450 
region. Probably because of its size, the species 
has been confused with O. gigas of Madagascar. 
Oryctes owariensis breeds, as far as is known, 
only in rotten wood and prefers rotten palm 
logs. It was found commonly in Sierra Leone 
and Nigeria in standing rotten oil palm trunks, 
standing rotten coconut trunks, and in rotten 
Raphia palm trunks. Usually this was the only 
species of Oryctes present in these sites, but 
sometimes the larvae of O. monoceros or O. 
ohausi occurred with it. In Sierra Leone an adult 
specimen was extracted from the crown of an 
oil palm. Observations in both Sierra Leone and 
Nigeria seemed to indicate that this beetle did 
not prefer coconut palms as a host plant. 
4. Oryctes sjostedti Kolbe 
As has been stated previously, this species 
was only taken breeding in the debris accumu- 
lated in the dead leaf bases just below the 
crowns of oil palms. In this site the maximum 
number of larvae found was six, all third in- 
stars. Pupae were not infrequently encountered, 
usually in a cavity within one of the old leaf 
bases; the adult beetles were also found both 
within these and in the debris enclosed by them. 
Adults were taken at mercury vapour lights 
fairly 7 frequently, but never in numbers; one or 
two per night was the largest catch. This species 
was most common at Benin, Nigeria, on the 
West African Institute for Oil Palm Research 
station and at Umudike in eastern Nigeria. 
5. Oryctes ohausi Minck 
Perhaps this species has been confused with 
O. monoceros in the past; anyway when speci- 
mens were sent to the British Museum for de- 
termination, it was surprising to learn that no 
examples of this species were in the collection. 
0. ohausi was commonly found breeding in the 
standing rotten trunks of Raphia palms. Adults, 
larvae, and pupae were found in fair numbers 
in these sites, and not infrequently in company 
with O. owariensis. There was an average of 
eight larvae per trunk during April, I960, at 
Umudike in eastern Nigeria. A single adult 
male was taken in a rotten oil palm stump on 
Moor Plantation at Ibadan. 
PACIFIC SCIENCE, Vol. XVII, October 1963 
6. Oryctes erehus Burmeister 
This species has been recorded a number of 
times from West Africa but was not found 
during this investigation. 
NOTES CONCERNING ADULTS OF Oryctes 
All of the investigations conducted in West 
Africa on the adults of the various species of 
Oryctes were carried out with the objective of 
finding parasites of the mature beetles. 
The main difficulty in searching for parasites 
of the adults is to get large numbers of beetles 
which have been exposed in nature. When ma- 
ture beetles are taken from rotten logs, a fairly 
high proportion of them are recently emerged 
and have never been outside the breeding site. 
If Oryctes flew readily to lights, the problem 
would be simple. However, it is not particularly 
attracted by light, although recently some suc- 
cess has been reported with a special ultra-violet 
lamp used in the Pacific. 
In Western Samoa split logs laid flat on the 
ground are used to trap adult rhinoceros beetles. 
Each trap consists of four to eight logs each 
about 4 ft long. A similar type of trap was tried 
in Nigeria without success. 
Another type of rotten log trap was devised 
which gave fairly good results in Nigeria. This 
was made of a foot-tong section of coconut 
trunk through which a hole was bored from end 
to end. This section was placed on top of a 
No. 10 can which was either sunk into or rested 
on a coconut stump. The beetles landed on the 
top of the log, crawled down the hole and fell 
into the can underneath. The trap caught quite 
a few Oryctes monoceros , the largest single catch 
being three. 
Efforts were made to use captive beetles to 
attract others. No positive results were obtained 
along this line, but it was found that 0 . owari- 
ensis had two distinct flight times, one in the 
evening and the other in the early morning. 
Furthermore, beetles which did not fly in the 
evening flew in the morning, and beetles which 
did fly after sundown did not fly later on. 
No parasites were found in the adults of 
Oryctes, but the numbers examined were prob- 
ably not high enough to give any reasonable 
hope of success. 
