226 ROMANCE OF THE INSECT WORLD CHAP. 



Beautiful examples of Alluring Colouring occur in 

 the resemblance of Mantidae to the excreta of birds. 

 Flies are often attracted by such droppings, and the 

 Mantidae take advantage of this fact to secure their 

 prey. A similar instance was discovered by Mr. 

 Forbes in Java, in a spider (Ornithoscatoides 

 decipiens), whose imitation of a bird's dropping 

 from a height on a leaf is carried out with minute 

 detail colouring, form, and habits contributing to 

 the success of the resemblance (see Fig. 43). This 

 is one of the most remarkable instances of faithful 

 assimilation of an animal to a vegetative or inanimate 

 object, and affords a wonderful example of what is 

 in the power of natural selection to accomplish. The 

 principle of natural selection alone is sufficient to 

 explain the case, for the acquisition of every new 

 grade in the likeness would at once give the owner 

 an advantage in the continual struggle for food. 



In the foregoing cases of protective resemblance 

 the imitated objects are constant in their nature, and 

 the disguising characters of the imitating species 

 remain constant throughout the lifetime of each 

 individual. As regards leaf-butterflies and others 

 which resemble withered leaves, the constancy of the 

 individual is no less perfect, but the imitated objects 

 vary slightly in hues, calling forth a corresponding 

 variability of colour among the copying species. 

 There are a few examples where each insect under- 

 goes a rapid change of colour once during its lifetime. 

 It acquires a new habit, entailing change of environ- 

 ment, and with the fresh surroundings relationship 

 must be set up. Obviously this change of habit in 



