax width: 2.65–2.67 mm; forewing length: 20.71–21.96 mm and width: 5.78–5.86 mm; hindwing length: 18.73–19.21 mm and width: 4.30–4.53 mm.

Body color pattern (Figure 1B–E and Figure 2A,B). The color is mostly yellowish, with dark brown marks on the dorsal sclerites and lateral bands on the abdomen; the wing membrane is hyaline, the venation is pale brown, and the pterostigma is white. The rostrum is yellow-white, and the antenna are yellowish.

Head (Figure 1B–E). The color is mostly yellowish, with a dark brown transverse band on the interantennal space and some diffuse marks on the vertex; the scape and pedicel are yellowish, with brown marks on the front part. There are 30–32 flagellomeres, which are yellow with dark rings; the maxillary are pale yellow, but the first and last segments are slightly darker. The galea exhibits modified transparent setae and the labia are pale yellowish, with a rounded and slightly darker sensory area.

Thorax (Figure 1B–E). The color is yellowish, with longitudinal dark brown bands, especially on the terga; there are sparsely distributed whitish setae, as well as fewer short, black, thicker setae. The pronotum exhibits two dorsal longitudinal bands on the posterior half and two thicker ventrolateral bands, with one latero-medial thick seta surrounded by thin, clear setae. The mesonotum and metanotum are yellowish, each with two distinct brown medial bands, and a generally yellowish pleural area, with a few darkened portions.

Legs (Figure 1C,D). The color is yellowish, with abundant black thick setae; the fore and midtibia, as well as the forefemur, exhibit black spots; the tibiae has a transverse black band on the outer face. The tarsomeres show a distal brown ring, longer first and last tarsomeres, tibial spurs, and reddish pretarsal claws, which are as long as the first tarsomere.

Wings (Figure 2). the wings are hyaline, without patterns of variegation, and are long and narrow; the veins and crossveins are alternately brown and white, with a highly setose, acute apex.

Forewing. The forewing is longer than the hindwing, only slightly wide in the second third, with diffused brown spots on the crossveins. The costal area is narrow, but broad at the apex, with more than 27 simple crossveins presenting before bifurcation occurs. The pterostigma are whitish and barely visible, with five crossveins bifurcated at the wing apex. The Sc runs parallel to the RA, until their apex fuses before the wing apex. the subcostal area is regular, without crossveins. The presectoral area of R possesses four crossveins, the RA presents seven branches, and the RP exhibits a conspicuous anterior Banksian line; the hypostigmatic cell is long, with 12 branches, and the distal gradate is well defined. The mediocubital area is slightly broader just before the M bifurcation. The M almost reaches the proximal half of the wing, and the MA bifurcates after the rhegma. The RP fuses with the main branch of CuA, with four branches. The first bifurcation of M not coincident with that of R, but is distant by three crossveins. The Cu has 14 crossveins, with large cells before its fork; the CuA is triangular in origin, with six branches, and irregular crossvein patterns. The CuP is long, almost reaching half of the wing, with 15 branches that are not fused with A at their origin, and with their basal cells as high as the Cu final cells. A exhibits two irregular branches, reaching the first branch of CuP.

Hindwing. The hindwing is lender, with the wing apex more acute than that of the forewing; the disposition of the longitudinal veins is similar to that of the forewing. The pterostigma is whitish or barely visible, with three veins. The costal area is narrow and slightly wide in the middle. The subcostal area is narrow, without crossveins, and is not fused with the RA at the wing apex. The presectoral area has only three crossveins before R. The RA has seven branches, with a well-defined anterior Banksian line. The RP has 11 branches, and makes up 2/3 of the wing length, and the distal gradate is well defined. The mediocubital area is narrow. The M has 12 crossveins, and the cells before bifurcation are as high as the last presectoral cell. The MA exhibits two distal bifurcations, and the MP is fused with the main branch of the CuA, with four branches. The Cu and M bifurcation are almost coincident. The Cu exhibits 14 crossveins before the fork, and the CuA presents six branches, with irregularly arranged crossveins. The CuP has 12 crossveins, with the cells higher than the presectoral cells. The A has only three branches, which are not fused with the CuP.

Abdomen (Figure 1B,C). The abdomen is one and a half times longer than the forewing; it is thin, with the first half pale yellow and the second half darker, exhibiting three longitudinal brown lines dorsally, and is sparsely setose.

