28 ON THE AGAMIC REPRODUCTION AND MORPHOLOGY OF APHIS 
reproductive power is practically indefinite, and is chiefly, if not 
wholly, dependent on conditions of temperature and nutrition. He 
says (p. 34) :— 
“T never saw a male in copulation with a winged female in any 
species. It was always the apterous females which were attacked 
by the males; for in many species apterous females remain among 
the families. Neither have I ever seen winged females lay eggs. 
This has, indeed, been already remarked by Degeer.” 
In a note Kyber adds the caution, that he has not observed more 
than twenty species in copulation, and does not wish to extend his 
conclusions beyond these. 
The fourth note to this important paper contains the following 
remarkable observation :— . “The winged females especially, in 
which, even after frost has set in, fully-formed young may always be 
found, when the apterous females of the same family have long been 
laying eggs. On the 21st November, 1812, I still had winged Aphzdes 
(Haberblattlause) in my possession, although the apterous ones had 
copulated and laid their eggs in September—a remarkable circum- 
stance, without doubt, and one whence important conclusions with 
regard to the mode of propagation of the Apfzdes are likely to flow. 
Possibly many winged females survive the winter, together with their 
young” (p. 10). 
In other parts of his memoir (p. 2 e¢ seg.), Kyber adduces strong 
evidence in favour of the hybernation of the viviparous forms of some 
species, which Degeer had already proved to be the case with respect 
to the remarkable “ Puceron des Galles du Sapin.” 
In the Aphzs Dianth?, Kyber was never able to observe either 
copulation or oviposition; and so far from there being any natural 
term to the number of asexual broods which succeed one another, he 
states that he raised viviparous broods of both this species and 
A. Rose for four consecutive years, without any intervention of males 
or oviparous females, and that the energy of the power of agamic 
reproduction was at the end of that period undiminished. The 
rapidity of the agamic prolification throughout the whole period was 
directly proportional to the amount of warmth and food supplied. 
Duvau, in his already cited “Nouvelles Recherches sur l'histoire 
naturelle des Pucerons,” read before the French Academy of Sciences 
in 1825, states that he had carried the series of successive agamic 
generations in the Aphzs of the Bean (féve) to eleven, which was one 
more than Bonnet had obtained. The process lasted seven months, 
and the last young was born on the 27th December, but died on the 
29th. Duvau, however, kept some alive until January, and naturally 
