MITES AS DECADENT SPIDERS 



295 



specialised, yet are more, not less, capable in consequence. 

 But they are at a perilous point of perfection. In the 

 animal series, as in the history of art, decadence often 

 follows suddenly upon periods of the highest attainment, 

 and in virtue of the same law of development. From the 

 spiders have arisen small spider-like creatures the mites 

 and tics which no longer " trap " or hunt their prey, but 

 have learnt to attach themselves to the bodies of larger 



FIG. 41. Development of the barnacle from a free-swimming stage 

 with six active legs. The larva of Balanus and of Chthamalus, 

 closely allied to the true Lepas barnacle, are drawn since they do 

 not differ from that of Lepas. In the drawing labelled " pupa " the 

 head with its two feelers outspread is seen fixing the young animal 

 by a cement, which it secretes, to a piece of wood. 



animals and plants and to feed on their abundant juices. 

 Some have gone further and feed on hair, skin, and 

 feathers, or even on the powdery masses of dead vege- 

 tables, and whilst retaining the general shape of spiders 

 have lost the extraordinary agility, the keen sight and 



