GRAPE PHYLLOXERA. 



343 



NATURAL HISTORY. 



The generic name of tLis little devastator {PliijUoxera) comes from the 

 Greek, and means "leaf-withering.'' The genus is characterized by having 

 three-jointed antennse, the terminal joint much the longest {see i,fig. 2), and 

 the wings overlapping flat on the back in repose {see g, jig. 4). 



It belongs to the sub-order Hemiptera, or to the bugs ; but these are Homop- 

 terous, the wings not being thickened at the base, giving the appearance of 

 half-wings, like the squash bug, but are homogeneous throughout. In cemmon 

 with all bugs, these are provided with a strong sucking beak {see a, Jig. 2). 



This insect belongs to the family Aphidce, or plant-louse family, with near 

 affinities to the Coccidce, or bark-louse family. Yet its resemblance to this lower 

 family is confined mostly to the larval state, and this early resemblance to 

 lower forms is, as first shown by the great and lamented Agassiz, true of all 

 animals. 



TWO FORMS. 



As already intimated, there are two distinct forms of this insect, which dif- 

 fer much in their appearance, and totally in their habits. These we shall 

 denote from the place where they respectively work, as the leaf form and the 

 root form. 



THE LEAF FORM. 



In early summer, soon after the leaves appear, the wee yellow lice, with 



quite fully developed legs, antenna and 

 beak, commence to puncture the leaves. 

 Thus irritated, the leaf commences 

 at this point an excessive growth 

 downward, forming a cup-shaped cav- 

 ity, in which the louse is imprisoned, 

 never to escape. There is an open 

 mouth to this cavity at first, but soon 

 the edges close above the louse. These 

 galls are quite large, and later in the 

 season as they become very abundant, 

 can hardly fail to attract the atten- 

 tion even of the most unobserving 

 {see fig. 1). The lower side of the 

 leaf is covered with bunches, large as 

 a small pea, while the upper side has 

 * FIG. 1.— UKDEE SIDE OP LEAP, sHowiKG GALLS, corresponumg Ciepressious. 

 These young lice {see a and i in fig. 2) grow rapidly, become dull orange, 

 and as they begin to develop, — these are all females, — they become broader and 

 Beem more clumsy {see /, g, and h in fig. 2), from the fact that the legs, an- 

 tennae and beak do not keep pace with the growth of the other parts, and seem 

 quite abortive, though the tarsi {see j in fig. 2) — a name given to the last 

 joints of the feet of insects — are now two-jointed, where as before they were 

 but single-jointed. Thus shut out from the gaze of all intrusive observers, the 

 mother louse has a rare chance to concoct mischief, Avhich she is not loath to 

 improve, as is clearly indicated in the significant fact that she is soon sur- 



*The cnts illuf^tratirg this article are from the ekillful and accurate pencil of Prof. C. V. Riley, State En- 

 tomologist of Migsonri. 