Male (Figure 1B and Figure 3). The 8th tergite is rectangular, sclerotized with long setae, and with three barely visible longitudinal lines; the 8th sternum is the same as the 8th tergite, but darker. The 9th tergite is narrowed, sclerotized, and clear, with long setae; 9th sternum is reduced, anteriorly convex, with long setae, and an S-shaped internal hypandrium; the 9th gonostyli is small and curved, with long and thick black setae. The 10th tergite (ectoproct) is ventrally developed, with a posteroventral lobe directed caudally; it is Ivriform, with abundant long and thick setae. The 10th gonocoxite (base of the gonarcus) is simple, narrow, and arched, with the apodemes longer than the distal portion of the 10th gonostyli. The 10th gonostyli is differentiated into basal and distal parts, both with microsetae; the basal portion is laterally widened (square-like) and medially darker with microsetae, and is also connected with the mediuncus. The gonarcus has two positions, contracted and everted, which are more evident in the lateral view. In the contracted position, the 10th gonostyli take a hinge-like position resulting from a fold, causing the basal part to be placed inside the 10th gonocoxite and below the mediuncus, with the distal part of the 10th gonostyli directed caudally and to the outside of the 10th gonocoxite; the 9th gonostyli are raised and lie just below the distal part of the 10th gonostyli. In the everted state, the 10th gonostyli are fully extended and distanced from the 10th gonocoxite, which is more evident in the lateral view. The basal part of the 10th gonostyli exhibits paired short and convergent processes, while the distal part is long–tubular and thickened, with its hooked apices directed laterally. The gonarcus may be manipulated, in alcohol preservation or after KOH clearing, to take either state, possibly because of the articulation of the10th gonostyli. The mediuncus is semitriangular and irregularly sclerotized dorsally, appearing to cover the basal portion of the 10th gonostyli in a contracted state, and is connected with the 10th gonostyli basal portion. The pelta is a small, semioval sclerotized plate, with microsetae.

Female. Unknown.

Ecology (Figure 4A–C and Figure 5A). All specimens were collected at Rancho Agua Nueva, a location comprising livestock areas, secondary grasslands, and primary high semiarid shrubland. Specimens were caught in the afternoon using a net in the grasslands and their surrounding vegetation, and were handpicked at night using a light trap.

Type material: Holotype, male. Mexico: Sonora, Municipio Álamos, Pueblo Yocochihua, Rancho Agua Nueva, 26°45.296′ N, 109°04.299′ W, 165 msnm, 19.ix.2019, Contreras, Barba, Cancino, Ardila, Marquez, [spinous forest, black and white light trap], pinned and dissected, CNIN1929.

Paratypes, Males. Mexico: Baja California Sur, Los Cabos, Sierra de la Laguna, Rancho Ecológico Sol de Mayo, Cabañas, 23°29.899′ N, 109°47.395′ W, 282 msnm, 15.viii.2021, Contreras, Cancino, Luna, Martins, Marquez, 1♂, collected manually, pinned and dissected, CNIN4858./Sonora, Municipio Álamos, Pueblo Yocochihua, Rancho Agua Nueva, 26°45.296′ N, 109°04.299′ W, 165 msnm, 19.ix.2019, Contreras, Barba, Cancino, Ardila, Marquez, 23♂, [xerophilous scrubland, black and white light trap], pinned and dissected, CNIN1873, CAS-CNIN1875, CAS-CNIN1876, FSCA-CNIN1900, FSCA-CNIN1903, MCZ-CNIN1910, MCZ-CNIN1918, NMNH-CNIN1920, NMNH-CNIN1926, TAMU-CNIN1927, TAMU-CNIN1928, CNIN1929, CNIN1932, CNIN1934, CNIN1946, CNIN1948, CNIN1950, CNIN1961, CNIN1964, CNIN1971, CNIN2002, CNIN2003, CNIN2004./Sonora, Arizpe, Barranco del Basaitequi, Rancho las Playitas, 30.5681°N, 110.1036° W, 1261 msnm, 13.vii.2022, T. R. Van Devender, 1♂, [spinous scrubland], in alcohol, dissected, CNIN3151./Sonora, Municipio Moctezuma, Rancho La Montosa, represa, 29°34.201′ N, 109°58.352′ W, 945 msnm, 21.ix.2019, Contreras, Barba, Cancino, Ardila, Marquez, 1♂, [spinous forest, black and white light trap], pinned and dissected, CNIN1863./Sonora, Yécora, Hotel C&C, 28°22′36″ N, 108°05′10″ W, 1529 msnm, 30.vii.2021, Contreras, Cancino, Luna, Martins, Marquez, 4♂, Cupressus forest, [manually collected in light trap], placed in alcohol and dissected, CNIN4859, CNIN4860, CNIN4863, CNIN4864.

