Dung beetle horns evolved and were lost repeatedly across their history

Evidence

A second strategy adopted by many dung beetles is tunneling. Females of these species fly into dung and immediately begin to excavate burrows into the soil below. Once they’ve dug sufficiently deeply—a foot to a yard, depending on the species—they begin pulling pieces of dung down into the tunnels to stash them away from the other dung-feeding insects above. … Males of tunneling species often have horns. — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 222 (#corroborates, via linked claim)

Armed with this insight, we can return to the problem of horned and hornless dung beetles. Why do some species produce horns while others feeding on the same resources in the same habitats do not? The answer, I have come to suspect, has nothing to do with the dung and everything to do with what these animals do after they arrive at the dung. — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 218 (#expands, via linked claim)

Categorization

• XREF: connects to: Tunneling dung beetles guard burrow entrances and evolve horns; rollers do not — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 222; Beetle horn presence depends on post-arrival behavior, not the dung itself — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 218; No ball-rolling dung beetle species has evolved horns despite constant fighting (+1 more)

Related

• No ball-rolling dung beetle species has evolved horns despite constant fighting (similarity 0.97)
• Tunneling dung beetles guard burrow entrances and evolve horns; rollers do not (similarity 0.92)
• Beetle horn presence depends on post-arrival behavior, not the dung itself (similarity 0.91)
• Tunneling behavior predicts horn evolution in dung beetles (similarity 0.91)
• Closely related beetle species can differ sharply in horn possession (similarity 0.86)
• Smaller-horned males usually lose escalated dung beetle fights (similarity 0.83)
• Dung beetles offer the ideal study system for extreme weapon evolution. (similarity 0.82)
• Tunnel-bound fights give longer horns a decisive performance advantage (similarity 0.80)
• Tunnel dwellers fight successive duels and evolve weapons; open-ground species scramble without them. (similarity 0.79)
• Beetle horns can be impressively large yet nearly cost-free to produce and use (similarity 0.78)

Broader Connections

• No ball-rolling dung beetle species has evolved horns despite constant fighting #corroborates (0.75)
• Tunneling dung beetles guard burrow entrances and evolve horns; rollers do not #corroborates (0.70) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 222
• Beetle horn presence depends on post-arrival behavior, not the dung itself #expands (0.60) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 218
• Closely related beetle species can differ sharply in horn possession #exemplifies (0.55) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 193