MODERN YITICULTURAL METHODS. 607 



The life histoiy of Piiylloxera is reinarkuble and somewhat com- 

 plicated. Owing- to the great difficulties^ of observing so minute an 

 insect of chiefly subten-anean habits, the cycle was not so quickly 

 discovered as would be the case with insects more readily observed, 

 and its life histoiy was for long unwritten. Thanks to the unweaiying- 

 researches — principally of French and Ajuericjui investigators — we 

 now know this stoiy fairly well. 



The eggSi which tide the insects over the cold of winter are for 

 this reason known as ■■winter-eggs." They are laid on the wood 

 of the vine, particularly on the older wood. Prol}al!ly they may have 

 originally been also deposited on the younger canes, but as these 

 are removed annually at pruning time, and destroyed, the instinct tO' 

 seek the more secure positions on the vine stock became hereditaiy.. 

 Cold of climates much more rigoroTis than our own does not impair 

 the vitality of these eggs. The warmth of spring or early summer 

 hatches them out. If the vine be of American origin, the newly- 

 hatclied insects form galls on the leaves. If, on the other hand, the 

 vine is -wdiat is known as European, then the insects descend to the 

 roots, where several generations — the progeny of '" laying-mothers" — 

 carry on their work of silent destruction. About the middle, or to- 

 wards the end of the summer, some of these subterranean insects 

 begin to sliow signs of wing development. These are then known as 

 "nymphs." This characteristic is especially marked when they have 

 exhausted their food supply by destroying the fc'eding roots. After 

 several moults, the wings become sufficiently developed, and the 

 insects fly and are cai-]-ied in the direction of the prevailing winds to 

 set up new colonies of infection in the same or an adjoining vineyard. 

 Having reached a suitable spot, these winged migrants lay eggs on 

 the vine selected. These eggs differ in size. From the larger, females 

 are produced, while the smaller give rise to males. This is the first 

 appearance in the cycle of the two sexes. These insects have no 

 organs of nutrition. They pair, and the result of the union is the 

 fe)-tilisation of the winter-egg already described. The tiny male 

 insect immediately dies. His partner only survives him till the 

 important function of egg-laying has been accomplished. 



Tlie effect of the puncture made by the insect's proboscis is to 

 cause the rootlet to swell up and cuiwe over in a peculiar manner, 

 and resemble frequently a bird's beak. Not only is the plant food 

 removed by the insects, but the puncture sets up a remarkable irrita- 

 tion, that causes mortification of the tissues. To a skilled observer, 

 often the first indication of attack to the vine is an abnormal crop. 

 As if the plant were conscious that it cannot long survive, it sets to 

 work to make provision for the production of its seed, in order to 

 secure the perpetuation of the species. New roots are rapidly thrown 

 out, and the vine seems even more vigorous than ever. But it is 

 only for a time. The unequal stmggle cannot long be maintained. 

 After vintage the leaves change colour and fall early. Next season, 

 growth is stunted, and ere long the vine dies, and the pest spreads 

 further afield. 



When it was definitely decided that Piiylloxera had been intro- 

 duced to Europe on some of ttie native American vines, some of the 

 keener viticultm-al scientists of France concluded tliat there must 

 be some vines in the native home of the insect that could withstand 