Brachynemurus divisus (Navás).

Figure 6A, Figure 7A, Figure 8A,E, Figure 9A–C and Figure 10A,B.

Diagnosis. The head is mostly yellow with brownish to black scars, which are more conspicuous on the interanntenal space. The rostrum and mouth parts are yellowish, the antenna are yellowish with brown rings on the flagellomeres, and the vertex is yellowish with black marks.

The thorax and pronotum are yellowish with submedial and sublateral stripes connected anteriorly with another shorted lateral stripe [6]; the pleural zone is brown with white bristles. The legs are yellowish to amber, with black and white bristles, and all femurs and tibias are dotted. The wings are hyaline and narrow; the apex is acuminate, the pterostigma is black and white, and the forewing is longer than the hindwing. The forewing exhibits altering black and yellow veins, and on the Cu vein, there is a distinct pattern of dots in the crossveins base, which is also observed in the last crossvein of the CuA + CuP and over the rhegma, which continues onto the gradate. The posterior area exhibits interconnected crossveins. The hindwing is similar to the forewing, but the bifurcation of the R and Cu is coincident, without any markings on the membrane.

Abdomen. The abdomen of the male exhibits a brown, well sclerotized 8th tergite and 8th sternum, with a long setae; the 9th tergite is reduced, dorsally divided, and anteriorly convex, with sparce, long setae; the 9th sternum is small, anteriorly concave, and sclerotized with long setae; the ninth gonostyli is membranous and with swollen plates, with long and thick setae, is ventrally located, and very close to the distal portion of the 10th gonostyli. The 10th tergite is narrow, ventrally developed, and shortened, without a postventral lobe; the gonocoxite is arched and narrow, with apodemes reaching the 9th gonostyli; the mediuncus is triangular and extends beyond the gonocoxite, broader basally in the ventrocaudal view. The 10th gonostyli is as long as the apodemes length in the 10th gonocoxite, differentiated into a basal and distal portion, and both portions contain microsetae and are continuous; the basal portion is slightly dark, as are the hooks of the distal portion; in lateral view, the 10th gonocoxite and 10th gonostyli are quite separated and are dorsally connected by the mediuncus. This species is very similar to Brachynemurus elongatus.

Material examined. Mexico: Baja California, San Quintín, Arroyo Cataviñá, 500 m SE Hotel Misión Cataviñá, Carr. 1, 29°43.494′ N, 114°43.016′ W, 521 msnm, 17.x.2023, Contreras, Ramírez, Marquez, Castrejón y De Rosas, 1♂, [UV light, mercury vapor and metallic additives, sheet], placed in alcohol and dissected, CNIN4963./Oaxaca, Dominguillo, 29.xi.1997, S. Zaragoza, 1♂, pinned and dissected, CNIN4929./Oaxaca, 3 mi. West El Camaron, 6.viii.1963, F. D. Parker, L. A. Stange Collectors, 2♀, pinned and dissected, donation of L. Stange, CNIN4150, CNIN4158./Puebla, 3 mi. North Petlalcingo, 03.viii.1963, F. D. Parker, L. A. Stange collectors, 1♂, dissected and pinned, Stange donation, CNIN3164./Puebla, Axusco, Rio Calapa, 4.xi.1988, R. Barba, 4♂, 5♀, pinned and dissected, CNIN4920./Sonora, Municipio Álamos, Pueblo Yocochihua, Rancho Agua Nueva, 26°45.296′ N, 109°04.299′ W, 165 msnm, 19.ix.2019, Contreras, Barba, Cancino, Ardila, Marquez, 23♂, 1♀, [high xerophilous scrubland, black and white light trap], placed in alcohol and dissected, CNIN1836, CNIN1904, CNIN1906, CNIN1908, CNIN1913, CNIN1921, CNIN1922, CNIN1923, CNIN1925, CNIN1930, CNIN1931, CNIN1935, CNIN1936, CNIN1937, CNIN1945, CNIN1947, CNIN1949, CNIN1951, CNIN1970, CNIN1972, CNIN1981, CNIN1990, CNIN1991, CNIN1952.

