154 London Insects. 



warm day in spring or early summer an Aphis is 

 hatched, and almost instantly has a family of a 

 hundred females born alive, each of which, without 

 an unnecessary loss of a day, follows her mother's 

 example. The granddaughters do the same, till ten 

 generations have been born alive. The result, sup- 

 posing all to live, is i x 100 x 100, &c., &c., until in 

 the tenth, not the last generation of the year, the 

 family numbers 1,000,000,000,000,000,000 a quin- 

 tillion : the figures are Professor Owen's.* Then, 

 and this is strangest of all, comes the eleventh 

 generation. When vegetation is rank in spring and 

 summer, the generations of Green Fly, which have 

 to make hay while the sun shines, cannot spare 

 time for such a slow process as being hatched from 

 eggs. That can wait till there is a use for it, and 

 later in the year the use comes. The Aphis is not 

 hardy enough to survive a sharp winter, and so the 

 eleventh generation of the season the whole story 

 sounds too like a fairy tale the eleventh generation 

 is born " oviparous." 



When their turn comes to have families, instead 

 of giving birth to living babies they lay eggs, some 

 of which are sure to hatch next spring, and thus save 

 from extinction the race which are the milch cows of 

 the Ants. 



We can see our way more clearly again when we 

 leave the quagmire of the Hemiptera and come to 

 the Orthoptera and Coleoptera Grasshoppers, &c., and 

 Beetles. 



One can, when one meets with it, recognise an 

 insect with thick sheaths (/eoXeo?) as upper wings 

 covering a lighter transparent pair, and can under- 

 stand that there is a difference between those which 

 * " Invertebrate Anatomy," Lecture XVIII. 



