THE PESTS AND DISEASES OF THE CANE 143 



The causes of the epidemics are obscure ; in some cases local conditions, 

 such as floods, may have caused them to desert their usual feeding places. 



Minor LepidopLrons Pests. — Of the lesser lepidopterous pests may be 

 mentioned various " bud worms," or the larvae of Tineid moths belonging 

 to the microlepidoptera, and mostly included in the genera Ereunetis and 

 Opogona. Normally these lai-vae feed on the dried leaf sheaths, but they also 

 penetrate and destroy the e5-e of the cane. They are of very wide distri- 

 bution. Another minor pest is the " leaf roller," Omoides accspta, which 

 does a certain amount of damage in the Hawaiian Islands. The life history 

 of both of these classes has been worked out by Swezey.^' 



Coleopterous Pests. — The coleoptera are equally destructive with the 

 lepidoptera, but with one notable exception their method of attack is 

 different. Nearly all the coleoptera which have been observed as cane 

 pests pass their larval stage underground as root eaters. They are popu- 

 larly kno^vn as grubs. The chief species of the root borers that have been 

 studied are : — 



Apogonia destructor}^ the Wawalan beetle of Java, illustrated in Plate 

 XVI, Nos. 5, 6, 7. 



Many species of Lachnosterna (May beetles), Diaprepes, Prepodes, and 

 Ligyrus ^^ (hardbacks) in the West Indies. 



Lepidiota alhohirta^^ (cane grub or grey back beetle) in AustraUa. 



Anomala sp.^^ in Hawaii. 



Phytalus smithi^^ in Mauritius. 



Of these species, Anomala, Apogonia, Phytalus, and Ligyrus are lamelh- 

 corn beetles, Lachnosterna and Lepidiota are scarabids, and Diaprepes is 

 a curculionid or snout beetle^ 



The damage done by these insects is very great, but, as the destruction 

 is not so patent, they have not become so notorious as have the lepidopterous 

 pests. Of all of them, that which causes most harm seems to be Lepidiota 

 albohirta in Australia, which, in spite of the efforts of skilful entomologists, 

 still remains an imperfectly controlled pest, sometimes causing the aban- 

 donment of otherwise suita,ble areas. 



The life history ol a West Indian root borer, Diapr^^pes abbreviatus, 

 is thus given by Watson. ^^ 



" In August and September the perfect insect lays its eggs on the upper surface 

 of the leaves, and after 10 days the grub emerges and falls on to ground, immediately 

 burrowing into the ground in search of food. The grub remains in the soil for 312 

 days, eating the root of cane, sweet potato, etc., and then pupates, the perfect 

 insect emerging in fifteen days to repeat the same cycle. The grub at first is 

 only I /i8th inch long, reaching at maturity a length of one inch." 



The most dangerous coleopterous pest other than the root borers is the 

 Hawaiian weevil borer, Rhabdocnemis obscurus. This insect occurs as a 

 pest all over the Australasian region. It is illustrated together with a piece 

 of dahiaged cane in Plate XVI, Nos. S and 9. The life history as given by 

 Koebele^* follows : — 



" The female beetle is easily separated from the male by its longer, smoother 

 and more slender beak, and its pointed terminal segment. She lays her eggs 

 consecutively, probably 4 to 8 each day, but less than this toward the end of the 

 period ol eight months during which she continues to lay. When the egg is laid 

 in the cane from the outside this is done from under the sheath, which the beetle 



