Description of unique defensive behaviours of the Radiant Sun Beetle Prionotheca coronata (Tenebrionidae)

Abstract

The defensive behaviours of Prionotheca coronata have not been well-described in the past. This species possesses long, sharp spines along its abdominal margin and along its inner hind legs. When disturbed, beetles frequently assume a defensive posture with their head down, posterior up and rear legs spread apart. Beetles quickly rotate so that their raised posterior faces threats coming from the side. If beetles are touched while in this defensive posture, they will often try to pinch whatever is touching them between the spines of their abdomen and inner rear legs. In trials with 50 beetles, we found that 84% of beetles assumed a defensive posture immediately after being removed from a pit trap and prodded. Beetles rotated left or right 58% of the time if the sand was hit to that side of them, but only 2% of the time if it was hit directly behind them. Beetles attempted to pinch our fingers 78% of the time when they were touched between their abdomen and rear legs, but only 31% of the time if they were touched elsewhere (top, bottom and sides of the abdomen). Their pinch is surprisingly strong, and can rarely draw blood.