ii FOOD OF INSECTS 61 



present in the butterfly, though in a very different 

 condition of form. 



This wonderful continuity of structure throughout 

 the lifetime of a butterfly, in its change from a 

 mandibulate* larva to a sucking perfect insect, shows 

 that the mouth-apparatus of every insect, of the 

 Haustellata and Mandibulata alike, is founded on the 

 one self-same plan. The best " all-round " or typical 

 development of the head and appendages is to be 

 found in mandibulates, as a whole in the beetle 

 family (Coleoptera). In Haustellata the deviation 

 from the type is enormous, but it consists merely in 

 the modifications of certain parts, which are more or 

 less developed in each order in accordance with the 

 general habits and instincts and modes of life. In 

 mandibulates in the carnivorous and omnivorous 

 families, whose habits require great strength, either 

 in obtaining food or in the construction of their 

 nests, the mandibles are the most important of the 

 oral organs and the most largely developed. In 

 Haustellata, whose food and modes of life are en- 

 tirely different, the mandibles lose their importance 

 and become atrophied, and their office, now altered 

 in its character, is performed by the maxillae and 

 labium. The development of these parts is so great 

 that they have become almost or entirely the sole 

 means of taking food, whereas in the higher forms 

 of insects it is only of secondary importance. 



The transformations of the structures of the 

 mouth of bees and flies are quite as wonderful. Into 

 these changes we must not enter. Of the three 

 kinds of insects, in fact of all insects without ex- 



