250 MANUAL OF MODERN VITICULTURE. 



passes through the same phases as the preceding, and the 

 multiplication continues until the end of October or the 

 beginning of November. 



At that time the laying mothers die, the young ones, 

 recently hatched, spend the winter under the roots in a state 

 of complete torpor. They then assume a brown colour, and 

 become very attenuated. In April the hybernating insect 

 continues the series of agamous generations, and this mode 

 of multiplication may last four years at least. 



2nd. The apterous which do not become laying mothers 

 reach, as we have seen, the state of nympha, after five 

 naoultings, in July. 



2ND. NYMPELE. 



The nymphge have a longer body and a browner colour, 

 and are provided with two winged sheaths of darker colour. 

 After a fortnight the nymphce come out of the ground, and 

 become winged after the last moulting. 



SRD. WINGED AGAMOUS. 



The winged insect resembles a very small fly. It has a 

 long, yellow body, provided with four transparent wings 

 longer than the body and unequal in size, the two upper 

 wings being longer. The winged insect flies, and may be 

 carried by wind to a great distance. It is undoubtedly the 

 principal agent of propagation of the disease to great dis- 

 tances. It stops under the leaves, and lays, without fecun- 

 dation, from three to six pseudova, some being large, others 

 small, from which the sexed are born. 



4TH. SEXED. 



The females are hatched from the large pseudova and the 

 males from the small. These insects are apterous, without 

 beaks or organ of digestion. The female lays one egg, 

 from which are hatched in the following spring new genera- 

 tions of apterous agamous, which we studied previously. 



This egg, which is called winter egg, because it remains 

 under the bark of two-year-old wood (just below the spur of 

 the year) during the whole winter without hatching, was 

 proved by V. Mayet as generally found on stumps which 

 have carried galls many years running. 



We condense in the following table the biological cycle 

 of phylloxera : 



