Hi 



I'ROGHOPPRR r>LI(THT OK NI.GA R-CANK, 



Fig. 32. 



Fig. 32^Simple form of light tra]) foi' attracting adult fioghojipers. 



The method sufifers from the great disadvantage that practically all 

 the specimens caught are males. Gough (1910 A. p. 306) has given 

 coimts of over ten thousand individuals caught in light traps h>howing 

 about 1^ per cent, females. (11,257 males to 175 females). My own 

 records and those of other observers entirely confirm these results. In 

 many cases the propoition is even lower than this and as a result the 

 use of light traps is of comparatively little use as a control method. 



Intensity of Licjlit. Investigations have been made by different 

 workers on the relative attracting powers of different intensities of light. 



Urich with a Kitson kerosene-vapour lanjji uf 1,000 candle power 

 found that the increased attraction was sliglit and in some cases the 

 more powerful lamp attracted fewer froghop[)ers. In tliree evenings 

 the powerful lamp attracted 163 insects while one oil lamp attracted "241 

 individuals on the following three nights, while during August 1910 the 

 Kitson lamp attracted 7.447 froghoppers and three hurricane lamps 

 attracted 3,929, which is more in favour of the powei-ful light (Urich 

 1910 A. p. 20). 



In British Guiana J experimented with an acetylene lamp of about 

 100 candle power and caught 651 individuals (1*2 per cent, females) while 

 an oil lamp in the next bed caught 525 (1-2 per cent, females) of Totriasjm 

 flavilatera. 



