

LIFE HISTORY OF PHYLLOXERA. 249 



SUMMARY OF THE LIFE HISTORY OF PHYLLOXERA. 

 (By R. Dubois.) 



The phylloxera vastatrix is seen under different forms- 

 some above ground, others under ground. These are 

 1st, apterous agamous (above and under ground) ; 2nd> 

 nymptia (under ground) ; 3rd, winged agamous (above 

 ground) and sexed (above ground). These different forms- 

 proceed from a common origin. 



1ST. APTEROUS AGAMOUS. 



The Apterous agamous forms are hatched from the egg of 

 the sexed. They usually appear in the Mediterranean 

 climate in April. > They are easily recognised by their rapid 

 movements, and their pale-yellow, rather grey colour, the 

 length of their legs and antenna, and the rigid hair covering 

 these organs. They crawl on the shoots or travel down on 

 the roots in the soil, according to more or less favorable 

 conditions of the atmosphere. 



(a) Galli cole life. In the first case the insect punctuates 

 the parenchyma of the young leaves, herbaceous tender 

 shoots, and even tendrils,, producing galls, in which it fixes 

 itself and constitutes, after three successive moultings, a 

 laying mother. It then becomes swollen and more volumi- 

 nous, laying a large number of eggs (pseudova) in the pouch 

 thus formed. These eggs hatch after a very short period. 

 The youngs of this second generation crawl in turn on to the 

 top leaves, forming new galls, or travel down on the roots, 

 as the case may be. The multiplication of this gallicole 

 form may continue until the fall of the leaves if circum- 

 stances are favorable. 



(b) Radicole life. The insects penetrating underground 

 fix themselves on the roots, and may be divided into two 

 groups those which, like the gallicole, pass after a series of 

 three moultings to the state of laying mothers, and those 

 which after five moultings reach the state of nymphce. 



1st. Laying mothers very similar to those above ground, 

 lay, without being fecundated, from 25 to 30 pseudova, at the 

 rate of two to three for four or five days, after which they 

 die. The pseudova, hatched eight to ten days after, give 

 birth to young, which may come out of the ground through 

 the natural crevices of the soil, and, carried by the wind, 

 may fix themselves on other roots. This new generation 



