TRUE ORTHOPTERA 



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less, and give birth to living young, or, as in the genus Phylloxera, lay eggs from 

 which the young subsequently develop. The new brood, thus produced partheno- 

 genetically, resembles the one from which it has sprung, and gives rise to a fresh 

 brood in a similar manner. As many as nine or ten generations may succeed one 

 another in this way during the course of the season, before the appearance in the 

 autumn of the last or sexual generation. The brood preceding and giving rise to 

 the latter often consists of winged individuals, which leave the plant on which they 



VINB PHYHOXERA (much enlarged). 



i and 2. The wingless form found on the root, seen from above and below ; 3. The same from the side ; 4. Its 

 piercing organs ; 5. Winged individual ; 6. Rootlets of the vine, with swellings caused by the Phylloxera ; 

 7. An old root stock, with (8) hibernating individuals. 



were born and fly to some other. In the genus Phylloxera, the males are wingless 

 and each of the sexual females lays but a single egg, known as the winter egg; but 

 in other forms the number is often much greater. Each of the parthenogenetic 

 females of 'Phylloxera may in the course of its life lay as many as two hundred eggs, 

 and each of the viviparous females of other species may give birth before they die 

 to forty or fifty young. When we consider that there are several generations every 

 year, it can be easily understood how it is that these insects spread with such rapidity; 



