146 FROGHOPPER BLIGHT OF SUGAR-CANE. 



Other Insects Destroyed. A number of experiments have been made 

 to find what other insects are destroyed by the use of light traps. The 

 list is a large one and includes both useful and injurious. Some of the 

 principal are as follows : — 



Useful. Neutral, Injurious, 



Mantidae ...Crickets ...Hard-back beetles. 



Candle-flies (Lampyridse)... Cockroaches. ..Mole-crickets. 

 Xiphidimn (grasshoppers)... Crane flies ...Small moth borer (Diatraea) 

 Soldier bugs (Eeduviidfe)... Beetles ...Leaf eating grasshoppers. 



Ichneumon flies ...Ants ...Termites. 



Use of Lamjs for spread of Green Muscardine Fungus. Owing 

 to the small proportion of females attracted light traps are of little use 

 as a direct control method. It has however frequently' been suggested 

 that they could be used in order to infect the adults with the green 

 muscardine fungus. 



Borer (1910 B. p. 478) first suggested the use of a trap round the 

 lamps and that the froghoppers so caught could be infected and released 

 the next day. Gough (1911 C. p. 38) suggested that if the spores were in 

 the trays round the lamps infection would take place without the 

 additional expense of a trap. 



Rorer's trap consisted of a zinc funnel beneath the lamp down which 

 the insects slipped into a box below. I have tested this and several 

 other types of traps, and while occasionally quite successful and one of 

 the best methods of distributing the fungus, it is uncertain and suffers 

 from the defects which are discussed more fully on p. 85. 



Use of Lamjis for indicating broods, A few light traps on an 

 estate put out about once a week, and in which the total captures are 

 counted, are of great value in determining the occurrence and dates of 

 the broods, and when the damage may be expected to increase and when 

 recovery maj' set in. 



The diagrams in figs. 5 and 6 show results obtained in this way. 



Use of Nets. In British Guiana in 1916 I found that the adult 

 froghoppers could be caught in large number- by sweeping the grass 

 and canes at the sides of the field drains during the daj with nets. In this 

 way boys could catch up to 8,000 adults per day instead of five or six 

 hundred by the old method of hand collecting (Williams 1918 B. p. 170). 



In Trinidad the same method was found to be useless owing to the 

 habit of the froghopper here of spending the day hidden away in the 

 axils of the upper cane leaves. 



It was not until two years later that it was observed that in the early 

 evening the adults leave this position, crawl out on the leaves of the 

 cane and are readily captured. 



On 9th July 1918 (1st brood) at about 6 p.m. I captured 700 adults in 

 about two minutes with an ordinary butterfly net on a trace between 

 infested cane fields. About 81 per cent, of these were females. 



The same results can be obtained in the early morning and on the 

 followmg day at about 6 a.m. I obtained 122 adults (including 29 per 

 cent, females) in one minute by the same method. 



At six p.m. on the following evening 1,210 adults were captured in 

 five minutes with the same net, and two days later with a lax'ger net, 

 6 feet wide by 2 feet high, drawn by two men 3,000 froghoppers were 

 obtained in two minutes. 



