64 The Stitdy of Animal Life PART i 



Yet in spite of all this power of defence, the larva often falls 

 a victim to ichneumon-flies. These manage to lay their eggs 



within the caterpillar, which 

 by and by succumbs to the 

 voracity of the hatched 

 ichneumon maggots. Mr. 

 Poulton believes that the 

 puss moth larva " has been 

 saved from extermination 

 by the repeated acquisition 

 of new defensive measures. 

 But any improvement in 

 FIG. 13. "Terrifying attitude" of the the means of defence has 



caterpillar of Cerura vinula. (From ^ PPr , m^f- K v 4-V, P crrpntpr 

 Chambers's Encyclop. ; after Poulton.) ' 1Gl T 



ingenuity or boldness of 



foes ; and so it has come about that many of the best- 

 protected larvae are often those which die in the largest 

 numbers from the attacks of enemies. The exceptional 

 standard of defence has been only reached through the 

 pressure of an exceptional need." 



1 2. Surrender of Parts. Among the strange life - pre- 

 serving powers which animals exhibit, we must also 

 include that of surrendering parts of the body in the 

 panic of capture or in the struggle to escape. A rat 

 will gnaw offra leg to free itself from a trap, and I have 

 heard of a stoat which did not refrain from amputating 

 more than one limb. But the cases to which we now refer 

 are not deliberate amputations, but reflex and unconscious 

 surrenders. Many lizards (such as our British " slowworm ") 

 will readily leave their tails in their captor's grasp ; crus- 

 taceans, insects, and spiders part with their limbs and 

 scramble off maimed but safe ; starfishes, brittle-stars, and 

 feather-stars resign their arms, and the sea-cucumbers their 

 viscera. A large number of cases have been studied by 

 Fredericq and Giard. 



Among Crustacea the habit is most perfectly developed 

 in the crabs, e.g. the common shore-crab (Carcinits incenas), 

 and in the spiny lobster {Palinurus\ but it is also exhibited 

 by the crayfish (Astacus\ the common lobster (Homan/s), 



