April 1, 1920 Banana Root Borer 45 



From a few experiments the egg period was found to last from 5 

 to 7 days. From the character of the channels of the grubs it is the 

 opinion of the writer that the eggs are deposited in the outer sheaths 

 or between the outer sheath and the stem, the grubs working their 

 way into the body of the bulb or trunk. The work of the larva is 

 particularly destructive, since they girdle the plant in the immediate 

 vicinity of the lateral roots put out from the bulb of the plant (PL 11, A), 

 thus cutting off the passage of the sap. The larvae not only work fre- 

 quently in this region just described but may be found tunneling into 

 the main trunk as far as the heartwood. The larvae usually work below 

 ground, but in a number of instances the writer has found them in the 

 trunk as high as 2 feet above ground. The larval stage was found to 

 last over a period of from 15 to 20 days. Due to the scarcity of material 

 and to the fact that all infestations were gradually destroyed and cleaned 

 up, the writer was unable to make further records on the seasonal habits 

 of the species. 



The larvae upon attaining maturity construct an oval space at the 

 end of the burrows, usually vv^ell toward the outer layers, where the 

 larval head is cast, and where the lar\-a pupates. The pupae are naked. 

 Jepson found in Fiji that a period of from 5 to 8 days from the time of 

 pupation elapses before the emergence of the adult. The adults bear 

 wings and are very sluggish. When disturbed they Avill "play 'possum" 

 for a considerable length of time. The adults are gregarious and w^ere 

 found in clusters in cavities and depressions in the outer sheaths of the 

 banana close to the surface of the ground and also below the surface. 

 The length of life of the adult is not known. The writer has kept them 

 in captivity without food for two months. Jepson in Fiji has kept the 

 beetles in captivity about 14 weeks without food, and in the state of 

 nature they undoubtedly will live longer. In all probability the banana 

 root-borer continues to breed all the year round, provided that the food 

 supply is plentiful. The beetles are nocturnal, only coming up from the 

 soil at night for their activities above ground. 



CONTROL 



Since bananas are grovv^n year after year on the same land and are pro- 

 duced from suckers springing from the parent plant, a plantation usually 

 forms a breeding ground and nursery for these insects. The borer's mode 

 of life renders it a difficult pest to control, as Knowles and Jepson (10) 

 noted in Fiji. The egg, larval, and pupal periods are passed in or on 

 the bulb of the banana or plantain. The adults apparently do not move 

 far from the place where they have lived and developed so long as suitable 

 food is available to attract the egg-laying females. In Java Cosmopolites 

 sordidus is preyed upon and kept down by the larvae of a histerid beetle and 

 by those of some beetle of the family of Hydrophilidae. Jepson intro- 

 duced these species into Fiji, where the banana root-borer is a serious 



