1977] 
Eberhard — Behavior of Golofa porteri 
297 
cifics. This species is thus in accord with the tendency seen in other 
beetles for such male structures to function as weapons in intra- 
specific battles (Eberhard in press). It differs from the others in- 
vestigated so far in that the legs and horns (at least the prothoracic 
horn) may have the additional function of intimidating opponents 
with prefight visual displays; the fights occur at least sometimes 
during the day in the open, and the jerking movements of the front 
legs may serve to focus attention on them. 
The elongate front legs constitute the most unusual feature of 
this species, and it is possible to speculate on possible evolutionary 
sequences for their development. Head horns, functioning to pry 
up adversaries in what seems to be the usual beetle manner (see 
Eberhard in press) probably evolved first. The effective use of the 
head horn probably involved pushing ventrally with the front legs 
at the moment of dorsal flexion of the head to impart maximum 
dorsal thrust; it may have also involved clamping the opponent 
against a thoracic horn and lifting him away from the substrate. 
Two possible sequences leading to long legs occur to me. 1) Pre- 
liminary lengthening of the front legs might have been advantageous 
to permit the beetle to apply the downward thrust of the legs far- 
ther forward, thus giving greater mechanical advantage to the head’s 
upward thrust since the lift would be exerted nearer the beetle’s 
center of gravity. Both head horn and front legs might have then 
increased in parallel fashion since better purchase would increase 
the effectiveness of a longer horn as a pry. The next stage would 
begin when the front legs were long enough that they reached the 
opponent’s middle legs and occasionally dislodged one accidentally 
as they pushed down during a thrust. Natural selection could then 
favor further elongation of the legs, perfection of the timing and 
form of the ripping movement, and concomitant loss of the 
bracing function during head thrusts until the present state was 
achieved. 2) Lengthening of the front legs might have begun as 
an adaptation to raise the opponent farther from the substrate 
after he had been clamped between the head and prothoracic 
horns. Raising him farther would be advantageous because he 
would be more likely to lose his contact with the substrate, and 
would thus be more likely to fall free when dropped. Selection of 
this sort may have occurred in other beetles like Chiasognathus 
grandti, which have moderately long front legs and which lift op- 
ponents in fights in the open (Joseph 1928). When these long legs 
