Corthylus spinosulus Atkinson, 2020

Atkinson, Thomas H., 2020, New species, new records and synonymy of Mexican Corthylus Erichson, 1834 (Coleoptera: Curculionidae: Scolytinae), Insecta Mundi 2020 (792), pp. 1-25 : 2-6

Corthylus spinosulus Atkinson , new species

Fig. 2 A–D; Fig. 3 A, B

Diagnosis. This species would key out to couplet 43 in Wood’s 1982 key along with C. spinosus Wood ( Fig. 3 C–D). An additional species, C. spinipennis Wood (2007: 850) , was described from Costa Rica after 1982 and would also key to the same couplet ( Fig. 3 E–F). All three species share the character of large, acute denticles on the elytral declivity. The species described here is larger than the other two, has an elytral declivity that is more gradually rounded in lateral profile, and has proportionately smaller and less acute denticles on the declivity. All three species are known only from their unique holotypes, a female for C. spinosulus and males for C. spinosus and C. spinipennis ( Fig. 3 ).

Female. Length: 2.70 mm, maximum width: 1.14 mm; length of elytra: 1.65 mm; length to width: 2.4; elytral length/total length: 0.618; elytral length/width: 1.45. (n = 1). Color dark brown, slightly paler at base of elytra.

Frons evenly concave from epistoma to vertex, weakly impressed longitudinally in middle up to a low, blunt elevation at upper level of eyes. Surface shallowly, densely punctured throughout. Vestiture of short, yellowish setae, uniform in length over entire concavity, without longer fringes at the sides or vertex. Antennal club slightly asymmetrical, 1 st suture septate, 2 nd marked by an external groove. Well-developed cirrus of reddish-brown setae, not exceeding the width of the club.

Anterior margin of pronotum rounded, unarmed. Asperities low, small, reduced to impressed lines at summit. Disc of pronotum smooth, shining. Shallow punctures widely separated by more than 5x the diameter of punctures.

Striae and interstriae on elytral disc not impressed, punctures shallow and confused, without associated setae. Declivity evenly rounded in profile. A well-developed, elevated marginal crest extends from the declivital suture to about interstriae 4, about 10% of the declivital circumference. Striae poorly defined on declivity, with strial and interstrial punctures confused. Declivital interstriae 1 slightly elevated (but not costate) with 5 widely spaced blunt tubercles, these increasing in size posteriorly. Interstriae 2 weakly impressed, punctures confused, with a blunt tubercle near the apical margin. Interstriae 3 weakly elevated, with 4–5 blunt tubercles, these slightly larger than those on interstriae 1. Additional smaller tubercles on interstriae 5 on declivital face.

Male. Frons flattened, slightly impressed at epistomal margin. Surface of frons without setae, with widely spaced punctures. A sparse row of setae just above epistoma. Antennal club widened distally.

Pronotum and declivity similar to female. The allotype male has several small denticles on the upper portion of interstriae 2 that are not present in the holotype female. Without more specimens it is not clear whether or not this is a sexual difference.

Type material. Holotype female. Mexico: Chiapas, Chiquihuites , 15.09 N, 92.0798 W, 1,700 m, 5–11-V-2013, flight intercept trap with ethanol and methanol, F. Infante ( CNIN) . Allotype male. Same data except 3-XII-2013, UFFE:12087 ( UFFE in ethanol) .

Etymology. The species name is chosen to indicate the similarity to C. spinosus Wood.

Species with third declivital interstriae serrate and displaced mesally towards suture

Fig. 3 G, H ; Fig. 4 A–H.

The following four species have the third declivital interstriae strongly elevated with prominent granules giving a serrate appearance. These interstriae are in the “normal” position at the base and apex of the declivity but strongly displaced mesally towards the elytral juncture in the center of the declivity. The degree of displacement is so pronounced in several of these species that the elevation appears to be on the second interstriae ( Fig. 4 , A–F). These species would key out to couplet 40 in Wood’s 1982 key but would not go further. They would key to couplet 87 in his 2007 key but would not progress beyond this point. The declivity in these species resembles that of C. senticosus Wood ( Fig. 3 , G, H), but the female frons is totally different and the depth and size of the punctures on the disc of the declivity is much less pronounced. In the three of the four species described here the female frons is convex with no pubescence or surface features in the lower portion and with short, straight setae along the upper and lateral margins; in C. senticosus there are large, yellow spongy areas occupying most of the frontal concavity, a prominent elevation above the epistoma, and a recurved margin of long hairs along the vertical margin ( Wood, 1986: 271). The female of C. poblanus is not known.

Figures

Figure 2. Corthylus spinosulus, new species, female holotype. A) Dorsal habitus. B) Lateral habitus. C) Frons and antenna. D) Declivity. All photographs by the author.

Figure 3. Species of Corthylus with acute spines on declivity or with interstriae 3 curved and serrate (1 of 2). A, B) C. spinosulus, new species, holotype. C–D) C. spinosus Wood, holotype. E, F) C. spinipennis Wood, holotype. G, H) C. senticosus Wood, holotype. Photographs A–B by the author, C–H by S.M. Smith (Copyright National Museum of Natural History, Smithsonian Institution, Washington, D.C., published by permission).

Figure 4. Species of Corthylus with acute spines on declivity or with interstriae 3 curved and serrate (2 of 2). A, B) C. cristatus new species, holotype. C, D) C. cristatulus new species, holotype. E, F) C. granulocristatus new species, holotype. G, H) C. poblanus new species, holotype. All photographs by the author.