Hylocurus rudis (LeConte, 1876)

Atkinson, Thomas H., 2024, New species, new synonymy, taxonomic notes and new records of bark and ambrosia beetles from the southwestern United States and northern Mexico (Coleoptera: Curculionidae: Platypodinae and Scolytinae), Zootaxa 5424 (2), pp. 151-175 : 160-161

Hylocurus rudis (LeConte, 1876)

Fig. 6 (A–K)

Micracis rudis LeConte 1876: 369

Hylocurus rudis (LeConte) : comb. Blackman 1928: 187

Micracis biorbis Blackman, 1920: 22 : synonymy Wood 1972: 196

Hylocurus torosus Wood, 1971: 28 : synonymy Atkinson 1989: 327

Hylocurus binodatus Wood, 1974: 17 new synonymy

Hylocurus rudis LeConte is found in the southeastern United States and is characterized by an oval, concave depression in the center of the frons with two spongy projections on the dorso-lateral or lateral margins of this concavity ( Fig. 6 ). In some specimens these are inflated ( Fig. 6 C–H ) and in others appear deflated ( Fig. 6 B,J ), suggesting that the structures may be hollow. With optical microscopy these swellings appear paler than the surrounding cuticle and have a very different texture from the surrounding cuticle of the frons, appearing spongy. With SEM photography ( Fig. 6 K , Atkinson 1989) these are shown to consist of densely packed scale-like setae mixed with short conical setae. Wood separated specimens in which the projections are on the ventro-lateral margins of the frontal concavity as H. torosus ( Fig. 6 G ). Isolated specimens are frequently captured in traps but longer series are rare in collections. After examining around 170 specimens from throughout the range it is clear that the position of these projections is highly variable and presents no useful taxonomic information. They may be on the dorsal, lateral, or ventral margins of the frontal concavity. Their size is also variable. Wood (1982) states that the frontal concavity is never carinate in the center. In many specimens it is clear that the concavity is deeper on either side of the center line, and that in many cases a longitudinal carina is evident ( Fig. 6 B, D, F, J ).

Hylocurus binodatus was described from specimens ( Fig. 6 H ) in which the central concavity is shallower that that of “typical” H. rudis and in which the spongy projections are displaced away from the lateral margins towards the interior of the concavity. After examining over 40 specimens identified as H. binodatus it is clear that this character is also quite variable and intergrades with the characters of H. rudis . There are no other significant external characters of the declivity or antennae that would allow separation of two or more species. I have examined all relevant types as well as all specimens in the USNM, including the Wood collection. Only a single species is present.

Figures

FIGURE 6. Variation in position of spongy structures and transverse carina on concavity on frons of Hylocurus rudis (A) Dorsal (Oklahoma), (B) Dorso-lateral, slight carina (Alabama), (C) Upper-lateral (Alabama), (D) Lateral, displaced mesad, carina (Texas), (E) Lateral (Oklahoma), (F) Lateral, slight carina (Texas), (G) Lower-lateral. Holotype Hylocurus torosus Wood (South Carolina), (H) Lower-lateral, displaced mesad. Holotype Hylocurus binodatus Wood (Mississippi), (I) Lower-lateral, strongly displaced mesad, protuberant (Michigan), (J) Dorso-lateral, strong carina (Arkansas), (K), SEM closeup of frontal structure, from Atkinson 1989. G, H. by S.M. Smith, all others by T.H. Atkinson.