1977] 
Eberhard — Behavior of Golofa porteri 
295 
the opponent’s grip on the stalk and then pry him away from it, 
hold him briefly between the winner’s head and prothoracic horn, 
and drop him. In some cases neither beetle was lifted completely 
free, but there was a clear winner, and the loser turned and walked 
away. 
In most battles, of course, the chain of events was not this simple 
because each beetle resisted the other’s attempts to dislodge him, 
and the result was often a confusing tangle of legs and horns. 
Periodic violent thrusting and lifting motions of the head horns 
occurred, sometimes accompanied by ripping motions of the front 
legs and sometimes not; of fifteen clear thrusts in filmed sequences, 
seven were immediately preceded by a ripping movement, five were 
probably preceded by ripping, two were not preceded by ripping, 
and one was unclear. Occasionally a beetle raised his front legs 
suddenly during the grappling between thrusts, and then held them 
in the circle position adopted at the start of encounters (Fig. la). 
This movement could conceiveably serve as a defense against en- 
circlement by the opponent’s front legs, and in this case the large 
lateral tibial spines might serve to catch his legs. The leg inter- 
changes between beetles were so variable, however, that it was not 
possible to be certain of these functions. 
Figure 1. Stages in a struggle between two male G. porteri, drawn from frames 
of movie film taken at 30 fps (arrows indicate movement by showing positions of 
legs, etc. in the next frame), a) The upper male has encircled the stalk with his front 
legs. In the next frame he made an apparent threat by abruptly raising his legs 
slightly, and then (in the following frame) lowering them again, b) Each beetle has 
inserted his lowered head horn under the opponent, and, while holding the stalk 
tightly with his middle and hind legs, is “embracing” the opponent with his front 
legs (note how the elongate legs just fit the length of the other beetle’s body), c) The 
lower beetle has just executed the ripping motion with his front legs, dislodging his 
opponent’s left middle and hind legs, and is about to (next frame) flex his head 
dorsally to pry the opponent away from the stalk. His head horn was not under 
the central part of the upper beetle’s body but was somewhat to the right (as seen 
in the drawing), and the attack was not successful since the opponent managed to 
keep his right rear foot hooked to the stalk. (The upper beetle’s left middle and 
left rear legs were out of the focal plane, and their positions are estimated in the 
drawing from shadows cast on the stalk and from other lifting sequences. The 
lower beetle’s head horn was not distinguishable in the next frame, presumably be- 
cause it was moving so fast, but was clear (the head flexion had finished) in the 
following frame; its movement (arrow) was estimated by halving the distance be- 
tween its position prior to and after the flexion.) 
