ON THE AGAMIC REPRODUCTION AND MORPHOLOGY OF APHIS 29 
asks whether it is not probable that, under favourable circumstances, 
the agamic process may be continued throughout the winter. The 
average length of life of his Aphédes was thirty days, or a little 
more; but the representative of the ninth generation lived from 
September 29th to December roth, or eighty-one days. Like those 
of preceding observers, Duvau’s researches clearly show the influence 
of temperature on the fecundity of the viviparous Aphzs. 
It is in Morren’s in many respects valuable paper on the Aphzs 
Persice, published in the ‘Annales des Sciences Naturelles’ for 1836, 
that the germs of the two most notable errors which have crept 
into the natural history of the Aphzdes may be found. At p. 76 the 
following passage occurs !:— 
“The influence of temperature on these animals is obvious; in 
other Aphides, and under ordinary circumstances, the female lays 
her eggs when she has wings and after copulation with the male, 
who is winged at the same epoch. Oviposition takes place in this 
manner at the seventh generation for some—at the ninth, or 
even at the eleventh, for others; before it, female larve alone are 
produced.” 
Morren here supposes himself to be simply repeating what he has 
read. But so far as I am acquainted with the older literature of the 
Aphides, he is entirely mistaken. I can nowhere discover that either 
Réaumur, Bonnet, Degeer,2 Kyber, or Duvau have observed winged 
oviparous females in any species; nor do the statements of any of 
these observers justify the belief that the sexual forms always appear 
after a certain number of generations. All that Bonnet affirms is, 
that his particular experiments came to an end accidentally after the 
production of a certain number of agamic generations, which is, of 
course, quite another matter. 
When Morren details his own observations, his results are in exact 
accordance with those of the older observers. “In the Aphis Persice,” 
says he, “I have very frequently seen (and I have shown the phe- 
nomenon to my colleague, M. Burgraeve) that the winged and fer- 
tilizable female never contained ova and never laid any, but that she 
contained little living Ap/zdes, which are born fully developed, and 
1 “Tinfluence de la température sur ces animaux est manifeste ; chez les autres pucerons, 
et dans les circonstances ordinaires, la femelle pond des ceufs lorsqu’elle est ailée, et aprés 
un accouplement avec le male ailé & la méme €époque. Cette ponte se fait ainsi a la septiéme 
génération pour les uns, 4 Ja neuvieme ou méme 4 la onzi¢me pour les autres ; avant elle, il y 
a seulement naissance de femelles naissant 4 I’ état de larves.” —Morren, 4. ¢. 
2 Degeer’s account of the gall-forming Puceron du Pin is an apparent exception to this 
statement, but I believe only an apparent one. Degeer expressly states that he never saw 
the winged form of this species in copulation ; and, besides, it is not a true Aphis at all. 
