238 APPENDIX. [No. XV.B. 



tulips, in some cases even bo as to render ttem loathsome to the eye ratter 

 than an ornament. 



I have just received from Mr. Walker, the distinguished entomologist, 

 who is writing a work upon Aphides, a note, wherein he states that the 

 eggs of the vastator, together with the larvae, are abundant in his garden 

 under the strawberry leaves, and he has kindly furnished me with samples. 

 This demonstrates that, even if every vastator were killed, the species 

 would be amply maintained. 



Oonfining ourselves to the facts of the case, I am certain that there is 

 abundance to furnish a stock to destroy our crops next year. According 

 to Professor Owen, one single aphis may give rise to a quintUlion during 

 one year, a number which we may write, spell, or pronounce, but which we 

 cannot comprehend. Perhaps we may form a faint notion of a quintillion 

 of aphides when I state that they would form an army which would extend 

 round the globe, and be thirty millions of miles in breadth. This is 

 perhaps an exaggerated account of the rate of increase, yet, under a greatly 

 diminished estimate, it will show that there is plenty left for the next 

 year's brood. 



By the very lowest increase the quantity which might be produced by 

 one aphis is ten billions, and that is certainly much too low, as this 

 number is formed upon the supposition that each aphis only brings forth 

 one litter in ten, whereas I believe that they bring forth many litters. 

 Upon this calculation one aphis now living might give rise to a progeny 

 which would form an army, if there were nothing to destroy them, which 

 would extend completely round the globe, and be a furlong in breadth. 



In greenhouses the green-fly, the Aphis roscB, the aphis of cinerarias, 

 and some other species, are to be found ; but out of doors I have not met 

 with other species this January. » 



During the last month the effects of the vastator of last year have 

 more fully manifested themselves by the rottings of the bulbs of infected 

 turnips, and the extensive rotting of carrots down their central portions. 



With respect to the operations for February, I must refer to my letter 

 of January the first, and to the farmer I would say — Remember that a 

 potato plant, once diseased, is like human beings in its tendency to 

 propagate disease, without the further action of external causes. A tuber 

 from a former diseased plant, though apparently sound, may show the 

 malady without a new attack of the vastator. 



Sets from plants which have never been diseased, and absence of the 

 vastator, will secui-e to the husbandman abundant crop for the future ; but, 

 above all things, let everybody who requires food to eat, be taught the 

 necessity of destroying the vastator. 



Probable Failueb op the Steawbeeet Ceop. 



In my report for January, I stated, upon the authority of Mr. Walker, 

 that the eggs of the vastator were upon the strawberry leaves. Since that 

 repoi't was written, I find that the leaves of that plant have great abundance 

 of eggs everywhere; and I learn, upon inquiry, that the strawberry plants 

 were affected like the potato last autumn. 



