fourth, if not one-half, of all the grass growing annually is de- 

 stroyed by leaf^ioppers. 



The calculations of Reaumur and Huxley regarding the 

 increase of parthenogenetic Aphidae are classic; Reaumur 

 thought that one Aphid might be the mother of 5,904,900,000 

 in one month, while Huxley supposed that the tenth brood 

 alone of a single Aphid — // ell the members survived — would con- 

 tain more: ponderable substance than 'half a million of stout 

 men. Buckton, however, shows that this is much underesti- 

 mated and calculates that at the expiration of 300 days, the 

 progeny of one Apliid (each Aphid producing 20 only) would 

 be the 15th. power of 210, which is the almost inconceivable 

 number of 17,000,000,000,000,000,000,000,000,000,000! and this, 

 I believe, is really considerably underestimated. 



In comparison with these stupendous figures, the generation 

 of the cane leaf-hopper sinks into insignificance, but taken by 

 itself is sufficiently serious. 



It is very difficult to base calculations on this extraordinarily 

 variable insect in respect of the number of eggs deposited, and 

 the length of time taken for their metamorphoses, but suppos- 

 ing each hopper to lay only 50 eggs, (the sexes to be about 

 equal) and there to 'be but 6 broods in the year, then the undis- 

 turbed progeny of one impregnated 'female would amount in 

 one year to very little less tlfan 500,000,000. 



As an offset to this, there are but few beneficial Hemiptera. 

 The predaceous Reduviidae often attack our friends and foes 

 indiscriminately, for example it seems a matter of indifference 

 t'.' Zeliis peregrinus whether it seizes the destructive Perkiiisuila 

 or the friendly Coceinella. Certain Coccidae exude merchantable 

 wax and others provide formerly important dyes, w'hile cer- 

 tain waterbugs furnish food for game and cage-birds or even 

 to some races of man, but the total value is insignificant. 