Distribution (Figure 4A and Figure 5A,B). Mexico: Baja California, Guerrero [6,19,20], Michoacán, Oaxaca, Puebla [6,11,20], Morelos [11,25], Sonora.

Brachynemurus elongatus Banks.

Figure 6B, Figure 7B, Figure 8B,F, Figure 9D–F and Figure 10C,D.

Remarks. This species is quite similar to Brachynemurus divisus, with the main characteristics proposed to differentiate between the species being the presence of interconnected crossveins of the forewing costal area before the pterostigma (in B. elongatus); however, in some examined specimens, both species exhibit the interconnected crossveins in the costal area. Also, bristles on the forecoxa are variable, but following the diagnosis of Stange [6], Brachynemurus elongatus exhibits three to five white bristles, while B. divisus has a variable number of bristles. Nevertheless, in most of the specimens examined, the number and thickness of bristles varies. We decided to consider two species because it was not possible to study the type specimens; however, these two species require a species delimitation study using additional evidence to correctly define their identity, as the morphology of the genitalia of both species is quite similar.

Material examined. Mexico: Baja California, [San Quintín], Angel de la Guarda, 2.viii.85, M. García, 1♀, pinned and dissected, CNIN4162./Baja California, Ensenada, Rancho Mike’s Sky, [roofs and grills near waterfall], 31°05.976′ N, 115°37.302′ W, 1227 msnm, 03.viii.2021, Contreras, Cancino, Luna, Martins, Marquez, 1♂, [light trap], pinned and dissected, CNIN4855./Morelos, Sn. R. Vicente Aranda, 27.viii.1982, Col. H. Velasco, 2♀ (loss of genitalia, but with a long abdomen), pinned, CNIN4160./Puebla, Zapotitl[á]n de las Salinas, Jardín Botánico Helia Bravo Hollis, 06.viii.2019, I. Garzón, 2♂, dissected and pinned, CNIN3186, CNIN4170.

Distribution (Figure 4A and Figure 5A,B). Mexico: Baja California, Chihuahua [6,20], Morelos, Puebla. United States of America: Arizona [6,21,22], California, Nebraska, Nevada [6,22], Colorado [26], New Mexico, Utah [6,21,22,23].

Brachynemurus hubbardii Currie.

Figure 6C, Figure 7C, Figure 8C,G, Figure 9G–I and Figure 10E,F.

Diagnosis. The head is mostly yellow with brownish to black scars, which are more conspicuous on the interanntenal space, the rostrum is amber and the mouthparts are light brown, with some black setae on the clypeus; the antenna are brownish, with lighter rings on the flagellomeres; the vertex is yellowish with diffused brown marks.

The thorax and pronotum are yellowish, typically with four stripes which are nearly connected anteriorly; in some specimens, two longitudinal stripes are discontinued, sometimes only in the posterior half [6]; the pleural zone is brown with white bristles. Following Stange [6], the meron and the forecoxa might vary in color, as the grassland form is pale, and the mountain form can exhibit wide, dark marks; in this study, all specimens belong to the mountain form. The legs are yellowish to amber, with black and white bristles, and all femurs and tibias exhibit small dots. The wings, like those of the B. bowlesi, n. sp. are only semifalcate at the apex.

Abdomen. Eighth tergite and 8th sternum of the male are long, brown, well sclerotized, with long setae; the 9th tergite is reduced, dorsally divided, and anteriorly curved, with sparce setae; the 9th sternum is small, anteriorly concave, and sclerotized, with long setae; the membranous 9th gonostyli presents as swollen plates, with short and thick setae. The 10th tergite is narrow, ventrally developed, and shortened, with a Ivriform postventral lobe; the 10th gonocoxite is arched and narrow, with the length of the apodemes reaching the 9th gonostylus; the mediuncus is semitriangular and fused with the 10th gonostyli; in the lateral view, the mediuncus is the same height as the 10th gonostyli. The 10th gonostyli is slightly shorter than the apodemes of the 10th gonocoxite, differentiated into a basal and distal portion, and both portions have microsetae; however, both appear to begin to divide, or to have a constriction at the boundary of each portion, while the basal portion is slightly dark due to the hooks of the distal portion. In the lateral view, the 10th gonocoxite and the 10th gonostyli are separated.

