444 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 7 



A NEW PEST OF CANE IN FIJI (SPHENOPHORUS 

 NEBULOSUS MACLEAY) 



By J. F. Illingworth, Ph.D., Professor of Entomology, College of Hawaii, Honolulu, 



T. H. 



This is a small beetle borer, similar in form to the ordinary cane 

 borer (Rhabdocnemis obscurus) . Though of smaller size it is exceedingly 

 prolific; fortunately, for the present at least, it appears to do little 

 damage to the sound cane. The}^ deposit their eggs in any rupture in 

 the stalk, hence they are very abundant in rat-eaten cane, or old stalks 

 which are full of exit holes of the ordinary borer. 



This beetle would prove a difficult pest to control if it ever became 

 abundant enough so that it was compelled to attack sound cane. ' Its 

 power of multiplication appears to greatlj^ exceed that of the ordinary 

 borer beetle. This fact was brought out during the breeding work of 

 the Tachinid parasites, when the ordinary beetle borers were bred in 

 large iron tanks, to obtain grubs for the flies. These tanks were filled 

 with short cane stalks, and about two or three thousand of the adult 

 beetles placed in each. Though we Avere careful to pick out all of the 

 beetles of this smaller species, sometimes a few found their way in with 

 the others. In such cases the smaller beetles produced so many eggs, 

 in the souring cane, that their larvae ate up most of the food from the 

 larger species. In place of finding only one or two here and there in 

 the stalk, as we do in the case of the larger grubs, these small larvae 

 were in dozens in each internode. They work along in parallel chan- 

 nels, side by side, and, unhke the large borers, never make rupture 

 holes through the rind for air. Hence a parasitic fly, such as we have 

 for the ordinary species, would have no chance to reach them. 



It must be recognized that though the larger beetles were more than 

 100 to 1 of the smaller in the breeding tanks, referred to above, the 

 conditions were not so favorable for their development. The larger 

 species prefer fresh cane, though their grubs will continue to live in 

 the stalks after they have become sour. A brief description of the 

 several stages may help to recognize this new pest. 



Larv^. Numerous in parallel channels of injured or souring 

 stalks; spindle-shaped, tapering gradually from about the middle 

 towards the head and tail. Comparing them with the ordinary borer 

 grub, the head is smaller in proportion; they lack the ventral enlarge- 

 ment of the fifth and sixth abdominal segments, and they usually 

 remain straighter. 



Pup^. In cavities just within the rind of the stalk; without cocoon. 

 This, and their small size will easily distinguish them from the ordinary 

 borer. 



