SECTION X. — METHODS OF CONTROL. 147 



It will be seen that by this method adults, including about 30 per 

 cent, females, can be destroyed in large numbers, the chief drawback 

 being that the method is seldom successful before 5 p.m. and at the time 

 of the second brood it is usually dark before 7 p.m., so that work can 

 only be carried out for a limited time each day. 



To increase the rapidity of the work and reduce the labour required, 

 experiments have been continued with various forms of nets drawn by 

 mules, one of the most successful being one in which a miile walks 

 between two rows of canes and has attached on each side a net in the 

 form of a pannier which sweeps the rows of canes on either side. 



This will be tested more fully this season ; it is not expected to 

 be more than moderately successful but may be applicable to small and 

 localised outbreaks. 



An account of the net in its present form will be found in the 

 Bulletin of Entonaological Research Vol. XI p. 179. 



It was thought at one time that it might be possible to use the frog- 

 hoppers caught in the nets to infect with green muscardine and release, 

 but in view of the high proportion of females caught and the impossi- 

 bility of separating them from the males it is probably better to destroy 

 them than to use them in this way. 



A somewhat similar method has been suggested for use in Cuba by 

 Cardin 1917 but in this case it is the pastures that are attacked, and the 

 net or hopperdozer is mounted on skids which slide over the ground. 



ENCOURAGEMENT OF NATURAL ENEMIES. 



In the section dealing with the enemies of the froghopper the habits 

 of each of them has been discussed so far as is known. 



Some methods may be adopted by which they can be encouraged. 

 Thus birds may be attracted to estates if trees are left here and there in 

 the traces, or if necessary planted in areas where all have been destroj^eil. 



Keskadees and other birds are encouraged if posts are put up for 

 perches along the traces. On one occasion this was done and many of 

 the posts took root and grew into convenient bushes. 



The reduction of the amount of burning to the minimum will save 

 many lizards, frogs, toads, spiders, and other enemies that would other- 

 wise be destroyed. 



To increase the number of egg parasites Urich brought grass from 

 the moister parts of the island, where the vermilion parasite is 

 abundant, in to the cane fields, but no conclusive results have yet been 

 announced. 



It is unfortunate that several good agricultural processes are destruc- 

 tive to natural enemies. Thus better drainage reduces the numbers of 

 the frogs and toads, and the better cultivation of abandoned lamls 

 destroys the nesting places of many birds. At the same time it has 

 been shown that these processes have also their beneficial aspects and 

 they should be carried out in spite of any small possibly injurious effect. 



THE INTRODUCTION OF NEW ENEMIES. 



As the search for new enemies of the froghopper has been several 

 times suggested and an attempt made in this direction, a few notes on 

 this question will not be out of place. 



When a new pest is introduced into a country and, adapting itself to 

 its new surroundings, increases with great rapidity owing to the lack of 

 controlling factors, the introduction of enemies of the pest from it>i 

 original home to its new habitat is an obvious measure to be taken. 



