Canthon (Canthon) blumei Halffter and Halffter

Edmonds, W. D., 2018, The dung beetle fauna of the Big Bend region of Texas (Coleoptera: Scarabaeidae: Scarabaeinae), Insecta Mundi 642, pp. 1-30 : 6

Canthon (Canthon) blumei Halffter and Halffter

Fig. 29–31

Diagnosis. Black, only rarely with even subtle hint of blue. Dorsum completely, densely covered by small granules on field of fine shagreening. Clypeus bidentate, teeth acute, separated by rounded emargination. Elytral striae fine, superficial, almost effaced posteriorly. Propleuron divided by sharp, transverse carina extending from procoxa to lateral margin ( Fig. 31 , arrow). A formal description of this species appears in Halffter and Halffter (2003; as C. humectus blumei ; raised to species status in Halffter et al. 2015).

Big Bend collection sites (altitudinal range: 1480–1555 m).

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] Davis Mountains State Park, Limpia Canyon Research Area , 30°36′5″N 103°55′34″W, 1525 m (Jun, Aug) ; [2] 16 km S Fort Davis (along TX 17 ), 30°27′48″N 103°58′59″W, 1600 m (Aug) ; [3] ~ 16 km NE Valentine, Muerto Springs Ranch ( Muerto Springs ), 30°40′50″N 104°20′22″W, 1555 m (Jul) ; [4] Chihuahuan Desert Research Institute ( Quarry Unit ), 30°32’06”N 103°50′37″W, 1480 m (Aug–Sep) ; [5] ~ 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) .

Presidio Co.: [1] 6 km ~ 6.5 km W Marfa (Hip-O Ranch ), 30°21′54″N 104°07′12″W, 1530 m (Aug–Sep) .

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

Surface activity. Diurnal.

Habitat. Primarily montane woodlands, occasionally open grassland.

Comments. Canthon blumei was originally described as a subspecies of C. humectus occupying the southern and western parts of Texas; it was raised to species status by Halffter et al. 2015. The remaining populations of C. humectus comprise a widely distributed Mexican species complex whose range covers most of the Mexican Altiplano ( Halffter and Halffter 2003; Halffter et al. 2015) and which are the subject of ongoing evolutionary studies by Gonzalo Halffter and his associates. Canthon blumei is similar morphologically and ecologically to C. imitator , both of which are common in the Big Bend area. In contrast to C. imitator , which is abundant in the open grasslands, this species displays a distinct preference for montane wooded habitat. They can be captured together, but the relative frequencies of the two are strikingly different depending upon habitat. In the Quarry section of the Chihuahuan Desert Research Institute property near Fort Davis, a typical wooded montane habitat ( Fig. 21 ), an August 2008 48-hr baited pitfall trap captured 192 C. blumei and only two C. imitator , and a contemporary trap in somewhat higher and more open montane habitat near the visitors’ center yielded 336 C. blumei and 31 C. imitator . In lower, open grassland, these ratios switch to strongly favor C. imitator , often in the absence of C. blumei (see Introduction).

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.

Figures 19–25. Big Bend montane habitat. 19) Seasonal creek, Quarry section, Chihuahuan Desert Research Institute (wet season). 20) same, dry season. 21) Woodland/meadow enclave in summer, Quarry section, CDRI (Jeff Davis Co.). 22) Davis Mountain woodland (Jeff Davis Co.). 23) Same. 24) Box Canyon, Miller ranch (Presidio Co.). 25) Same, interior view.