CHAP. IV Shifts for a Living 63 



parts of the body, and particularly long plume-like pieces 

 are fixed on the hea:d." Thus, as Carus Sterne says, is the 

 story of " Birnam's walking wood " re-enacted on the sea- 

 shore. Furthermore, a Stenorhynchus which has been 

 cleaned will immediately begin to clothe itself again, with 

 the same care and precision as before. Mr. Robertson of 

 Millport often saw Stenorhynchus longirostris — a common 

 crab — picking about its limbs and conveying the produce 

 to its mouth. " If other observations confirm the view that 

 this animal is a true vegetarian, we shall have one example 

 at least of an independent agriculturist, who is not only 

 superior of his lands, but carries them with him when 

 he removes." I also have seen the crab doing what " the 

 naturalist of Cumbrae " observed. In further illustration 

 of masking we may cite Dromia vulgaris, often covered 

 with sponge ; Dromia excavata, with compound ascidians ; 

 the Amphipod Atylus, with seaweed ; while a species of 

 Dorippe is said to bear a bivalve shell, or even a leaf, as a 

 shield, and another crab cuts off the tunic of a sea-squirt 

 and hitches it on his own shoulders. 



Sometimes this masking serves as a warning or deterrent ; 

 witness that hermit-drab {Pagurus cuanensis) whose • stolen 

 shell is surrounded by a bright orange sponge (Suberites 

 domunculd). As this sponge is full of flinty needles, has a 

 strong odour and a disagreeable taste, we do not wonder 

 that Mr. Garstang finds .that fish dislike it intensely, nor 

 can we doubt that the hermit-crab trades on the reputation of 

 its associate. In other cases the masking will aid in con- 

 cealment and favour attack. To the associations of crabs 

 and sea-anemones we shall afterwards refer. 



II. Combination of Advantageous Qualities. — Mr. 

 Poulton describes, in illustration of the combination of 

 many methods of defence, the case of the larva of the 

 puss moth {Cerura vinuld). It resembles the leaves of the 

 poplar and willow on which it lives. When disturbed it 

 assumes a terrifying attitude, mimetic of a Vertebrate 

 appearance ! The effect is heightened by the protrusion of 

 two pink whips from the terminal prongs of the body, and 

 finally the creature defends itself by squirting formic acid. 



