MY GARDEN. 



that the females propagate to an unknown extent without impregna- 

 tion ; and although I have kept myriads of the Aphis vastator for 

 observation, I have never seen either an egg or a male. We are in 

 the habit of looking to astronomy for numbers beyond the capacity of 

 man to realize, but the multiplication of aphides affords a more 

 astounding illustration. A single aphis produces about ten every ten 

 days, and these again give birth to ten ; therefore to represent the 

 number of the progeny of one of these creatures for the space of 

 one year, thirty-six figures placed in a row would be required. As 

 the distance in miles between the earth and the sun is represented by 

 only ten figures, and as seventeen figures would represent the number 

 of aphides required to form a line between the same bodies, we may 

 form a kind of indefinite vision of the immensity of the power of mul- 

 tiplication possessed by aphides, and have a dim idea of the rapid 

 manner in which they can cover vegetation when they appear. 



FIG. 1045. Aphis vastator, highly magnified. 



I have in my cabinet about 150 species, and I have traced a single 

 species over sixty plants. Koch has given in his work 396 figures, 

 and Boisduval has noticed 163 species. Nevertheless there is con- 

 siderable confusion about many of the names. The one which I 

 named A. vastator was called by Curtis A. rapes, and both Mr. Curtis 

 and myself considered that it was the same species. By some 

 learned entomologists it was called, but I think wrongly, A. nimicis, 

 and now some consider that it is A. diantki. I have figured a drawing 

 of one of my own specimens from the "Year-book of Facts" of 1850 



