515 



sugar plantations. It is suggested that skunks and toads, which 

 eat large numbers of them and of the adult May-beetles, should be 

 introduced from the mainland. The hard-back beetle, Dyscinetus 

 trachyjyygus, Burm., was reported as greatly injuring sugar-cane on 

 the north coast. This Dynastid is very common in Porto Rico, the 

 larvae feeding upon decaying ratoons of sugar-cane and other grasses 

 and upon organic matter in the soil, but not apparently attacking 

 healthy roots. The life-histories of this and other species have been 

 worked out [see this Review, Ser. A, iv, p. 356]. The beetles were found 

 in great numbers feeding on the roots and underground stems of the 

 young cane, causing it to turn yellow and in some cases to die. They 

 had probably bred in grass lands in the vicinity or in the decaying 

 stools of the previous crop in the same field. Their presence constitutes 

 one objection to the practice of not burning cane-trash after cutting 

 the cane. It is suggested that trap- lanterns, placed over pans of water 

 and kerosene, should be used during the flight of the beetles, and 

 that night collections with lanterns should be made. A poison-bait 

 consisting of lib. white arsenic or Paris green and two quarts of cheap 

 molasses, mixed with a bushel of bran or lucerne meal and water 

 to moisten it, might be effective if scattered around the infested canes 

 after sundown. 



An important discovery during the year was that of a species of 

 Tetranychus (red-spider) attacking the foliage of sugar-cane. It was 

 first noticed on cane growing in pots in the latter part of April 1918, 

 on both surfaces of the leaf, forming a light webbing over the surface 

 and causing a mottled appearance of the leaves. The same pest was 

 observed in rearing cages on the south side of the Island four years 

 ago, but was not identified. The only previous report of a red-spider 

 attacking sugar-cane seems to be of T. exsiccator, Zehnt., occurring 

 in Java, but this is obviously a different species, being red in colour 

 while the Porto Rican species is a yellowish white. There is a possi- 

 bility of severe injury to cane by this species during periods of unusually 

 high temperature. 



A severe outbreak of Siphaflava (yellow cane aphis) occurred during 

 March and April on young seed- cane. These outbreaks are not 

 uncommon and are generally controlled by natural enemies before 

 severe injury results. Similar attacks have been recorded on older 

 cane but do not seem to cause the death of the plants. Experiments 

 showed spraying with contact insecticides to be unnecessary as in 

 untreated plots natural enemies proved equally efiicacious. 



Strategus quadrifoveatus, Beauv. (larger rhinoceros beetle) has been 

 recorded as causing severe injury to young coconuts and to mature 

 sugar-cane, some palms being killed by their attacks. It is proposed 

 to carry out experiments to determine suitable methods of controlling 

 the beetle ; in the meantime the following remedies are suggested 

 for trial. The coconut in the husk might be dipped, before planting, 

 into a repellent Hquid such as tar-oil or carbolineum, which retains 

 its odour for a long time. It is believed that it is the rotting wood 

 that attracts the beetles to oviposit and on which the larvae feed. 

 Another method, used with success in Samoa, is to collect the rubbish, 

 dead logs and stumps into piles in the coconut plantations. These 

 attract the ovipositing beetles and should be examined monthly 

 and all grubs and beetles in them destroyed. 



