458 



Marvels of Insect Life. 



at the juices. As in the grcen-liy, there are several forms and conditions of the 

 vine-aphis. Those feeding upon the roots are mostly wingless females of a pale 

 vellow or dull-brown colour, with antennae of three joints, rather short legs, and 

 imperfect eyes. They attach themselves to newly formed roots, into which they 

 thrust the fine proboscis, and suck at the sap. This causes the swelling up of the root, 

 which bursts its bark, reveahng yellowish masses of a lac-like material. The roots 

 being unable to do their work properly, the upper shoots become stunted, the leaves 

 turn yellow, the roots die, and there is an end of the plant. When the plant is 

 dead the vine-aphis leaves it, and migrates to healthy plants within reach ; so 

 that one infected plant becomes the centre from which a district is attacked. 

 During the winter these root-females remain inactive, but in spring they wander 

 to newly formed roots, and each lays from thirty to forty eggs in several batches. 



These hatch in from live to twelve days, and 

 the wingless young undergo several changes 

 of skin ; but they are soon adult, when thev 

 also lay eggs which in turn produce wingless 

 females, and this process is in the main 

 repeated six or eight times throughout the 

 summer. About midsummer, however, there 

 is some change. Some of the eggs produce 

 individuals that develop wings and perfect 

 eves and longer legs. These crawl up the 

 stems whilst still immature, and when their 

 wings are developed and free they may fly 

 away to infect other vines. This they 

 accomplish bv laving a few eggs on the 

 leaf-buds or the under side of the leaf. These 

 eggs are not equal in size, and thev differ 

 in character, the larger ones producing 

 mature females, and the smaller mature 

 males. Both sexes of these are produced 

 solely for breeding purposes, for neither of 

 them possess the means of feeding. They 

 pair, and the females lay eggs singly under the loose bark of the vine. These eggs 

 remain through the winter and hatch in the following spring, all alike {:)roducing 

 wingless fertile females capable of producing other wingless females, and so on for 

 several generations. The first spring brood may remain on the leaves and attack 

 them, producing galls in the form of wart-like excrescences on the u})piM- side of 

 the leaf with an entrance slit on the under side. The\' produce young inside the 

 gall, and these migrate to the roots. 



To minimize the destruction caused by this pest, and taking advantage of the 

 fact that in America the aphis scarcely attacks the roots, vines are now being 

 grown that have been grafted upon stocks of the American species, which have 

 stronger roots and a more hardy constitution, owing ])robably to the fact that 

 they have been cultivated for a mu(-h shorter pcM-iod. 



Photo bv] 



Oak Phylloxera. 



[IV--. West. 



A few of the eggs from one of the circles shown in the 

 next photograph, magnified to fifty times the actual size. 

 They hatch in the course of a few hours after being 

 deposited. 



