134 



and after verj- careful and i^ersistent investigation, in which I have had 

 the cooperation of several of mj assistants, the question has been fully 

 and thoroughly settled. 



The facts in the life history of this insect, 

 therefore, may be summed up as follows: 

 Hibernating at the present season of the 

 year, the little glossy, black, ovoid eggs of 

 the species are found attached to the term- 

 inal twigs, and especially in the more or less 

 protected crevices around the buds, of dif- 

 ferent varieties and species of Prunus, both 

 wild and cultivated. From tbis winter-egg 

 there hatches a stem-mother (Fig. 30), which 

 is characterized by being somewhat stouter, 

 with shorter legs and honey tubes than in 

 the individuals of any other generation. 



Three parthenogenetic generations are 

 produced upon Prunus, the third becoming 

 winged (Fig. 31). This last is what my late friend Lichtenstein called 

 the ])seudogyna or migrant, and it instinctively flies to the hop-plant, 

 which is entirelj^ free from attack during the development of the three 

 generations upon Plum. A number of parthenogenetic generations are 



Fig. 32. Phorodonhumuli, true sexual 

 female, enlarged (original). 



Fio. 33. Phorodon hvmuK, male, enlarged (original). 



produced upon the Hop until in autumn, and particularly during thp 

 month of September winged females are again produced. This is the 

 pt(])ifera of Lichtenstein or return migrant, and she instinctively re- 

 turns to the Plum. Here she at once settles and in the course of a 

 few days, according as the weather i)ermits, i)roduces some three or 

 more young. These are destined never to become winged and are true 



