Rhinoceros Beetles in West Africa — HOYT 
451 
DISCUSSION AND CONCLUSIONS 
In both Sierra Leone and western Nigeria 
predators and parasites or Oryctes larvae were 
not at all common. The only controlling factor 
of this nature seemed to be periodic invasions 
of the fallen logs by "driver” ants. Standing 
rotten palm trunks contained large numbers of 
Oryctes in all stages of development. It should 
not be supposed, however, that there were nor- 
mally large numbers of these breeding sites in 
any one small area. Further, not all of the trunks 
contained Oryctes. It was noted that rotten 
trunks with long black fibers in their interiors 
seldom supported anything at all. Perhaps the 
form of decay, fungal or bacterial, made these 
unattractive to the beetles. 
In areas like one reported in western Nigeria 
where an old oil palm plantation had been poi- 
soned off and the dead palms left standing, 
serious damage was caused to the young palms 
planted between them by Oryctes, which bred 
in the rotten trunks. 
Parasites and predators were found readily 
only in the regions of the deltas of the Niger 
and Cross rivers of eastern Nigeria. While the 
same species of these are wide-spread through- 
out West Africa, they were common in this 
particular area. It is thought that the practice 
of burning off the bush, which is done on a 
large scale in western Nigeria and Sierra Leone, 
plays an important role in limiting the numbers 
of predators and parasites. The land of the delta 
areas is too swampy for burning. Oryctes is not 
affected by bush fires on account of its habits. 
It is, of course, logical to assume that the 
long dry season, together with the absence of 
numerous streams and swamps, probably also 
plays a major role in limiting populations of 
parasites and predators which have fairly short 
life cycles. No doubt it does, but this and burn- 
ing complement each other, and it is difficult to 
say which is the more important. 
Under West African conditions it appears 
that many of the populations of Oryct ^-%. re 
limited by the number of available and suitable 
breeding sites, and that their predators and 
parasites are limited by unfavorable environ- 
mental conditions which are determined largely 
by cultural practices and climatic conditions. 
