THE PHYLLOXERA VASTATRIX. 



Ill 



which the largest are female pggs and the smaller males. But the insects which 

 issue from them are remarkable in more respects than one. From the female 

 eggs are produced females without wings, and equally males without wings from 

 the male eggs. They are incapable of feeding, for neither has a sucker. From 

 these males and females proceed a fresh laying of eggs, or rather of egg, for 

 the female only lays one solitary egg, which is not yellow, but more or less of 

 a sombre green, and is very difficult to perceive on the bark, where it is fixed 

 by a small hook. It passes the winter thus, and in spring a wingless individual 

 is hatched exactly resembling those on the roots, but with a very long sucker. 

 This vernal individual is very fertile, containing from twenty to twenty-four 

 ovaries or reservoirs full of eggs. Its descendants produce eggs without the 

 intervention of males, some of them fixing themselves on the leaves and pro- 

 ducing galls (figs. 45 and 46), the others reaching the roots and renewing the 



Fig. 48. PHYLLOXERA VASTATRIX : a, Imago of short-bodied root form, 

 formerly supposed to be the male ; b, winged female, upper surface ; c, ditto, 

 lower surface. Very greatly enlarged. 



subterranean race. How long the race may be propagated in this way, without 

 the intervention of the sexual males and females above spoken of, is not known. 

 .But as the continual renewal of the race proceeds, each brood becomes less and 

 less fertile, by a reduction in the number of the egg-bearing tubes or ovarian 

 reservoirs. The winged female, fertile without the intervention of a male, only 

 lays a small number of eggs from four to ten. At last the progress ends by 

 the sexual female having no more than a single ovarian reservoir and a single 

 e^'g, which will be sterile if there is no male to fertilise ic. In this way the 

 biugle egg which terminates the Phylloxerian cycle is reached. 



''The above is the account given by Professor Balbiani and Professor Maurice 

 Girard of the evolution of the Phylloxera. Whether their views are well founded 

 or not remains to be seen. They are the authors who have paid most attention 

 to the subject, and to whose opinion much weight is attached. Their solution of 



