Rhinoceros Beetles in West Africa- — Hoyt 
447 
trunk by the workings of xylocopid bees, a 
natural feature of all of the rotten logs in the 
grove. The ants entered through these holes, 
removed the frass, and ate the Oryctes larvae, 
leaving only the head capsules. 
5. 11 January I960 . The logs which had been 
invaded by the "driver” ants on the night of the 
10th were broken up to determine if any of 
the Oryctes larvae had escaped. In three of the 
logs in the upper breeding site experimental 
area a few intact larvae and pupae were found, 
but in the log located in the stream bed nothing 
remained. The following results were obtained 
from the logs in the upper area: One log which 
had been stocked with 7 larvae contained 1 liv- 
ing larva and 1 pupa; one log which had been 
stocked with 10 larvae contained 2 living larvae 
and 1 pupa; one log with no access from either 
end which had been stocked with 6 larvae con- 
tained 1 living larva and 1 pupa. 
The area was visited daily and the logs were 
inspected at intervals of 4 to 5 days to determine 
if the larvae were alive. The last stocking of the 
logs with larvae was on 16 December 1959. 
In November, the end of the wet season in 
Nigeria, the ants were active throughout the 
area. However, after the end of the rains the 
ants moved into stream beds; by January, only 
invasions of short duration were made into 
nearby areas. 
The invasion of the experimental site on 30 
November lasted about 14 hr. The last sortie 
on 10 January was only about 7 hr long. 
Another species of Dorylus ( Anomma ) was 
found in the coconut grove; this ant was never 
observed to enter the logs. No attempts were 
made by either species of Dorylus ( Anomma ) 
to enter the tops of the stumps or to climb up 
the standing trunks. The ants were able to climb 
vertical surfaces but did not seem to do any 
work, such as removing frass, while on them. 
When D. nigricans entered the rotten logs, they 
did so by choosing holes which were more or 
less horizontal. They always used these holes 
to bring out the frass from the interior. 
Ochryopus gigas Schio. (Coleoptera, Caraboidea, 
Scaritidae) 
Occasionally the very large scaritid Ochryopus 
gigas was found both in the debris accumulated 
below the crowns of oil palms and in standing 
rotten palm trunks. During April and May, 
I960, adults of this species were taken around 
lights at night. However, this species was never 
found to be common and its larva was not dis- 
covered. In the laboratory O. gigas attacked, 
killed, and consumed both larvae and adults of 
Oryctes. 
Scolia sp. ( Hymenoptera, Scoliidae) 
In the oil palm debris and in rotten Raphia 
trunks large Scolia cocoons were frequently 
found. Many of those taken from these sites had 
already hatched. Sometimes the head capsule of 
the host grub would be found entangled in the 
silk of the cocoon, and from this it was de- 
termined to be parasitic on Oryctes ohausi and 
O. sjostedti. 
The adult wasps were never observed in the 
field, but two males and two females were bred 
out in the laboratory. The female specimens 
were sent to the British Museum (Natural His- 
tory), where they were identified only as Scolia 
sp., "not in British Museum collection.” 
Judging from the number of empty cocoons, 
this parasite was thought to be rather common, 
but large-scale collecting efforts resulted in only 
about 65, nearly half of which contained dead 
pupae. Nevertheless, the cocoons were sent to 
Fiji where an attempt was made to rear the 
wasps. Unfortunately, this has proved unsuccess- 
ful, and the wasps which did hatch died in the 
laboratory. 
OTHER PREDATORS AND PARASITES 
1. Alaus ? sp., Calais sp. (Coleoptera, Ela- 
teridae) 
2. Morio guineensis Imh. (Coleoptera, 
Caraboidea, Carabidae) 
3. Genus ?, species ? (Diptera, Tachinidae) 
4. Platymerus higuttata Stal (Hemiptera, 
Reduviidae ) 
5. Genus? species? (Diptera, Tabanidae) 
6. Genus? species? (Araneida, Aviculari- 
idae) 
1. Large elaterid larvae were found inside the 
standing rotten oil palm trunks in close proxim- 
ity to Oryctes larvae in both Sierra Leone and 
