47 



humus and is no longer attractive. Young coconut stems rot, and are 

 infested, more quickly than old ones. 



In order to pupate, the larvae burrow about 12 inches into the 

 ground. When examining trap-heaps, especially if they are more 

 than 2 months old, the ground beneath them must also be examined. 

 Pupae were ^■ery seldom found in rotten stems, but in a few standing 

 ones newh'-emerged adults have been noticed, showing that the larvae 

 had been "unable to reach the ground. The inactive larval stage that 

 occurs prior to pupation averages about 1 1 days. 



The pupa is described. In the laboratory the average length of the 

 pupal stage was about 23 days. 



Many details about the adults are given. They emerge after an 

 inactive period of about 20 to 24 days. The males predominated 

 both in the crowns of dead or injured coconut palms and in trap- 

 heaps, where they represented 60-6 per cent, of the total. There is 

 no doubt that the beetles feed in the crowns of the palms, but mate 

 in the future breeding places of the larvae, though mating may also 

 occur in the crowns. The various forms of injury by the beetles are 

 illustrated. The holes made by them only prove fatal in cases where 

 water runs into them or the palm weevil {Rhynchophorus) is able to 

 enter. The injury done by the larger 0. tritubercitlatus does not differ 

 from that of 0. rhinoceros. Photographs show the different appearance 

 of palms killed by lightning and by rhinoceros beetles. In the former 

 case the outward leaves hang down, while serious injury by Oryctes 

 or Rhynchophorus causes the central leaves to fall first. In addition 

 to coconut, other palms that may be infested are : — -Corypha gebanga, 

 Livistona, Latania, Sabal, Metroxylon sagus, Pinanga, Nipa fructicans, 

 and oil palms. Agave sisalana is also attacked. The author agrees 

 with Banks that the beetles do not eat fibre, but feed on the sap only. 

 The principal time of flight is between 6 and 7 p.m., and the beetles 

 usually seek palms near their breeding places. The limit of distance 

 appears to be a few hundred yards from the edges of a coconut planta- 

 tion ; for complete security it may be fixed at about 1 kilometre. 

 In Samoa the adults and larvae are said to have been able to spread 

 to distances up to about 6 miles. In 1919 Oryctes was found in the 

 Strait of Sunda on the volcanic island of Krakatoa, on which all life 

 was destroyed by the eruption of 1883. The nearest island is 12 miles 

 away, and Java 24. As much drift-wood floats on the rapid current, 

 it is suggested that this spread is due to larvae or pupae transported 

 in coconut logs. Experiments showed that most of the larvae in a log 

 submerged in water with a salt content of 2-8 per cent, survived after 



24 hours. The Sunda current can carry a log across in 18 hours. 

 It is possible that in Samoa the larvae have been distributed in a 

 similar manner. 



In captivity the maximum life of the adults is 4-4J months. 

 Oviposition begins 20-62 days after emergence from the cocoon. 

 As many as 71 eggs have been obtained from a single female ; formerly 



25 was believed to be the normal number. 



On the West Coast of Sumatra all stages of development occur 

 throughout the year. In the eastern part of the Malay Archipelago, 

 where there is a long dry monsoon, some periodicity is probable. 



Recorded natural enemies include birds, pigs, a fungus [Metarrhizium) 

 and Scohid wasps. One of the last-named, Triscolia rubiginosa, 

 parasitises Xylotrupes gideon, L., in the Dutch East Indies, but though 

 it paralyses captive larvae of Oryctes, all attempts to rear its larvae 

 on those of Orvctes have failed. 



