94 DESTRUCTIVE INSECTS OF VICTORIA: 



"Ui3on the Holly -liock Dug-es found, at tlie same time, 

 individuals presenting almost all shades of colour, a cir- 

 cumstance probably connected with some peculiarity in 

 the nutrition derived from that plant. On the vine, Dr. 

 Johnston found the colour to vary in intensity in different 

 individuals. So far as our own observation goes, the 

 rusty colour is an indication of greater maturity than the 

 green. This, and most if not all the species of the genus, 

 spins a web on the back of the leaves of the finest and 

 most delicate texture. The threads of its web are secreted 

 from a conical nipple situated underneath, and very near 

 the extremity of the abdomen. They are drawn out and 

 guided by the motions of the insect, and by the action of 

 the minute claws and hairs of the legs, which seem to be 

 only used for this purpose. The threads are so slender 

 that we fail to see them, even with the assistance of a 

 magnifier, until after they are woven into a web, or net- 

 w^ork. In the construction of this web all the feet are 

 moved mth great agility, but the movements of the mite 

 itself are not quick, and it moves with difficulty over 

 smooth and polished surfaces, as over glass. Upon leaves, 

 especially on the under side of them, it finds a better hold, 

 for, supported on the bristles that extend beyond the claw, 

 it spins its web, affixing the threads to the prominences 

 and hairs of the leaf; and under this shelter a colony, con- 

 sisting of many of both sexes in maturity, and young in all 

 their stages, feed and mulitply with rapidity. 



" The plant soon shows the influence of their presence in 

 its sickly yellow hue (see Plate X., Fig. 6). The sap is 

 sucked by myriad insect mouths from the vessels of the 

 leaf, and its pores are checked by excremental fluids. 

 The mode in which they feed is by eating their way into 

 the leaf with their nipping mandibles (see Plate X., 

 Fig. 5), and then plunging in their barbed suckers, and 

 sucking the juice. 



" The egg of this mite is spherical, colourless, and propor- 

 tionately large. The larva which comes from it is minute, 

 transparent, and in shape not unlike the parent, but it has 

 sixlegs only (see Plate X., Fig. 1), and creeps very slowly. 



