450 TRANSFORMATIONS OF INSECTS. 



the Zoe'a, which succeeds. Like the larvae of those spiders which 

 undergo metamorphosis they have six legs — the three pairs of 

 extremities which characterise the true insects as a class. More- 

 over, the mouthpieces of the immature representatives of the 

 different classes are of the same number. Fritz Muller points this 

 out with great force, when arguing respecting the interesting 

 question of the origin of the classes included under the A rticidata 

 from a common ancestry, and remarks, moreover, that the true 

 insects, like the Zoece of Crustacea have no appendages to the 

 abdomen, and that both have mandibles without palpi. When the 

 habits, transformations, and structures of the water insects are 

 considered, and especially those of the wonderful water larvae of 

 the Hydrocampa moth and the Ephemera larva, there is no diffi- 

 culty in believing in the descent of the more complicated terres- 

 trial forms of insects from the Naicplii or Zocce of early fresh 

 water Crustacea. 



Fritz Muller has pointed out that the OrtJwptcra with larvae 

 which have eleven segments in the abdomen (and not nine 

 as in the Lepidoptera larvae) agree with the rudimentary prawns 

 — the ZoccB, and with the higher Crustacea, in the number 

 of their body segments. He notices, moreover, that in the 

 Orthoptera and the Crustacea the o.^'g orifice and the vent 

 are placed on different segments, and not on one particular 

 ring. 



The oldest known insects are Orthoptera, or the closely allied 

 Neuroptera and Coleoptera. It is, therefore, important to remember 

 that the majority of the Orthoptera leave the egg not in a more 

 or less embryonic condition, but as larvae which resemble greatly 

 and have the same habits as the adult forms. The development of 

 wings proceeds, and the generative processes are adopted, and that 

 is nearly all that takes place between birth and adult age, except 

 simple growth. The growth progresses without distinct states, 

 and is accompanied by no marked phases of transformation. All 

 this hints at the complete metamorphosis of other insects being 

 an acquired gift during the struggle for existence ; and when 

 the structural relations between the Orthoptera and the Zoeez of 

 the Crustacea are considered, the origin of the two articulate or 

 insect forms from some older kind of Crustacea commends itself to 



