Wilcoxia James, 1941

Pollock, Darren A. & Reichert, Lisa A., 2019, Review of the Nearctic genus Wilcoxia James (Diptera: Asilidae: Stenopogoninae) with descriptions of three new species, Zootaxa 4695 (5), pp. 401-437 : 402-405

Wilcoxia James

Wilcoxia James, 1941 . Type species, by monotypy and original designation: W. cinerea James, 1941 ; Wilcox & Martin 1957: 2 [key to related genera]; Hull 1962 a, b: 122 [in key to genera of Stenopogonini ], Figs 82 (antenna), 585 (wing), 980 (frontal view of head); Martin & Wilcox 1965: 385 [catalog of Nearctic Diptera ]; Wilcox 1972: 43; Wood 1981: 569 [key to Nearctic genera]; Papavero 1973: 248 [in list of genera in subfamily Stenopogoninae ]; Artigas & Papavero 1991 a: 142 [in list of tribes and genera of American Stenopogoninae ]; Artigas & Papavero 1991 b: 57 [in key to genera of Stenopogoninae : Cyrtopogonini ]; Poole & Gentili 1996: 64.

Notes. James (1941) did not provide a description of his new genus, but a relatively detailed description was given for W. cinerea , then the only included species. Hull’s (1962 a) description of the genus was more complete than that of James (1941) but was probably also based on only W. cinerea . However, in the captions for the four figures de- picting a species of Wilcoxia in Hull (1962 b) , only one of these includes W. cinerea ; the other three merely list the illustrated specimen as Wilcoxia sp.

Poinar (1992) illustrated a robber fly from Dominican amber (Oligocene/Miocene), called a Wilcoxia in the caption. This has led to the genus being included in the Neotropical region (e.g. Papavero 2009, as Wilcoxia sp.). The specimen on which this identification was based is deposited in the American Museum of Natural History (Poinar, pers. comm.). According to Eric Fisher (pers. comm.) who has examined this amber inclusion, a preliminary identification of “ Wilcoxius sp.” by him was misinterpreted by Poinar and given instead as “ Wilcoxia sp.”. Wilcoxius is a Neotropical genus in the Asilinae.

Species groups.—As discussed below, when Wilcox (1972) described four new species of Wilcoxia , the genus became structurally heterogeneous; however, the presence of the distinct mesotibial spine seems to have been considered a diagnostic feature for the genus. Though this structure is found in all species currently in Wilcoxia (including the three new species described herein), we have observed other characters that seem to divide the eight species into two species groups. We have not established new subgenera or a new genus (for the martinorum group), but rather suggest that this might be a necessary action in the future based on further study including phylogenetic analysis. Structural features which divide the species into the two species groups ( cinerea and martinorum ): relative length and angle of projection of dorsocentral hairs and setae on the scutum; number and angle of projection of marginal setae on scutellum; “crinkliness” of katatergite setae; pattern of pollinosity on abdominal tergites; and color of legs. Another observation included here is the tendency for specimens of the two different species groups to be collected either relatively early or late in the year. No Wilcoxia collections are known from March to May, and specimens have been collected on only one day in both February and June. The four species in the cinerea group were collected from June to October (only a single specimen in October), while the four species in the martinorum group were collected from October to February ( Table 1 ).

Description. Small robber flies, body length, excluding antennae from 4.4–9.9 mm; wing lengths from 4.3–6.9 mm. Head ( Figs 17–25 ). Width 1.5–1.7 times eye height; face pollinose, very short, in profile at, or slightly beyond eye margin; facial gibbosity only slightly developed; sides of face very slightly to moderately converging toward antennae; frons pollinose, subparallel-sided to moderately diverging towards vertex; compound eyes relatively large, occupying almost entire height of head; posterior margins evenly arcuate or slightly angulate (esp. so in martinorum group); anterior facets distinctly enlarged; ocellar tubercle very slightly to moderately elevated, bearing short and longer setae; median ocellus larger than lateral ocelli; occiput densely pollinose, flat to moderately convex, dorsally with long, postocular bristles, ventrally bearing occipital hairs of various lengths and densities (the latter esp. well developed in martinorum group, Figs 21–25 ); mystax variable, occupying lower half of face in some species, in others occupying entire face, especially long and dense in martinorum group species (e.g., Figs 21, 23 ); face above mystax with smaller, appressed hairs; proboscis laterally slightly compressed, blunt apically; palpi 2-segmented, distal palpomere distinctly longer than proximal; antennae inserted slightly above middle of head, antennal bases not on raised area; insertions approximate, separated by scape width or less; scape and pedicel short, subequal in length, with various number of short and/or long setae; scape subfiliform, parallel-sided; pedicel submoniliform, slightly to moderately widened distally; postpedicel elongate, longer than scape and pedicel combined, parallelsided for at least ½ length, then slightly to moderately tapered apically; style 2-segmented, first much shorter than second, but of equal widths; second stylomere with short slender spine; antennae pollinose, some species with bare scape (sometimes just the medial surface).

