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Smyth (E. G.). The White Grubs injuring Sugar Cane in Porto Rico. 

 II. The Rhinoceros Beetles. — //. Dept. Apric. Porto Rico, San 

 Juan, P.R., iv, no. 2, April 1920, pp. 3-29, 4 plates. TReceived 

 1st October 1921.] 



This paper is the third of a series [cf. R.A.E., A, v, 410, 558]. 



The larvae of Stratcgus titaniis feed on organic matter in the soil. 

 Such damage as severing underground stalks is accidental, and attacks 

 are only serious if the beetle is abundant and the sugar-cane is suffering 

 from drought and inadequate manuring. The adults cause no direct 

 injury and only occasionally bore into the base of the stool for 

 oviposition. It is difficult to determine the injury this beetle causes to 

 crops, as Lachnosierna {Phyllophaga) and Diaprepes, which are less likely 

 to be observed on examination, are almost always present with it. 



It is abundant in the humid districts of Porto Rico. Decaying 

 forest trees and stumps are its natural habitat, but as the result of 

 timber clearing, it has become a sugar-cane pest. The eggs are laid 

 singly in torn fibre or inside cane stalks. The average length of the 

 egg stage is 17i da\^s, and that of the larval stage 10 months. The 

 larvae usually attack rotted stems, and living ones are only infested 

 if the pest is abundant. In the prepupal stage they are especialh' sus- 

 ceptible to the attacks of fun.gi. The pupal stage averages 24 days. 

 Natural enemies include the mongoose, the Porto Rican blackbird 

 {Holoqtdscalus hrachypterus), and various species of mites, of which one 

 infests the adults and another destroys the eggs. A bacterium 

 {Micrococcus nigrofaciens) is often fatal to the larvae, and the green 

 muscardine fungus [Metarrhizium anisopliae) virulently attacks all 

 stages, of which the pupal is the most, and the egg the least, susceptible. 



Remedial measures recommended are the ploughing up of old canes 

 and the destruction of any larvae. Excess of organic fertilisation 

 should be avoided in fields subject to attack, and dead cane stubble 

 and dry stalks should be burned after ploughing. A poison bait 

 consisting of 2 lb. white arsenic (arsenic trioxide) or Paris green, 

 or 4-5 lb. lead, calcium or zinc arsenates mixed into 100 lb. of manure 

 or bagasse, which may be distributed round newly planted cane or 

 spread broadcast before the final ploughing, kills many larvae and 

 affords protection against hard-backs [Lachnosterna]. Manure heaps 

 placed at intervals along cane-field borders may serve as traps, 

 provided that they are regularly examined and the beetles found in 

 them destroyed. 



Strategus quadrifoveatus , P. de B., is only a minor sugar-cane pest, 

 but causes more damage to coconut plantations. The average life- 

 cycle lasts 14 months. The larva feeds on decayed wood and coconut 

 fibre round the base of old stumps. The adult feeds on the succulent 

 tissues of woody plants and trees and bores into coconut palms from 

 the level of the ground, thus differing from Oryctes rhinoceros, which 

 enters the stem high up among the leaves. 



The natural enemies are the same as those of 5. titanus. A mite, 

 Tyroglyphus heteromor pints, has been found on larvae collected in 

 rotten palm trees. Young coconut palms should be protected against 

 attack by treating the nuts and husks before planting with strong 

 repellents such as carbolineum or crude petroleum. The beetles 

 should be caught and killed when flying at dusk in the groves. Such 

 breeding places as decayed logs and stumps should be burned, but 

 if accumulated into piles will form traps, provided that they are 



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