METAMORPHOSES. 43 



tant resemblance to tlie quiescent pupss of these 

 animals."! 



I quite agree witli Miiller that the " complete meta- 

 morphosis " of such insects as the Lepicloptera is prob- 

 ably of more recent origin than the so-called " incom- 

 plete metamorphosis " of the Orthoptera and Hemip- 

 tera. 



Haeckel,^ like Miiller, attaches much importance to 

 the geological evidence as regards the sequence in 

 time of the dijfferent groups of Insecta; too much, 

 perhaps, if we consider the great imperfection of the 

 record, and the small number of fossil insects yet dis- 

 covered. For a long time, he sa^^-s, insects were 

 represented only by the four mandibulate orders — the 

 Archiptera, Neuroptera, Orthoptera, and Coleoptera — of 

 which the first is probably the common stock (Stamm- 

 form) of the three others. Subsequently the three 

 diverging series of suctorial insects — the licking, 

 piercing, and sucking — the Hymenoptera, Hemip- 

 tera, Diptera, and Lepidoptera, developed themselves 

 from the mandibulate series. He differs from Miiller 

 somewhat, however, in regarding, not the true Orthop- 

 tera, but the Pseudo-neuroptera, as most nearly re- 

 taining the type of the original insect stock. 



I confess that I feel great difficulty in understanding 

 by what natural process a suctorial mouth like that of 

 a gnat or butterfly could be developed from a power- 

 fully mandibulate type like that of the Orthoptera or 

 Coleoptera. At first the change would be a decided 

 disadvantage ; during the period of necessary quies- 

 cence the animal would be unable either to feed or to 

 defend itself. The extreme shortness of the life of 

 many insects in the perfect state seems also to present 

 an additional difficulty. 



The clue to the solution of this difficulty may, I 

 thmk, be found in the recognition of that distinction 

 between developmental and adaptive changes, to 



1 Miiller, loc. cit., p. 118. 



2 ' Natiirliche Scbopfungsgescliichte.' 



