THE SUGAR-CANE LEAFHOPPER. a6 
cages sent to the plantations the cane cuttings and the cane itself were well sprayed 
with water containing spores of the fungous disease, so that these would be certainly 
carried abroad by the emerging hoppers and parasites. I imagine there is no doubt 
as to this disease becoming established in all suitable localities. 
In speaking of the necessity for the continued propagation and dis- 
tribution of the introduced parasites of the leafhopper, Doctor 
Perkins reports as follows: “ 
Owing to the manner in which cane is cultivated in these islands, the entomologist 
working along the lines that have been adopted to control the leaf-hopper pest, meets 
with a serious obstacle such as is not encountered in dealing with insects injurious to 
our other vegetation. I refer here to the universal custom of burning off the trash over 
great acreages, after the crop has been harvested. I have been told that on the Colo- 
nial Sugar Refining Company’s estates in Australia no such burning off is allowed. Ii 
this is correct, it may help to account for the insignificant numbers of our cane-leai 
hopper there, as well as of several other insects of the same group, which are fortunately 
not known in our cane fields. As, however, burning of trash is an established fact here, 
it becomes necessary to see what steps can be taken to provide against this serious disad- 
vantage. I will first show whereof this disadvantage consists. The parasitic enemies 
of the leaf-hopper are mostly delicate and minute creatures, not accustomed to take 
prolonged flights. Their wings serve well to bear them from plant to plant, but for fur- 
ther 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 parasite yet present will be destroyed, but the adult leaf-hoppers on 
the other hand are well able to take care of themselves. When, as an experiment, a 
patch of about nine acres of cane, so heavily 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-hoppers 
spread to new fields of very young cane, and with what regularity they distribute them- 
selves over the young plants. It cannot be hoped that the parasites will (except under 
rare and fortuitous circumstances, such as constant favorable winds) spread themselves 
in like manner, and in the same time. Yet it is essential that the parasites should be 
on the spot when the leaf-hopper begins to lay in order to secure proper control. Ii 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 possible enemies. When 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 and stocked as aforesaid, at the time 
the much younger cane of the rest of the field began to be infested with hoppers, would 

@ Perkins, R.C. L.—Leaf-hoppers and their natural enemies. <Hawaiian Sugar 
Planters’ Exp. Sta., Div. Ent., Bul. 1, introduction, pp. xvui-xx1, May, 1906. 
