Boreocanthon ateuchiceps ( Bates, 1887 )

Edmonds, W. D., 2022, Taxonomic review of the North American dung beetle genus Boreocanthon Halffter, 1958 (Coleoptera: Scarabaeidae: Scarabaeinae: Deltochilini), Insecta Mundi 2022 (952), pp. 1-65 : 28-31

Boreocanthon ateuchiceps ( Bates, 1887) , restored generic combination

Fig. 36–45

Canthon ateuchiceps Bates 1887: 35 .

Boreocanthon ateuchiceps (Bates) (new combination per Halffter 1961: 234).

Canthon (Boreocanthon) ateuchiceps Bates (new combination per Howden 1966: 727).

Boreocanthon ateuchiceps (Bates) , restored generic combination.

Type material. Syntype (sex undetermined). The Natural History Museum, London. Not examined.

Type locality. Acapulco ( Mexico).

Diagnosis. Head: Rugose anteriorly, coarsely punctured posteriorly, punctures denser centrally ( Fig. 37 ). Clypeus quadridentate; paraocular notch conspicuous, setting off salient, rounded angle of paraocular area. Labio-gular fimbria broadly, shallowly V-shaped, apex followed by loose field of coarse, setose punctures. Prothorax: Pronotum evenly covered by variable-sized, sharp, well-spaced punctures on highly shiny background, background shagreen largely effaced ( Fig. 38 ); anterior angles only weakly upturned, posterior portion of circumnotal ridge entire, not serrate, posteromedian angle not depressed. Hypomeral carina present, reaching one-fifth distance to lateral prothoracic margin ( Fig. 40 ). Pterothorax: Mesoventrite coarsely punctured medially, smooth laterally. Metaventrite evenly, sparsely covered by multi-sized, sharp, fine punctures. Elytra: Interstriae ( Fig. 39 ) very shiny, smooth, bright, 2 nd and 3 rd not swollen anteriorly; discal interstriae with ill-defined, scattered, minute punctures, shagreen background largely effaced. Striae superficial, lateral margins weakly defined; subhumeral (8 th) stria finely carinulate; epipleural (9 th) stria usually weakly evident at least anteriorly. Legs: Inner margin of protibia not offset; spur sexually dimorphic, acute apically in female, bifurcate in male. Hind femur lacking anterior row of conspicuous setae. Abdomen: Pygidium with sparse, shallow punctures on shagreen background. Last (6 th) ventrite punctate medially; ventrites 1–5 smooth. Genital capsule: Distal portion of parameres triangular ( Fig. 41 ), lower apical angles in form of elongate, rounded knobs ( Fig. 42 ). General: Dorsum bright metallic green or yellow-green; venter colored similarly except ventrites 1–5, which are black. Length: 4.5–7.0 mm. Geographic distribution: Sierra Madre del Sur, Mexico? ( Fig. 45 , see Comments below). Ecogeographic environment: Tropical Dry Broadleaf Forest biome? Specimens examined: 4.

Collection localities. See Comments below.

Comments. Howden (1966) likened this species to B. forreri , while Bates (1887) placed it near Canthon deyrollei Harold. I do not consider it particularly close to B. forreri ; it is an outlier species both morphologically and geographically, but, given especially the form of the clypeus and genital capsule, definitely a Boreocanthon . Canthon deyrollei is a Central American species only remotely related to Boreocanthon . Boreocanthon ateuchiceps is the only brightly metallic-colored member of the genus; the color of B. forreri (q.v.) is much darker, approaching black in some specimens.

My knowledge of this species is very limited. I have been able to directly examine only four specimens labeled “Matamoros Pue. Tlacotli 8-ix- 43 F. Islas” collected almost 80 years ago by Federico Islas. I have not been able to identify “Tlacotli” nor confirm that “Pue” means Puebla, and I can only guess that Islas’ reference to “Matamoros” is to the Pueblan city or municipality of Izúcar de Matamoros. Howden (1966) mentioned seeing specimens from the states of Guerrero and Mexico in The Natural History Museum (London); I have confirmed their presence there thanks to photographs provided by Max Barclay. Most are labeled “Tejupilco, Mex., Temascaltepec” and “Bejucos, Mex., Temascaltepec”. Each of these two towns is the seat of its own eponymous municipality in the state of Mexico, and both are located on the same highway (No. 134) descending southwest from the city of Temascaltepec into the Balsas River basin in southern Mexico. The type, also in London , bears the label “Acapulco, Guerrero Höge.” Others there bear the same Islas label as those accompanying specimens I have seen courtesy of Gonzalo Halffter. Islas (1942) himself cited it from “tierra caliente de Guerrero,” with no mention of any Puebla locality or Acapulco. Given what little I know, my best guess is that this species is a scarce denizen of the Sierra Madre del Sur, perhaps descending into the Río Balsas valley.

Figures

Figure 45. Approximate distributions of Boreocanthon melanus (Robinson), B. forreri (Bates) and B. ateuchiceps (Bates).

Figures 36–44. Boreocanthon and Canthon spp. 36–42) Boreocanthon ateuchiceps (Bates). 36) Habitus, dorsal view. 37) Dorsal view of head and pronotal margin. 38) Dorsolateral view of pronotum. 39) Dorsolateral view of anterior portion of left elytron. 40) Ventral view of left hypomeron (arrow indicates hypomeral carina). 41) Lateral view of genital capsule. 42) Apical view of parameres. 43) Canthon floridanus Brown (= Canthon imitator auct.). a) Lateral view of genital capsule. b) Apical view of parameres. 44) Canthon (Bajacanthon) obliquus (Horn). a) Lateral view of genital capsule. b) Apical view of parameres.