OF THE STATE ENTOMOLOGIST. 69* 



(11) There is matter of tlispute among authors as to the number of generations an- 

 nually produced, and it is dilHeult to ascertain tiie number. I have, however, experiment- 

 ally proved byartiticial hreedino' this winter, that at least five generations may follow 

 each other without the appearance of form [i which is destined to become winged. I 

 have kept, in large darkened vases, a number of Phylloxene feeding and breeding on- 

 Clinton roots, which, from the tendency to sprout, furnish sufficient nourishment with- 

 out requiring very frequent renewal, if kept lightly mixed with moist soil. These lice 

 were taken in November when in the hibernating larval condition, in which they would' 

 be the following spring when they naturally awaken from their torpor and commence 

 multiplying;. Though kept in my office, in which the temperature was only comfortably 

 warm during the day, and sometimes sank nearly to about freezing point during the 

 night, they have continued to grow and multiply. In order to ascertain the exact 

 number of generations that followed each other, I separated some of the first depos- 

 ited ^gg^. and placed them in glass test-tubes, partly tilled with earth, and furnished 

 with short but thick pieces of Clinton root. As soon as the lice from these eggs be- 

 came mothers and laid, their first eggs were again separated, and this process went on 

 till, on the first of April, when plant-life was still dormant out-doors, I had the fifth 

 generation of lice, which, owing to the adding of too much moisture to the tubes, died 

 and rotted, and thus prevented the continuation of accurate notes. On the third of 

 April, however, in examining the large vases, several pupas were met with, and on the 

 10th of the same month I hud winged females in my office, when, on account of the 

 lateness of the season, and as I know from actual observation, the insects out-doors had- 

 not yet awakened from their winter lethargy. 



Signoret, in his first work on •'■ Le Phylloxera de la Vigne"" {Afin. de la Soc. Ent. de 

 France, 1869, p. 575), referred to the rapid multiplication of the Aphides, repeating the 

 well-known statement that at least nine generations are produced in the space of three 

 months. Yet he has lately {Comptes Rendus dc I' Ac. des Sc, Aug. 4, 1873) endeavored^ 

 to make out that there are but about two generations in the course of the year. In re- 

 ality the eggs often hatch in warm weather within a week after deposition, and the lice 

 commence depositing at this season, when they are 10 or 12 days old — the rapidity of' 

 increase depending on the temperature, and the process coming to a stand-still in winter. 



Similarly, there has been some dispute as to the number of molts which the indi- 

 vidual undergoes, and Signoret {loc. cit.) by an un wai'rantable mixing and fusing of two 

 distinct generations, makes out no less than six. In the mother form (a) ofradieieola,. 

 there are but three molts, as recorded by Cornu, and as I have repeatedly proved this 

 winter, by enclosing a single newlj'-hatched louse in a tight glass tube along with a- 

 piece of root first carefully examined to see that no other lice or exuvias were upon it. 

 By the time such an individual has become a mother and attained maturity, three dis- 

 tinct cast-off skins will be found in her immediate vicinity, if she has not been disturbed 

 during growth — the skins adhering to the root by the outstretched and forsaken leg- 

 coverings. Cornu has found the same number (three) of exuviae in the leaf galls, thus 

 indicating, as would be expected, that galkecola goes through the same number of 

 molts as its root-inhabiting analogue. It is possible that the winged form undergoes 

 more than three molts, though there have been no definite observations on this point, 

 as they are necessarily dithcnlt. 



(12) Throughout the winter I have been placing young root-lice, as they hatched,, 

 upon the newly forming leaves of some potted Clintons, Delawares and Eumelans grown 

 for the purpose. On the 17th of January, after an absence of four days at Hannibal, L 

 was fairly delighted by the discovery of a solitary, partially formed gall on one of the 

 lower leaves. It must necessarily have been formed by a young root-louse, either from, 

 those placed on the leaves, or from those hatched on the roots of the same vine ; for the 



