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PACIFIC SCIENCE, Vol. XVII, October 1963 
Nigeria. They were never common, and in Sierra 
Leone only 24 were collected from over 500 
rotten oil palm trunks. Specimens were de- 
termined at the British Museum to be perhaps 
a species of Alaus. 
A smaller elaterid larva found in a rotten 
oil palm was reared on Oryctes and cetonid 
larvae, the adult beetle being identified as Calais 
sp. 
2. Occasionally larvae and adults of a small 
carabid beetle, Morio guineensis, were found in 
the frass in the rotten palm trunks. In the 
laboratory these readily consumed first instar 
Oryctes larvae. 
3. Large numbers of the larvae of Oryctes 
boas F., collected from a manure heap on the 
farm of the University College, Ibadan, were 
reared in captivity. These were dissected when- 
ever they showed signs that something was 
wrong with them. One, a prepupal stage larva, 
died suddenly and was cut open. In the abdomen 
was a very large larva of a tachinid fly which 
had also perished. Following this discovery, some 
1,000 Oryctes boas grubs were collected from 
this manure heap, but no other parasites were 
recovered. 
4. Neanides and adults of the large reduviid, 
Platymerus biguttata, were found fairly fre- 
quently in the open hollow tops of the standing 
rotten oil palm trunks in Sierra Leone during 
April, May, and June. Laboratory trials were 
conducted to see if this bug would prey on adult 
Oryctes owariensis, but without result. Even 
adults which had been held without food for 
nearly 2 weeks showed no interest in this large 
rhinoceros beetle. During May and June, 1959, 
Platymerus biguttata came to lights at night on 
several occasions. No other Coleoptera than 
Oryctes owariensis were tried as prey for this 
reduviid. 2 
5. In a standing rotten coconut palm trunk 
on Moor Plantation, Ibadan, three tabanid larvae 
2 The author is at present engaged in a study of the 
allied species, Platymerus rhadamanthus Gerst., which 
does attack the adults of Oryctes monoceros Ol. How- 
ever, old adults which have accumulated large fat 
deposits usually refuse to attack anything. At the 
time Platymerus biguttata was investigated it was not 
known that the fifth-instar neanides would also at- 
tack adult rhinoceros beetles and, perhaps because of 
their more rapid metabolism, are generally easier 
subjects with which to work. 
were found in the frass along with the grubs 
of Oryctes monoceros. These readily attacked 
and killed young scarabaeid larvae in captivity. 
A week or so later all three pupated and after 
2 weeks the adult flies emerged. Unfortunately, 
the specimens sent to the British Museum were 
badly broken in transit and were not able to be 
identified. The tabanids were bright orange with 
a large purple band across each wing. 
6. In Sierra Leone, both inside the hollow 
tops of standing rotten oil palm trunks and in 
the crowns of living oil palms, a large aviculariid 
spider was frequently encountered. This fear- 
some-looking arachnid evidently attacked the 
oil palm climbers, who had their own remedy 
for the effects of its bite. Experiments were 
made to see if this spider would kill adult 
Oryctes owariensis, but the results were negative. 
In Nigeria this palm tarantula seemed to be 
unknown to the people and no specimens were 
found. 
Coleolaelaps sp. (Acarina, Laelaptidae) 
Several investigators have reported that mites 
feed on the eggs of Oryctes. Venkatraman re- 
ported a Coleolaelaps sp. which "apparently fed 
on Oryctes eggs” in Ceylon. Surany reported 
several instances of mites feeding on Oryctes 
eggs and stated that they were important under 
certain circumstances in its control. Unfortu- 
nately, Surany did not identify the mite in 
question in his report. 3 
Clusters of mites around eggs of Oryctes 
owariensis were frequently observed in Sierra 
Leone from June onward throughout the rainy 
season in 1959. These mites were found on eggs 
enclosed in balls of frass formed by the adult 
beetles as they oviposited in the rotten wood 
inside the standing rotten oil palm trunks. It was 
noted at the time that eggs which had mites on 
them never hatched, while eggs in the vicinity 
without mites hatched readily. These mites were 
collected and sent to the British Museum where 
they were identified as Coleolaelaps sp. 
Adult mites of this species were common on 
the larvae of Oryctes owariensis , O. boas, and 
O. monoceros, but were encountered only rarely 
on the adult beetles. 
3 Diseases and Biological Control in Rhinoceros 
Beetles. South Pacif. Com. Tech. Pap. 128. I960. 