Thorax. Entire surface pollinose; ante- and postpronotum with variable number of setae; scutum moderately convex; most species with divided median stripe between 2 rows of acrostichal bristles; surface uniformly pollinose, some species with one or more elliptical bare spots or spots with contrastingly colored tomentum, on each side of midline; vestiture of scutum various, some species with long presutural setae, others with very short setae, with any longer setae restricted to postsutural area of scutum; notopleural, supraalar and postalar bristles present, variable in number (from 1–3); anepisternum and katepisternum without setae; katatergite bearing variable number of long setae, apices either “crinkly” ( martinorum group, e.g. Fig. 43 ) or not ( cinerea group, e.g. Fig. 44 ); anterior surface of procoxae and lateral surfaces of meso- and metacoxae with elongate hairs; scutellum slightly convex, entire surface pollinose in some species (e.g., Fig. 41 ), in others, with posterior margin shining, non-pollinose (e.g., Fig. 42 ); disc of scutellum with or without scattered, short hairs; posterior margin with longer setae, the angle compared to plane of scutellum ranging from nearly parallel to perpendicular, setae either parallel to each other, or distinctly converging medially.

Legs relatively slender, similar in proportions among pairs; color uniformly dark (piceous to black) ( martinorum group, Figs 9–16 ) or with contrasting dark and yellow areas ( cinerea group, Figs 1–8 ); hind leg moderately longer than anterior two pairs; peg-like protuberance present on anterior face of metacoxae; femora relatively slen- der, elongate, variously swollen in proximal half, or subparallel; surface of femora bare ( cinerea group), pollinose, or a combination of the two (spp. in martinorum group), covered with scattered, appressed short hairs and longer, erect setae; dorsal apex of femora with or without one to several stout setae/bristles; tibiae slender, straight, subequal in length to femora; surface with combination of short, appressed hairs and longer setae/bristles, similar on all legs (male W. apache with anterior tibial hairs much longer than on other legs); apex of front tibiae without or with ( W. painteri only) short, slightly sigmoidal spine ( Fig. 45 ); ventral apex of middle tibiae with stout spine/bristle ( Fig. 46 ), in most species darker than regular tibial bristles; tarsi 5-segmented, relatively slender, more robust in some species, middle tarsomeres submoniliform; length of tarsus subequal in length to tibia; hind tarsus, at least in male, more robust than front or middle tarsus; brush of setae on first tarsomere somewhat denser on hind tarsus; length of tarsomere 1 subequal in length to 2 + 3; apex of each tarsomere with circlet of relatively long, stout bristles; tarsal claws fine and sharp, widest basally, then abruptly narrowed, distinctly curved apically; pulvilli long, slender, almost as long as claws; empodium slender, about half length of tarsal claw.

Wing ( Figs 38–40 ) immaculate, hyaline to moderately darkly infuscated brown, color slightly sexually dimorphic (darker in males) in some species of cinerea group; costa (C) complete around posterior margin to wing base, except in W. forbesi , in which it stops near junction of CuA 2 + A 1 ( Fig. 38 ); vein R 2+3 ending in C, apex very slightly directed forward before C; R 4 and R 5 only slightly arcuate; r-m crossvein beyond midlength of discal cell; apical portion of M 3 at approximately right angle to m-m crossvein; A 1 and CuA 2 meeting at margin or with slight gap; cell m 3 broadly open at wing margin; cell cu p closed or very narrowly open at wing margin; wing membrane either without conspicuous microtrichiae (esp. martinorum group, e.g. Fig. 40 ) or with distal half to third with dense, conspicuous microtrichiae ( cinerea group, e.g. Fig. 39 ).

