FIGHTING BEHAVIOR OF 
MALE GOLOFA PORTERI BEETLES 
(SCARABEIDAE: DYNASTINAE)* 
By William G. Eberhard 
Depto. de Biologia 
Universidad del Valle 
Cali, Colombia, and 
Smithsonian Tropical Research Institute 
P. O. Box 2072 
Balboa, Canal Zone 
Large males of Golofa porteri possess several striking secondary 
sexual characteristics: the head has a long, curving horn with ser- 
rations along its edges; the prothorax has an even longer, thinner, 
nearly vertical horn which is smooth and covered on its anterior 
surface with a thick mat of golden hairs; and the front legs, espe- 
cially the robust tibiae and tarsi, are monstrously elongate, with 
the last tarsomeres sporting thick growths of golden hair on their 
ventral surfaces. 
Howden and Campbell (1974) observed two struggles between 
males in nature at apparent feeding sites on long thin stalks of a 
bamboo-like plant. Wille (1943) also noted G. aegeon (especially 
males) on sugar cane stalks. This study is a follow-up of these 
observations to determine the functions of the males’ bizarre sec- 
ondary sexual structures. 
Methods 
Males were captured near lights at night and kept individually in 
metal canisters where they were provided with pieces of ripe banana 
or plantain which they appeared to eat. Fights were staged in the 
evening on nearly vertical, 1.5-2. 5 cm diameter stalks (mostly the 
central rachi of palm leaves from which I had stripped the leaflets). 
The first male was placed on the stalk facing down, and within 1-5 
min. the second was added below him, facing up. Super-8 movies 
made of eight fighting sequences and associated behavior were 
analyzed frame by frame. Substantial enlightenment was also 
* Manuscript received by the editor March 26, 1978. 
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