Canthon (Boreocanthon) mixtus Robinson, 1948

Edmonds, W. D., 2018, The dung beetle fauna of the Big Bend region of Texas (Coleoptera: Scarabaeidae: Scarabaeinae), Insecta Mundi 642, pp. 1-30 : 7-8

Canthon (Boreocanthon) mixtus Robinson

Fig. 33

Diagnosis. Black with strong blue highlights revealed under strong light. Small, length 3–5 mm. Clypeus strongly quadridentate. Pronotum finely but not densely punctate, elytral interstriae with shining spots in place of punctures. Subhumeral stria usually carinulate; tip of pygidium usually more convex than remainder of surface. A formal discussion of this species appears in Halffter (1958).

Big Bend collection sites (altitudinal range: 1010–1630 m [2310 m in Sierra El Carmen]).

Brewster Co.: [1] ~ 17 km W Alpine ( Paisano Baptist Encampment ), 30°17′37″N 103°47′35″W, 1550 m (Jul) ;

Jeff Davis Co.: [1] 16 km S Fort Davis (along TX 17), 30°27′48″N 103°58′59″W, 1600 m (Aug) ; [2] ~ 16 km NE Valentine, Muerto Springs Ranch ( Muerto Springs , near headquarters), 30°40′28″N 104°24′07″W, 1475 m (Jul) ; [3] 8 km SE Fort Davis (via TX 118 ), Chihuahuan Desert Research Institute ( Visitor Center area), 30°32′32″N 103°50′11″W, 1555 m (Aug) ; [4] Chihuahuan Desert Research Institute ( Quarry Unit ), 30°32′06″N 103°50′37″W, 1480 m (Aug–Sep) ;

Presidio Co.: [1] C.E. Miller Ranch (~ 16 km W Valentine), 30°32′50″N 104°39′40″W (Camp Holland) 1410 m (Aug) ; [2] ~ 16 km W Valentine ( Miller Ranch , near headquarters), 30°33°30″N 104°38′44″W, 1350 m (Jul–Aug); [3] ~ 6.5 km W Marfa (Hip-O Ranch), 30°21′54″N 104° 7′12″W, 1530 m (Aug–Sep); [4] Pinto Canyon Ranch (~ 58 km SSW Marfa on FM 2810 ), 30°01′18″N 104°27′42″W (headquarters area), 1475 m (Aug); [5] Dalquest Research Site, 29°33′30″N 103°47′30″, 1010 m [Sep] ; [6] 37 km SSW Marfa (along FM 2810 , Petan Ranch – Cherry Hills sector), 30°07′35″N 104°19′24″W, 1630 m (Jun) ; [7] 20–26 km SSE Marfa (along FM 169 ), 1355–1415 m (Jun) ; [8] 3 km NE Marfa (along FM 1112 ), Marfa Golf Course, 30°19′40″N 103°59′41″W, 1470 m (Jul, Sep) ; [9] ~ 30 km SSE Marfa (along FM 169 ), Humphreys Ranch , 30°02′30″N 104°01′00″W, 1285 m (Jul) ; [10] ~ 8km W La Viuda Peak , 29°42′30″N 103°54′30″, 1200 m (Sep) ; [11] ~ 19 km E Marfa (via US 90/67), 30°16′07″N 103°48′44″W, 1565 m (Jul) ; [12] ~ 3 km N Marfa (along TX 17 ), 30°20′27″N 104°01′7″W, 1500 m (Jul) ; [13] near Plata ( FM 169 / Alamito Creek bridge) Kennedy Ranch (headquarters), 29°52′16″ N 103°59′28″ W, 1200 m (Jun) ; [14] Pinto Canyon Ranch (~ 65 km SSW Marfa on FM 2810 ), 29°59′54″N 104°30′48″W (Pinto Canyon Creek), 1460 m (Aug) .

MEXICO: Coahuila, Sierra El Carmen ( Maderas del Carmen ), 28°59′54″N 102°36′ 42″ W, 2310 m. (Jul) .

Collection method(s). a) baited pitfall trap (human feces); b) direct capture (cow dung).

Surface activity. Diurnal.

Habitat. Grasslands and open areas in desert scrub.

Comments. Canthon mixtus , whose type locality is Marfa, appears to be a near-endemic to the Big Bend portion of the Chihuahuan Desert, but its occurrence in coniferous forest at high altitude in the Sierra El Carmen is quite unexpected. It is similar to C. melanus , reported from El Paso Co. ( Riley and Wolfe 2003), which has a shallow, obtuse (rather than deep, acute) clypeo-genal notch; moreover, the tip of the pygidium is neither shinier nor more convex than the remainder of the surface. Canthon melanus is a common species in southwestern Arizona, where C. mixtus is absent.

Figures

Figures 26–35. Canthon. 26) C. imitator, dorsal view, male. 27) Same, ventral view of abdomen. 28) Same, ventral view of female abdomen. 29) C. blumei, dorsal view, female. 30) Same, oblique dorsal view of forebody. 31) Same, ventral view of right propleuron (arrow marks transverse carina). 32) C. imitator, ventral view of right propleuron. 33) C. mixtus, dorsal view, male. 34) C. praticola, dorsal view, female. 35) Same, oblique view.