Abdomen relatively slender, convex dorsally; first segment slightly narrower than width of mesonotum; segments wider than long or subequal in length and width (in W. pollinosa segments 2–4 distinctly longer than wide); males with 7 visible tergites; female with 8 visible tergites, 8 th about half length of 7 th; tergites densely pollinose with bare patches vaguely in “checkerboard” pattern (most martinorum group spp., Figs 30–33, 36–37 ) or mostly bare (most cinerea group spp., Figs 26–29 and female of W. forbesi from the martinorum group, Fig. 35 ) with pollinosity restricted to narrow lateral and/or anterior bands; male and female W. pollinosa ( Fig. 29 ) and male of W. forbesi ( Fig. 34 ) with tergites uniformly pollinose; tergites dorsally with relatively short, sparse setae (relatively longer in spp. of martinorum group), laterally with longer setae, especially on tergites 1–3 (very long in some martinorum group spp.); sternites uniformly pollinose, 6–7 of females of some species bare, non-pollinose; surface of sternites with setae/hairs of various lengths, relatively inconspicuous in some species (especially W. pollinosa ), in others very long ( martinorum group), longer on sternites 1–3 than posterior sternites.

Male genitalia ( Figs 47–57 ) relatively short, inconspicuous, rotated 90–180° in most specimens; genitalia somewhat oblique in lateral view, with dorsal structures protruding more posteriorly than ventral; hypandrium distinct, widest anteriorly, roughly triangular to subtrapezoidal in shape; epandrium divided into two separate lobes, attached posteriorly; cerci short, broadly rounded to subtruncate; gonopod well-developed, consisting of elongate, digitiform gonostylus ( Fig. 53 , gs) and gonocoxite; gonocoxite with relatively robust dorsal ( Fig. 53 , dp) and ventral processes ( Fig. 53 , vp) laterally, and medial process ( Fig. 53 , mp); dorsal process variously bifid (e.g., Figs 53–54 ) or entire; medial process slender, indistinctly to very distinctly apically curved dorsad; phallus ( Fig. 53 , ph) very wide basally, evenly or somewhat abruptly narrowed distally, with or without small denticle ( Fig. 53 , pd) on lateral margins.

Female genitalia. Tergite 10 divided into two acanthophorites, each bearing 4–5 short, slightly curved spines ( Fig. 58 ); spermathecae (based on Figs 37–38 in Artigas and Papavero 1991 b) three in number, very elongate, thread-like.

Natural history. Relevant biocontextual information is generally lacking for most species of Wilcoxia ; specific details are presented below under each species. The best-known species are those in the martinorum group (especially W. apache , new species, given its proximity to Portales, the authors’ town of residence), perhaps because of their tendency to rest on rocky substrates (e.g., Figs 68–72 ) and therefore their relative ease of observation and/or collection. In fact, all known prey associations for Wilcoxia are from the martinorum group: W. apache , new species, W. forbesi , new species, and W. martinorum . It is hypothesized that members of the cinerea group are more closely tied to vegetation and therefore their habits are more difficult to observe.

Figures

FIGURES 17–25. Laterofrontal view of head of Wilcoxia spp. 17. W. cinerea, male. 18. W. monae, male. 19. W. painteri, male. 20. W. pollinosa, male. 21. W. apache, n. sp., male. 22. W. flavipennis, n. sp., male. 23. W. forbesi, n. sp., male. 24. W. forbesi, n. sp., female. 25. W. martinorum, male.

FIGURES 41–46. Figs 41–42. Detail of posterior scutum and scutellum. 41. W. apache, n. sp. showing uniformly pollinose scutellum and many marginal setae as well as the linear, non-pollinose patches on scutum. 42. W. monae, showing posteriorly non-pollinose scutellum and relatively few marginal setae. Figs 43–44. Katatergite setation. 43. W. apache, n. sp. male, with “crinkly” setae. 44. W. cinerea, female, with “non-crinkly” setae. Fig. 45–46. Apical tibial spurs. 45. W. painteri, female, sigmoidal apicoventral spur on front tibia. 46. W. apache, n. sp., male, stout spur at apex of middle tibia.

