Investigations of Rhinoceros Beetles in West Africa 1 
Charles P. Hoyt 2 
In April, 1959, the author was sent by the 
South Pacific Commission to the countries of 
Sierra Leone and Nigeria, West Africa, to con- 
duct an investigation of the natural enemies of 
the various species of Oryctes (Coleoptera, 
Scarabaeidae, Dynastinae) occurring there. The 
object of this study was to find and introduce 
to the islands of the South Pacific suitable para- 
sites and predators of these beetles in order to 
establish a biological control over the introduced 
Oryctes rhinoceros Linn, which has become a 
serious pest of coconut palms in the area. 
In Sierra Leone and Nigeria, coconut palms 
are confined mostly to village sites; the groves 
are from 15 to 50 palms, depending on the size 
of the village. Because of this, nearly all the 
work was carried out on oil palms ( Elaeis gui- 
neensis Jacq. ) which, together with the Raphia 
palms of the swamps, are the most important 
hosts of the species of Oryctes found. The oil 
palms occur in an extensive belt that follows the 
coast of West Africa and extends inland nearly 
100 miles in some places. 
There are two distinct climatic seasons in 
West Africa, and these greatly affect the insect 
populations. The wet season begins generally 
at the end of April and lasts until sometime in 
September. By the end of November the dry 
season has set in, and from then until April 
little or no rain falls. At times the rains will 
cease in August and commence again in Sep- 
tember, but during I960 this type of rainfall 
did not occur in Nigeria. 
Insect activity begins with the coming of the 
rains in April or May and gradually ends in 
November or December. There are, of course, 
many exceptions to this; some species seem to 
be found only during the dry season and others 
congregate along streams and in swamps, giving 
a false impression of their absence. 
1 Presented at the Tenth Pacific Science Congress, 
Honolulu, Hawaii, 1961. 
2 Technical Officer, Pe$ts & Diseases, South Pacific 
Commission, Noumea, New Caledonia. 
Manuscript received March 19, 1962. 
During the dry season in Sierra Leone and in 
parts of Nigeria, it is the practice to burn off 
the bush to clear the land for planting. The oil 
palms in these areas are usually not affected by 
the fires, and the larvae of Oryctes and other 
beetles within the standing rotten trunks are 
not harmed. 
The low-lying land of the southern part of 
eastern Nigeria is divided by numerous slow- 
moving streams which give rise to large swampy 
areas as they wind their way towards the sea. 
Because of this and the heavy rainfall, extensive 
burning is not possible. In the swamps are dense 
stands of Raphia palms which flower and die, 
providing a continuous supply of breeding sites 
for Oryctes. The higher ground between the 
streams and swamps supports large stands of oil 
palms, both cultivated and wild, from which 
come the main export of the area in the form 
of palm oil and kernels. 
PREDATORS AND PARASITES ENCOUNTERED 
Neochryopus savagei Hope (Coleoptera, Cara- 
boidea, Scaritidae) 
The large scaritid beetle Neochryopus savagei 
was first found in Raphia palms growing in the 
swamps at Umudike, near Umuahia, eastern 
Nigeria. In April, I960, an adult beetle of this 
species was found inside a standing rotten 
Raphia palm trunk where it was actually en- 
gaged in feeding on a larva of Oryctes ohausi 
Minck. A search of other rotten palm trunks in 
this area turned up two large larvae of Neo- 
chryopus. Afterwards, additional adult speci- 
mens were recovered from the debris which 
normally collects in the old dead leaf bases just 
below the crowns of oil palms left by workers 
engaged in cutting the bunches of fruit in a 
grove of palms on the Agricultural Station. This 
accumulation of rotten organic matter provides 
a breeding site for Oryctes sjostedti Koble, and 
Neochryopus breeds here and preys on these 
dynastid grubs. 
444 
