I'ACKAUD.] 



THE GRAPE PHYLLOXERA. 



783 



except in Gonnecticut, where it has been found by Mr. Riley. I received 

 it several years ago from Philadelphia, and it has done much damage 

 in the Middle and Western States, while it is known to affect vines in 

 California. As we are destined to be greatly annoyed by it, a brief 

 description condensed from the excellent account by Mr. Riley in his 

 sixth, seventh, and eighth report of the insect in its two forms, may be 

 timely. The insect was first found in this country, and was described 

 by Dr. Fitch in 1856, under the name of Pempliigus vitifolkv. Its proper 

 name is Phylloxera ritifolice, though most authors speak of it as Phyl- 

 loxera vastatrix. It exists in two forms, one raising irregular galls on 

 the leaves, and the other forming small swellings on the rootlets. The 

 root-form is both wingless and winged, the latter very rare. The leaf- 

 form is said to be always wingless. 



The wingless female of the leaf-form lays, on an average, 200 eggs, 

 and sometimes 500. There are perhaps five generations in a year. This 

 leaf-form produces round, irregular galls, sometimes as large as a pea, 

 but it does little damage compared with the root-form, which is much 

 more abundant than the leaf-form (especially on native vines) in France, 

 where its ravages have been so alarming that the French government 

 have offered a reward of 300,000 francs for a simple available remedy. 



The leaf-form descends to the roots in the autumn, and there hyber- 

 nates. The larvte of the root-form are at first smooth and like the 

 young of the leaf-form, but afterward molt and become warty, so as 

 to become readily distinguishable from them. 



Professor Riley and certain French observers have lately proved that 

 the gall-i)roducers (or the leaf-form) come from the impregnated or 

 winter egg. 



The winged females begin to appear in July, but are most abundant 

 in August and September. Like the wingless females, they reproduce 

 by budding (parthenogenesis), the eggs not being fertilized by males, 

 no males being in existence. Having isguM frQlfl tlie grQand whijjg in 

 the pupa state, they rise in 

 the air, and spread to new 

 vineyards, where they lay 

 two or three, someti mes eight 

 eggs. These eggs are of two 

 sizes, and, in about a fort- 

 night, from the larger eggs 

 are hatched wingless true 

 sexual females, and from the 

 smaller eggs wingless males. 

 "The abdomen of the fe- 

 male, after impregnation, en- 

 larges somewhat, and she is 

 soon delivered of a solitary 

 egg, which differs from the 

 ordinary eggs of the parthe- 

 nogenetic mother, only in 

 becoming somewhat darker. Fig. 

 This impregnated egg gives 

 birth to a young louse, which 

 becomes a virginal, egg- bear- 

 ing, wingless mother, and 

 thus recommences the cycle 

 of the species' evolution. But one of the most important discoveries of 

 Balbiani is that, during the latter part of the season, many of the wing- 



gaUfccola. a, h, newly-hatched 

 larva, ventral and dorsal view c, egg ; d, section 

 of gall ; e, swelling of tendril ; /, g, h, mother gall- 

 louse, lateral, dorsal, and ventral views ; /, her 

 antenna ; j, her two-jointed tarsus. The figure 

 on the side of each enlarged drawing represents 

 the natural size. (After Riley.), 