FIGURES 9–12. Figs 9–10. Male (9) and female (10) paratypes of W. apache, n. sp. Male from Curry Co., NM; female from Chaves Co., NM. Figs. 11–12. Male (11) and female (12) paratypes of W. flavipennis, n. sp. Both specimens from Sonora, Mexico.

FIGURES 13–16. Figs 13–14. Male (13) and female (14) paratypes of W. forbesi, n. sp. Both specimens from Doña Ana Co., NM. Figs 15–16. Male (15) and female (16) paratype of W. martinorum Wilcox. Both specimens from Riverside Co., CA.

FIGURES 1–4. Figs 1–2. Male (1) and female (2) paratypes of W. cinerea James, nr. Saguache, Saguache Co., CO. Figs 3–4. Male (3) and female (4) paratypes of W. monae Wilcox. Male from Douglas Co., NV; female from type locality, Mono Co., CA.

FIGURES 5–8. Figs 5–6. Male (5) and female (6) paratypes of W. painteri Wilcox. Male from Catron Co., NM; female from Kane Co., UT. Figs 7–8. Male (7) and Allotype female (8) of W. pollinosa Wilcox. Male from Chaves Co., NM; Allotype from Eddy Co., NM.

FIGURES 38–40. Fig. 38. Wing of male W. forbesi, n. sp. showing abbreviated costa (not present to wing base). Fig. 39. Apex of wing of male W. pollinosa, showing dense microtrichial field on wing membrane. Fig. 40. Detail of wing of male W. forbesi n. sp. showing lack of conspicuous microtrichiae on wing membrane.

FIGURES 30–37. Abdomens of Wilcoxia spp. (martinorum group), dorsal. 30. W. apache, n. sp., male; 31. W. apache, n. sp., female; 32. W. flavipennis n. sp., male; 33. W. flavipennis, n. sp., female. 34. W. forbesi, n. sp., male. 35. W. forbesi, n. sp., female. 36. W. martinorum, male. 37. W. martinorum, female.

FIGURES 26–29. Abdomens of Wilcoxia spp. (cinerea group), dorsal. 26. W. cinerea, male; 27. W. monae, male; 28. W. painteri, female; 29. W. pollinosa, male.

FIGURES 47–58. Male genitalia (47–57) and ovipositor (58) of Wilcoxia spp. 47. W. cinerea, ventral view (epandrium removed). 48. W. monae, ventral view (epandrium removed). 49–50. W. painteri, ventral and right lateral view. 51–52. W. pollinosa, ventral (epandrium removed) and slightly oblique view. 53–54. W. apache, n. sp., ventral and dorsal oblique view. 55. W. flavipennis, n. sp., ventral view. 56. W. forbesi, n. sp., dorsal view (epandrium removed). 57. W. martinorum, ventral view (epandrium removed). 58. W. apache, n. sp., terminal abdominal segments and ovipositor. dp = dorsal gonocoxite process; dpc = dorsal gonocoxite process carina; gc = gonocoxite; gs = gonostylus; lep = lateral ejaculatory process; mp = medial gonocoxite process; pd = phallus denticle; ph = phallus; vp = ventral gonocoxite process.

FIGURES 67–70. Habitats of Wilcoxia spp. 67. Habitat of W. pollinosa (Chaves Co., NM). Individuals were collected by general sweeping of this diverse vegetation. Unfortunately, no specimens were seen in/on specific plants. 68. Type locality (up on cliff edge) of W. apache, n. sp., Quay Co., NM. 69. Detail of rocky terrain at type locality of W. apache, n. sp., Quay Co., NM. 70. Female of W. apache, n. sp. resting on typical rocky substrate, Quay Co., NM (photo credit: George W. Pollock).

FIGURES 71–76. Habitats of Wilcoxia apache, n. sp. 71. Haystack Mtn., Chaves Co., NM. 72. Near Goose Lake, Muleshoe National Wildlife Refuge, Bailey Co., TX. 73–74. Habitat and individual fly resting on this “atypical” substrate, Muleshoe National Wildlife Refuge, Bailey Co., TX (away from cliff edge seen in Fig. 72). 75–76. Railroad Mtn. Rd., Roosevelt Co., NM. Individuals were seen on the stony substrate and also on the isolated clusters of larger rocks.