Material examined. Mexico, Baja California Sur, Los Cabos, Sierra de la Laguna, Rancho Ecológico Sol de Mayo, Cabañas, 23°29.899′ N, 109°47.395′ W, 282 msnm, 15.viii.2021, Contreras, Cancino, Luna, Martins, Marquez, 1♂, [manually collected, light trap], placed in alcohol and dissected, CNIN4858./Sonora, Yécora, Hotel C&C, 28°22′36″ N, 108°05′10″ W, 1529 msnm, 30.vii.2021, Contreras, Cancino, Luna, Martins, Marquez, 2♂, 3♀, Cupressus forest, [manually collected, light trap], pinned and dissected, CNIN4852, CNIN4861, CNIN4862, CNIN4865, CNIN4866. UNITED STATES OF AMERICA, Arizona, Cochise Co., Bisbee, 14 29 Franklyn St., 3.VII.1998, A.S. Menke, 1♀, donation of L. Stange, CNIN4157.

Distribution (Figure 4A and Figure 5A,B). Mexico: Baja California Sur, Chihuahua [25], Durango [6,25], Michoacán, Sinaloa, Sonora, Veracruz, Zacatecas [6,25]. United States of America: Arizona [6,27,28], Colorado [6,26,27], Kansas [6,26,27,28], Nevada, New Mexico [6,27,28], Oklahoma, Texas [6,27], Utah [27].

Brachynemurus versutus (Walker).

Figure 6D, Figure 7D, Figure 8D,H, Figure 9J–L and Figure 10G,H.

Brachynemurus mexicanus Banks, 1895. Synonymy herein revalidated, previously suggested, but not formalized by Banks [12] and Stange [6].

Diagnosis. The head is yellow with large black marks, which are more conspicuous on the interantennal space and epicranial area, extending to the vertex; the rostrum is yellow with three distinct spots, interconnected between the eyes, and two black spots over the mandibles; all these marks might be less or more conspicuous in individuals. The antenna are black or dark brown, with lighter rings on the flagellomeres; the vertex is pale yellow, with transversal black marks interconnected with each other and one black spot behind the eyes.

The thorax and pronotum are pale yellow, with four longitudinal stripes interconnected between each other in the shape of the number eight; the pleural zone is black to dark brown, with some areas of pale yellow, with long, white bristles. The legs are pale yellow with black and white bristles, but the forecoxa exhibits two big black spots, with dots on the femur and tibia. The wings are hyaline and broad, but with a distinct dotted pattern more conspicuous in the forewing; the apex is slightly falcate, the pterostigma is yellowish, and the forewing is longer. In the forewing, the R and Cu bifurcation is almost coincident, the anterior Banksian line is short, but well defined, and the posterior area exhibits some interconnected crossveins; A extends to the first half of the CuP. The hindwing venation is similar to that of the forewing, but the bifurcation of the R and Cu are coincident; the wing membrane exhibits conspicuous spots on the terminal forks.

Abdomen. The abdomen, tergite, and 8th sternum of the male are brown and well sclerotized, with long setae; the 9th tergite is reduced and dorsally divided, with an accurate ventral portion and sparse, long setae. The 9th sternum is small, concave, and anteriorly semidivided and sclerotized, with long and thick setae; the 9th gonostyli is membranous, presenting as plates, with long and thick setae located very close to the distal portion of the 10th gonostylus; they cover the 9th gonostyli in the caudoventral view. The 10th tergite is narrow and ventrally developed, with a lyriform postventral lobe of uniform width; the 10th gonocoxite is arched and slightly broad, with shortened apodemes; the mediuncus is narrow and caudally prolonged, but it does not cover the 10th gonostyli. The 10th gonostyli are longer than the 10th gonocoxite apodemes, differentiated into basal and distal portions, and both portions exhibit microsetae; however, they seem to have a slight division, with the basal portion being slightly dark and elongated, and the distal portion broadened, with ventrally curved darker hooks.

