A FROGHOPPER ON SUGAR-CANE IN BRITISH GUIANA. 171 



for two reasons : (1) it allowed a current of air to pass through the net when in use, 

 so that insects were not blown away from the net by the draught created ; (2) it 

 allowed the escape of the small parasites which would be swept up by the net. The 

 edges of the outer bag were always allowed to project for the two inches beyond the 

 mosquito net in order to protect it from wear and tear. The inner and outer bag 

 could be cut from one piece of canvas as shown in the second figure. The part of 

 the net which passes round the ring is best reinforced with stout webbing. Even 

 the strongest net bag was usually worn out after one or two week's continual use. 



The boys walked down the drains through the cane-fields sweeping the grass on 

 either hand. About every twenty minutes (usually at the end of a drain) the net 

 was squeezed in the hand to incapacitate the contained insects, which were then 

 removed (by putting the hand through the central funnel bag) and transferred to a 

 tin box. In this way boys were able to catch 3,000-4,000 adult froghoppers in a 

 very short working day of not more than 5 hours. The largest number actually 

 brought in when I was there was 3,600 ; but supervised sweeping on one drain, 

 which had already been swept about two hours previously, produced 500 hoppers 

 in 20 minutes, so that an average of 1,000 an hour ought easily to be reached. 



The boys were offered two cents (Id.) per hundred. During September 1916 

 at Plantation Ogle two to ten boys collected on twenty-two days and caught 533,540 

 adults. During the same period 540,000 nymphs were hand-picked, but this required 

 a larger gang, and a higher price (4 to 5 cents per himdred) had to be paid. During 

 the year 1916 over 4,000,000 adults and nymphs were destroyed at Plantation Ogle 

 on an infested area of about 30 acres. 



Several hundred specimens from the sweep-nets were taken at random and the sex 

 determined ; as a result 46 per cent, were found to be females. 



Two light traps were tested in comparison, one an oil lamp and one an acetylene 

 light. The former caught 525 and the latter 651 froghoppers in one night. Five 

 hundred of each of these were sexed and gave in each case 494 males and 6 females, 

 or 1"2 per cent, of females. It will also be noticed that the bright light is but very 

 little better than the oil lamp. These results agree absolutely with experiments 

 made in Trinidad. 



It will be seen that the method of sweeping is far more efficacious than the use 

 of light traps.* 



General Conclusions and Summary. 



At the time of my visit (1916) the froghopper could not be considered as a very 

 serious pest of sugar-cane. It was in some spots extremely abundant in the fields, 

 but by far the larger number were feeding on the grass. Even at its worst the numbers 

 nowhere approached those f oimd in Trinidad during an attack, and the canes suffered 

 very little visible damage. It would, however, be very difficult to distinguish the 

 present conditions in British Guiana from those that must have prevailed in Trinidad 

 before the insect became a regular pest. In view of this, the froghopper should 

 always be regarded as a possible great danger in Demerara, and any reasonable 

 precautions and preventive measures should be taken. 



* This remark applies only to British. Guiana. In Trinidad, owing to slight differences 

 in habit of the insect and in cultivation, the sweep-nets are quite useless. 



(C47S) f 



