12 INSECT TRANSFORMATIONS. 



air by this same mist.'* c The farmer,' says Keith, 

 1 supposes these insects are wafted to him on the 

 east wind, while they are only generated in the ex- 

 travasated juices as forming a proper nidus for their 

 eggs. 'I A more detailed account, however, is given 

 by the late Dr Mason Good, and as he speaks in 

 part from personal observation, and was not only 

 one of the most learned men of his time, but an ex- 

 cellent general naturalist, his testimony merits every 

 attention : 



* That the atmosphere,' says Dr Good, ( is freight- 

 ed with myriads of insect eggs that elude our senses, 

 and that such eggs, when they meet with a proper bed, 

 are hatched in a few hours into a perfect form, is clear 

 to any one who has attended to the rapid and wonder- 

 ful effects of what, in common language, is called a 

 blight upon plantations and gardens. 1 have seen, as 

 probably many who read this work have also, a hop- 

 ground completely overrun and desolated by the aphis 

 humuli, or hop green-louse, within twelve hours after 

 a honey-dew (which is a peculiar haze or mist loaded 

 with poisonous miasm) has slowly swept through the 

 plantation, and stimulated the leaves of the hop to the 

 morbid secretion of a saccharine and viscid juice, 

 which, while it destroys the young shoots by exhaus- 

 tion, renders them a favourite resort for this insect, 

 and a cherishing nidus for myriads of little dots that 

 are its eggs. The latter are hatched within eight and 

 forty hours after their deposit, and succeeded by hosts 

 of other eggs of the same kind; or, if the blight take 

 place in an early part of the autumn, by hosts of the 

 young insects produced viviparously; for, in different 

 seasons of the year, the aphis breeds both ways. 

 Now it is highly probable that there are minute 



* Loudon's Mag. of Nat. Hist, i, 180. 

 f Keith's Physiological Botany, ii, 486. 



