June 22, 1883. 



SCIENCE. 



577 



sitious have beeu sent to us of late _yeai's with 

 a request that we assist the proposers in pre- 

 senting their claims to the Fi'ench government. 

 In almost every instance the proposers have 

 shown an absolute lack of experience, both as 

 to the insect and as to the methods thej' 

 recommend. 



The question of the winter egg, so called, 

 has again occupied much of the attention of 

 the commission, which places great confidence 

 in the researches in regard to it of one of its 

 eminent members, Balbiani, who has been in- 

 structed to continue his investigations. In 

 reference to this egg, and the importance of 

 destroying it, there has, of late, been much 

 discussion in France ; and we may repeat our 

 answer to the following question, recently put 

 to us hy one of the first French investigators 

 into the life-historj- of Phylloxera : — 



'■^ L'oeuf soi-disant d'hiver de M. Balbiani 

 est-il indispensable a la reproduction du Phyl- 

 loxera, ou Men la reproduction agame vous 

 parait-elle piossible durant plusieurs annees ou 

 mhne indejiniment?" 



Our reply was, that the impregnated egg (we 

 prefer this term to ' winter egg ') is indispen- 

 sable to the continued reproduction of Phyl- 

 loxera, and that normally- it is produced 

 aunuallj- in the cj'cle of the insect's life ; but 

 that agamic multiplication may, under favoring 

 conditions, extend to the third or fourth j'ear, 

 and, for aught we know, longer. 



In reading over Targioni-Tozzetti's criticism 

 of Balbiani, and the latter's repl.y, in late num- 

 bers of the Comptes rendus de I'acadimie, we 

 felt, that, so far as our own observations and 

 experiments have gone, both were in a degree 

 right, and both wrong. There is no question 

 but that Balbiani is essentially right in his con- 

 clusion as to the necessitj- for the impregnated 

 egg at some period during the annual develop- 

 ment, under the conditions of our changing 

 seasons. All the facts ascertained, as well as 

 all analogy from what is known of the life- 

 historj- of other species of the familj-, point 

 to the accuracy of that conclusion. Yet ex- 

 periments enough are on record to show, that, 

 where the conditions of csxvly spring and sum- 

 mer are artificially maintained, agamic repro- 

 duction in aphides may be greatl.y extended, 

 and even go on to the third or fourth year. 



Of course, this possibility of such continued 

 agamic multiplication does not change the 

 practical fact of what does take place in an or-- 

 dinary year under ordinary seasonal changes. 

 Balbiani, therefore, is theoretically quite right 

 in insisting on the importance of the destruc- 

 tion of his winter egg. Just here, however, Is 



where we shall have to differ from him as to 

 the practical value of attempts to do so, and 

 for the following reasons : — 



It is a universally- conceded fact, that the 

 species hibernates chieflj' in the dormant larval 

 state underground. Now, even supposing that 

 every so-called winter egg could be destroj'ed, 

 we know positively that the vines would still 

 be infested, and that new impregnated eggs 

 would again occur the ensuing fall or winter. 

 Therefore, even on Balbiani's belief, these eggs 

 would have to be annihilated for at least two 

 consecutive years to do any good. But, unfor- 

 tuuatel}', all methods of annihilation heretofore 

 proposed have proved impracticable, and, in 

 fact, impossible.^ Decortication must always 

 be but partially successful, as the eggs are not 

 confined to the loose bark or to the older por- 

 tions of the vines. Moreover, our researches 

 in this country (and it seems to us that ex- 

 perience in Europe corroborates them) show 

 conclusively that this impregnated egg is not 

 necessarilj- a winter egg, for it is extremely 

 rare, and difficult to discover, during winter, 

 or at any time : hence, and for the reason that 

 larval hibernation prevails, we are justified in 

 one or the other of the following conclusions : — 



1°. That the sexual females do not necessa- 

 rilj' confine the impregnated egg to the stems 

 and branches, but lay them also at the base of 

 the vine, or even beneath the ground ; 2°. That 

 hypogean, apterous females also produce the 

 sexed individuals underground ; 3°. That the 

 impregnated egg hatches the same season that 

 it is laid. 



Now, there are certain facts of experience that 

 would give some warrant to all three of these 

 conclusions, the first and second being fiill.y 

 justified by facts recorded by Balbiani and our- 

 selves. The third statement we have proved 

 true with Phj'Uoxera Rileyi ; and M. P. Graels 

 has also proved it for P. vastatrix in Spain (see 

 Amer.nat., 1881, p. 483). 



Thus we have little faith in the results of 

 decortication ; and we have already expressed 

 much the same views in the American nat- 

 uralist, in our eighth Missouri report, and in 

 our report to the Department of agriculture for 

 1878, p. 83. 



With regard to the use of American vines as 

 stocks on which to graft the more susceptible 

 French vines, the commission admits the suc- 

 cess of the former in rich or deep soils, but 

 concludes that they leave something yet to be 



^ The eggs, in the rare cases where they are found, arc con- 

 cealed as much as jDossible in minute cracks and crevices, so 

 that mechanical decortication cannot well reach them all ; while 

 the application of heat, as by torches, would not destroy them 

 all unless intense enough to injure the vines. 



