APHIDES OF THE ROSE. 175 



by the calculations of Reaumur, that one Aphis may be the 

 progenitor of 5,904,900,000, descendants. 



The above, which is the least difficult method, certainly, of 

 accounting for the presence of these Insect swarms, would 

 seem also the most easily ascertainable ; yet the popular theory 

 of their being wind-conveyed has had its advocates among the 

 learned, as well as its believers among the simple. Nor indeed 

 is it very unusual for learned theorists to go far and wide, and 

 high and deep, in search of truths which, in nine cases out of 

 ten, they could scarcely have failed to discover, by looking a 

 little more closely into the things on which they are pleased 

 to speculate. 



Now suppose we do this with the leaf-buds of a rose-bush, 

 which, early as it is, we shall find already occupied by Aphis 

 tenantry, such as have recently emerged from minute black 

 eggs, deposited last autumn on the branches. These are all 

 green, of small size, and without wings, but later (towards the 

 end of May) a single flower-bud is likely to present us with 

 two or three kinds of these infesting sap-suckers, differing in 

 size, form, and colour. We shall, therefore, venture to anti- 

 cipate the appearance of summer rose-buds, and, with them, 

 that of the numerous descendants which are sure, by that 

 time, to have sprung from the race of Aphides now in being 

 not, as these, from the egg, but after the manner of viviparous 

 animals. This may seem a strange anomaly, but there are 

 things to tell of Aphis economy stranger still. 