Material examined. Mexico: Estado de México, [Atlacomulco][El Arenal], 18.x.1939, 1♂, pinned and dissected, CNIN4846./Estado de México, Chalma, WlPz colls., 1♀, pinned and dissected, CNIN495./Estado de México, Tequexquino, 19.x.1984, E. González, 1♀, CNIN4955./Guanajuato, Valle de Santiago, Hoya de Alvarez, 20°19′44″ N, 101°12′11″ W, 1847 msnm, 2.x.2008, H. Brailovsky, E. Barrera, L. Cervantes, 1♂, [spinous scrubland], pinned and dissected, CNIN4952./Hidalgo, Tizayuca, Sierra de Pitos, 30.ix.2002, col. J. Gelhaus, 1♂, pinned and dissected, CNIN4159./Jalisco, 14 Km Guadalajara Ruta 54, Posada San Isidro, R. Miller and L. Stange, 22.ix.1986, 1♀, L. Stange donation, CNIN3163,/Oaxaca, Guelatao, 11.ix.1979, E. Mariño, 1♂, pinned and dissected, CNIN4960./Puebla, Acelotla, 23.ix.1994, H. Brailovsky, 1♂, pinned, dissected, CNIN4153./San Luis Potosí, Guadalc[á]zar, 22°36′19″ N, 100°28′22″ W, 1742 msnm, 29.ix.2006, H. Brailovsky, E. Barrera, 1♀, CNIN4154./San Luis Potosí, [Villa de Reyes], Bledos, 1954 msnm, 7–8.x.2009, H. Brailovsky, E. Barrera, 2♂, pinned and dissected, CNIN4156, CNIN4953./Sonora, Municipio Frontera, Sierra Buenos Aires, El Aserradero, 30.7269°N, 109.8211°W, 1707 msnm, 14.viii.2016, J. Palting, T. R. Van Devender, 1♀, [oak forest], pinned and dissected, CNIN3150./Sonora, Yécora, 28°22′43.2″ N, 109°03′00.5″ W, 1690 msnm, 16.x.2004, S. Zaragoza, 1♀, pinned and dissected, CNIN4848./Tlaxacala, [Calpulalpan], Barranca de Calpulalpan, 23.ix.[20]01, col. H. A. Coronel, 1♀, pinned and dissected, CNIN4169.

Distribution (Figure 4A and Figure 5A,B). Mexico: Chihuahua, Durango, Estado de México, Guanajuato, Jalisco, Michoacán [6,25], Distrito Federal/Mexico City, Nayarit [6,25,29], Oaxaca [6,25], Puebla, Sinaloa [25], Sonora. United States of America: Arizona, Colorado [6,27], New Mexico [6,27,30].

3.2. Key to Species of the Brachynemurus versutus Subgroup

1.

The wing membrane is hyaline, with only a few marks on the M and Cu, and the crossveins on the cubital area are interconnected (Figure 2A and Figure 8G); the vertex marks are diffused (Figure 1E and Figure 7C); the thorax pleural zone is mostly yellowish or pale yellow, with some longitudinal stripes (Figure 1C and Figure 8C); the forecoxa, with two small light brown spots, is barely visible or absent on the external face (Figure 1C and Figure 8C).              2

1’.

The wing membrane exhibits either a distinct pattern of spots in specific places or widely scattered spots, with simple crossveins on the cubital area (Figure 8E,F,H); the vertex marks are conspicuous (Figure 7A,B,D); the thorax pleural zone is mostly black, with a few yellowish areas (Figure 8A,B,D); the forecoxa exhibits two big, dark marks or spots on the external face (Figure 8A,B,D).                                             3

2.

The forewing apex acuminates; the pronotum exhibits two longitudinal stripes on the posterior half, which are not interconnected (Figure 1E); the forecoxa is pale yellowish, without marks; the male mediuncus is laterally broad, almost subquadrate, forming a medial roof that covers the basal part of the 10th gonostyli (Figure 3D); the latter basal part is dorsally acute and widely extended laterally (Figure 3F);

                                               Brachynemurus bowlesi, sp. n.

2’.

The forewing apex is semifalcate; the pronotum exhibits four complete longitudinal stripes, which are sometimes basally interconnected (Figure 7C); the forecoxa presents two barely visible brown spots; the male mediuncus is laterally normal, not forming a medial roof-like extension, and the basal portion of the 10th gonostyli is dorsally curved and moderately large, with the latter basal portion reduced laterally (Figure 10E,F);           Brachynemurus hubbardii Currie.

3.

The wings are elongated and narrow, and the pterostigma is black and white, with a distinct mark on the CuA + CuP extending on the final cell of the CuP first fork, along with a second mark on the origin of the MP (Figure 8E,F); the epicranial area exhibits a black mark, without any marks on the frons (Figure 7A,B); the male ectoproct lacks a postventral lobe, and the 10th gonostyli distal part exhibits narrowed hooks.                            4

3’.

