184 BOARD OF AGRICULTURE. [Jan., 



on a branch, and the number of branches on the tree, that there 

 were twelve million plant-lice on that tree ; and it was only one 

 tree of a row similarly infested. To give the reader an approxi- 

 mate idea of the number of insects on the tree, it was stated that 

 were a man to count them singly and as rapidly as he could 

 speak, it would require eleven months' labor at ten hours a day 

 to complete the enumeration. 



Insects are enormously reproductive, and were the progeny 

 of one pair allowed to reproduce without check they would 

 cover, in time, the entire habitable earth. The rapidity of 

 propagation as shown in some insects is, perhaps, without a 

 parallel in the animal world. In order to give some idea of 

 the powers of multiplication of the Colorado potato beetle, 

 the Canadian Entomologist states that all its transformations 

 are effected in fifty days, so that the progeny of a single pair, 

 if allowed to increase without molestation, would amount, in 

 one season, to over sixty millions. Speaking of the power of 

 multiplication shown by plant-lice, or aphids, Dr. Lintner says 

 that Professor Riley, in his studies of the hop vine aphis 

 {PJwrodon humuli) has observed thirteen generations of the 

 species in the year. Now if we assume the average number of 

 young produced by one female to be one hundred, and that 

 every individual attains maturity and produces its full com- 

 plement of young (which, however, never occurs in nature), 

 the number of the twelfth brood alone, not counting those of 

 all the preceding broods of the same year, would be 10,000,000,- 

 000.000,000,000,000 (ten sextillions) of individuals. Where, 

 as in this instance, figures fail to convey any adequate concep- 

 tion of numbers, let us take space and the velocity of light as 

 measures. Were this brood marshaled in line with ten indi- 

 viduals to a linear inch, touching one another, the procession 

 would extend to the sun (a space which light traverses in 

 eight minutes) and beyond it to the nearest fixed star (trav- 

 ersed by light only in six years), and still onward in space 

 beyond the most distant star that the strongest telescope may 

 bring to our view, to a point so inconceivably remote that light 

 could only reach us from it in twenty-five hundred years. The 

 smallest approach to such unchecked multiplication on the part 

 of this insect might paralyze the hop-growing industry. Wliile 

 the aphids may represent the extreme of fecundity, there are 

 thousands of insect species, the unchecked increase of any one 



