W. L. Distant, in Biologia Centrali-Americana (1880-1893) stated that in this genus the fore-coxae are spined, and that in males the anterior lobe of the pronotum is swollen.
He also stated that there is little difference between Fibrenus globicollis and F. gibbicollis except that the former species is smaller.
Another stated difference is that in F. gibbicollis the posterior lobe of the pronotum is red-margined at the rear, or may be all black, while in F. globicollis this lobe is generally all-red.
As for range, Distant stated that F. gibicollis had been collected in the Yucatán of Mexico and in Belize, while F. globicollis had been reported from Panama to Brazil.
Photo notes: The bug shown here was feeding on a Cecropia leaf. The photos were made on 19 December 2014, near Leona Vicario, Quintana Roo, Yucatán Peninsula, Mexico.
American Insects site