The wings are elongated and broad, the pterostigma is yellow, and the whole membrane exhibits scattered dots; the epicranial area presents a large black mark and three connected spots on the frons (Figure 7D); the male ectoproct has a postventral lobe, and the 10th gonostyli distal part exhibits a widened hook (Figure 10G,H); Brachynemurus versutus (Walker).

4.

There is a tuft of white bristles on the outer face of the forecoxa; the membrane is diffused, with the first gradate barely marked and divergent; the male 10th gonostyli distal part shows strongly convex internal flexion, with the differentiation into the basal and distal portions barely conspicuous (Figure 10A,B); Brachynemurus divisus Navás.

4’.

There are white bristles scattered on the forecoxa; the membrane is clear, and the gradates are well defined and parallel; the male 10th gonostyli distal part exhibits internal flexion at an almost obtuse angle, with differentiation into the basal and distal portions evident (Figure 10C,D); Brachynemurus elongatus Banks.

4. Discussion

Brachynemurus, originally proposed with two species [8], later became almost analogous with the Brachynemurini, comprising almost all the currently valid Nearctic genera [6]. It was not until Stange’s reclassification of the Brachynemurini [10] that the genus was defined in its current composition. However, despite its apparent monophyletic status [1], Brachynemurus still lacks reliable synapomorphies and diagnostic characteristics, a difficult task to achieve due to the great structural diversity of the species [6,10]. The most consistent characteristic used to diagnose the genus is the long hind wing CuA, which follows the second branch of the MP fork for a long distance [6,10], although it can be quite short in a few species (such as B. eiseni, B. irregularis, and B. sackeni).

Brachynemurus species of the B. versutus subgroup are similar to each other in general body coloration, and some species have similar wing patterns; however, the frons and pronotum pattern might be useful to differentiate some species from others (Figure 1B–E, Figure 6, Figure 7 and Figure 8A–D; [6]). Therefore, the characteristics of the internal genitalia provide more valuable morphological information to separate species. The 10th gonocoxite—10th gonostylus complex (gonarcus) is quite useful for identifying species in this genus and for diagnosing Brachynemurus bowlesi, n. sp., specifically the shape of the mediuncus and the basal portion of 10th gonostyli (Figure 3D–I). A simple 10th tergite (ectoproct), according to Stange [6], is a useful characteristic to define the subgroup. However, this characteristic is not consistent for the five species of the complex, as Brachynemurus bowlesi, n. sp., B. hubbardiid, and B. versutus, present the development of the postventral lobe of the ectoproct (Figure 3A–C and Figure 9G–L), while Brachynemurus divisus and B. elongatus present a 10th tergite without a postventral lobe, which Stange [6] had previously described as a postventral lobe twice as long as it is wide.

Upon further analysis, it seems that the originally described short postventral lobe in these species [6] might, in fact, be a short, ventrally directed 10th tergite (Figure 9A–F), a unique condition in Brachynemurini, as all other lobeless species (e.g., Austroleon and Chaetoleon) bear a simple, ancestral-like 10th tergite. Structurally similar 10th tergites, also previously described as bearing short postventral lobes, may be found in other Brachynemurini genera such as Scotoleon [2,6], but further studies are needed in order to evaluate whether this is indeed a unique condition for the tribe. Moreover, a postventral lobe on the 10th tergite is a common structure throughout Myrmeleontidae subfamilies [2,31], but no morphological study has been conducted to ascertain the homology of these structures. Markl [31] noted the generalized distribution of these structures through the family, but stated that postventral lobe diagnoses had limited value without precise detailing, while Marque-Lopez et al. [2] discussed and exemplified the structural diversity and importance of the 10th tergite among Myrmeleontidae, but focused on the evolution of the 10th gonocoxite–gonostylus complex (gonarcus).

Brachynemurus bowlesi, n. sp. is similar to B. hubbardii, but they might be differentiated by looking at the shape of 10th gonostyli (Figure 3F and Figure 10E). In B. bowlesi, n. sp., the 10th gonostyli basal part is wider and roof-like in both the contracted and expanded states than it is in B. hubbardii (Figure 3D–I and Figure 10E,F). Brachynemurus bowlesi, n. sp., has an acute 10th gonostyli interior basal portion, while B. hubbardii exhibits a dorsally curved 10th gonostyli basal portion; the 10th gonostyli may even appear to remain dorsally fused in the ventrocaudal view, while in B. bowlesi, n. sp., the 10th gonostyli seems to be divided dorsally (Figure 3F,G and Figure 10E,F).

