SECTION VI. — NATURAL ENEMIES OF THE FROOIIOPPER. Si^ 



TABLE VI. BALANCE SHEET. 

 Credit. 



?8 Rats. 



About GOO injurious insects. 



3 Crabs. 



Dekit. 



26 Birds. 



17 Lizards. 



29 Frogs and Toads. 



44 Useful insects. 



44 Spiders. 



The evidence incriminating the inonfroose is as follows : — 



(a) The froghopper blight in Trinidad has been apparently more 

 abundant in the last fifteen years, within the time that the mongoose 

 has been to any extent widespread in the island. 



{h) There is a general of)inion among all the older planters in the 

 colony that wild birds and lizards are much less common nowadays in 

 the cane districts than formerly, and as many of them eat froghoppers, 

 their reduction would allow the froghoppers to increase. 



(c) The mongoose is known to destroy lizards, frogs, toads and birds. 



{d} In most countries where the mongoose has been introduced it 

 has acquired a reputation for destroying birds and lizards and causing 

 outbreaks of insect pests. 



On the other side the following observations can be made. 



(a) Although outbreaks of blight have apparently been commoner 

 within the last fifteen years, we have accounts of blight of a similar 

 nature many years before the mongoose was introduced, and outbreaks 

 definitely known to be due to the froghopper so soon (1889) after the 

 introduction of the mongoose that its influence cannot have been 

 concerned. Further the outbreaks of blight even in the last twenty 

 years have not been correlated with the spread or numbers of the mongoose. 

 In 19U6 there were serious outbreaks in the Nuparimas. ;iltlioui;h the 

 mongoose was still mre in that district. 



(L) Many other causes during the past fift\- years have tended 

 towards a reduction of animal life in the cane fields. incLeased 

 population, spread of cultivation and destruction of forest areas. are noi 

 the least of these. Better drainage has reduced the number of breeding 

 places for toads and frogs, better cultivation and the reduction of abandoned 

 land destroy breeding places for birds and lizards, and last, but not least, 

 the practice of burning the canes before cutting and of burning the 

 trash after cutting, fortunately less frequent now than formerly, both 

 desti'oy a considerable proportion of the animal life in the cane fields. 



If it is held that injurious as well as useful animals and insects are 

 thus destroyed it must be pointed out that the injurious insects breed 

 more rapidly than birds, lizards and toads and hence recover more 

 quickly and cause damage before their slower breeding enemies have 

 again become efficient. • 



(c) Although, as shown by Table V and my previous report the 

 mongoose destroys birds, a large proportion of these are domestic fowls, 

 which do not concern the present enquiry, and of the others many are 

 not insect-eating. 



