﻿XIX 



which are fortunately not known in our cane fields. As, how- 

 ever, burning of trash is an established fact here, it becomes 

 necessary to" see what steps can be taken to provide against 

 this serious disadvantage. I will first show whereof this dis- 

 advantage consists. The parasitic enemies of the leaf-hopper 

 are mostly delicate and minute creatures, not accustomed to take 

 prolonged fiights. Their wings serve well to bear them from 

 l-)lant to plant, but for further distribution they are dependent 

 on air-currents. If when a field of cane is cut the wind blows 

 towards another cane field, no doubt some or many parasites 

 will reach it, but if otherwise, probably none will do so. In 

 burning over a field it is quite certain that almost every para- 

 site vet present will be destroyed, Init the adult leaf-hoppers on 

 tlie other hand are well able to take care of themselves. When 

 as an experiment, a patch of about nine acres of cane, so heav- 

 ily attacked by leaf-hopper as to be useless, was set on fire all 

 around to destroy these, it was noticed that the adult hoppers 

 rose from the cane in a cloud and spread to other fields ; so 

 this plan for destroying them was of no value. I have in an 

 earlier publication shown how quickly the leaf-ho]:>pers spread 

 to new fields of very young cane, and with what regularity they 

 distribute themselves over tlic young plants. It cannot be 

 hoped that the parasites will (except under rare and fortuitous 

 circumstances, such as constant favorable winds) spread them- 

 selves in like manner, and in the same time. Yet it is essen- 

 tial that the parasites should be on the spot when the leaf- 

 hopper begins to lay in order to secure proper control. If the 

 supply of laying hoppers at the beginning of the great breeding 

 season is very small, it means that there is not time for the 

 attack to become serious before that season is over. It is when 

 the hopper is least abundant, that one wants to be assured that 

 it is being attacked by all ]-)OSsiblc enemies. A\nien a field is 

 already seriously injured and swarming with hoppers, not much 

 immediate help can be given for obvious reasons. It will be 

 easier to prevent such a condition than to find a remedy. If 

 one could provide that in each large area of cleared land, ready 

 for planting, there should be in the middle a small patch of 

 some variety of cane most susceptible to the attack of leaf- 

 hoppers, that this cane should be kept well stocked with these, 

 and with a variety of parasites and predaceous insects, and 

 itself be of sufficient growth to afford good shelter to all these, 

 the condition from an entomological standpoint would be ideal. 

 This patch of cane, being already of suitable age and growth 