Regarding the remaining three species (Brachynemurus divisus, B. elongatus, and B. versutus), B. bowlesi, n. sp., exhibits distinct characteristics in regards to both body and genital morphology, as well as in the patterns of the wings, along with the frons and pronotum marking (Figure 6A,B,D, Figure 7A,B,D and Figure 8E,F,H). In males of the B. versutus subgroup, the 10th tergite (ectoproct) bears a noticeably longer and lyriform postventral lobe in B. bowlesi n. sp., B. hubbardiid, and B. versutus, while it is shortened in B. divisus and B. elongatus, so that a postventral lobe appears to be absent (Figure 3A–E and Figure 9G–L). The presence of a postventral lobe on the 10th tergite in these species could be a clue to their relationship; however, the Brachynemurus subgroups proposed by Stange [6] are likely not monophyletic [1] and require further examination in a phylogenetic context in order to properly evaluate their status.

Brachynemurus bowlesi, n. sp. presents a 10th gonocoxite (gonarcus basal component) with a similar size in a wide and arched shape; when compared to other species, only B. versutus presents the 10th gonocoxite with apodemes shorter than those of other species (Figure 3D–I and Figure 10G,H). A wider basal portion of the 10th gonostyli (gonarcus distal component) is a distinct characteristic for Brachynemurus bowlesi, n. sp., along with the association of the mediuncus with the basal portion of these structures, which are discontinuous (Figure 3D–I).

Herein, we revalidate the synonymy of Brachynemurus mexicanus Banks under Brachynemurus versutus (Walker) because both species have the same morphological characteristics and structures, both external and internal, which became more evident when the male genitalia were examined in detail (Figure 11). Previously, Banks [12] had proposed, and Stange [6] had suggested, the possibility that these two species were the same, but Banks [27] again considered B. mexicanus as a valid species. Nonetheless, we detected variations in body coloration, including smaller and darker forms in western Mexico.

We recommend caution whenever analyzing Brachynemurini specimens because of their ability to flex and evert the 10th gonocoxite—10th gonostylus complex, so that the state of the complex changes its perception, and this could cause incorrect taxonomic assignments. Dissecting needles are helpful for checking whether the 10th gonostyli are bent and whether they might be everted caudally.

Brachynemurus species distribution patterns were described previously by Stange [6], in which he proposed 14 provinces based on Brachynemurini species of North America. Regarding species of the Brachynemurus versutus subgroup, they are present in more provinces than those proposed by Stange [6]. Brachynemurus divisus was previously only recorded for central and part of southern Mexico [6]; now we know that this species is also found in northern Mexico in the Pacific Lowlands Province, and that up until to now, its altitude limit has been set at 2500 m.a.s.l., with most records obtained from the Neotropical region (Figure 4A and Figure 5A,B). Brachynemurus elongatus was ranked among the species with the highest altitudinal range for the locations it can inhabit, including the Sierra Nevada and the mountainous areas of the Great Basin [6]. In the present study, B. elongatus indeed shows a Nearctic affinity and a presence in a wide range of provinces with different physiographic features, as well as elevation ranges where they are distributed, extending from approximately 0 m to 2500 m above sea level (Figure 4A and Figure 5A,B). Brachynemurus hubbardii probably has the widest distribution due the three forms detected by Stange [6]; however, with our exhaustive study of the genital characteristics, a new species was proposed herein, which possibly corresponds to the form with a long ectoproct (the 10th tergite with a developed postventral lobe).

Therefore, B. hubbardii, which has a Nearctic affinity, is found at elevations ranging from 0 to approximately 1500 m.a.s.l. and in different provinces (Figure 4A and Figure 5A,B). Brachynemurus versutus occurs in both the Nearctic and Neotropical regions, showing a wide distribution, both in regards to altitude range and the variety of vegetation types. This species may be found even in the highest regions of both Mexico and the United States [6]. Brachynemurus bowlesi, n. sp., has a Nearctic affinity, and it is currently present in four provinces, Baja Californian, Sonoran, Chihuahuan, and Pacific Lowlands, and does not exceed 1500 m.a.s.l. (Figure 4A and Figure 5A).