34 2 ANIMAL DEFENCES 



perfectly, the shape of the armour-covered head and tail enabling- 

 them to be snugly tucked away side by side. In the following 

 passage Darwin (in A Naturalist's Voyage) speaks of it thus: 

 ''It has the power of rolling itself into a perfect sphere, like one 

 kind of English wood-louse. In this state it is safe from the attack 

 of dogs ; for the dog, not being able to take the whole in its mouth, 

 tries to bite one side, and the ball slips away. The smooth, hard 

 covering of the mataco offers a better defence than the sharp 

 spines of the hedgehog." The scaly Pangolins of South Africa 

 and South- East Asia practise the same tactics. Both the Com- 

 mon Porcupine (Hystrix cristatus) and the Common Hedgehog 

 (Erinaceus Europczus] roll themselves up when threatened by 

 enemies, the quills or spines being at the same time erected. 



Among Primitive Molluscs the curious Mail-Shells (Chiton, 

 &c.) are defenceless below, but are provided with eight protec- 

 tive plates above. These overlap in such a way as to form a 

 complete investment when the animal rolls up, as it is in the 

 habit of doing when alarmed. Two Arthropod examples will 

 serve to further illustrate the same method of defence. One is 

 that of the long since extinct Trilobites, rolled-up specimens of 

 which are frequently found in the fossil condition. Some members 

 of the group of land-crustaceans, popularly known as Wood- Lice, 

 have earned the name of " Pill Bugs " from the fact that they 

 practise this mode of defence, a common British species, the Pill 

 Wood- Louse (Armadillidium vulgare}, being a good illustration. 



We now pass on to the consideration of habits not related to 

 the effective use of defensive armour. 



DEATH -FEIGNING HABIT. Many carnivorous animals which 

 pursue living prey will not condescend to touch dead bodies, and 

 hence the fact that a number of forms, when suddenly attacked or 

 hard pressed by their foes, pass into a state of " apparent death ", 

 may perhaps be explained as a defensive arrangement. Various 

 views have been held regarding this phenomenon. Some believe 

 it to be a deliberate action, an actual "feigning" of death, others 

 suppose it to be a kind of paralysis induced by fright, while the 

 suggestion has also been made that it is comparable to a state 

 of trance or catalepsy induced by hypnotic (mesmeric) influence. 

 It is not likely that the same explanation will apply in all cases, 

 and the heading of this section is adopted solely for convenience, 

 and does not express belief in the first way of explanation. 



