lOi SURVEY OF THE REPRODUCTIVE PROCESS 



egg, is first converted into a footless worm, resembling the 

 higher Entozoa, or the inferior Annelida, in its general or- 

 ganization, but possessing the number of segments thirteen 

 which is typical of the class of Insects."* It is at this 

 stage of its progress that the embryo of the Diptera, Hy- 

 menoptera, and of some of the Coleoptera or Beetle-tribe, 

 comes forth as a larva, such as is commonly known as a 

 " Maggot." In Butterflies, again, and in the greater num- 

 ber of Beetles, the organization of the larva is rather more 

 advanced, as it is furnished with the rudiments of the 

 thoracic legs, besides certain provisional organs of the same 

 nature on the posterior segments of the body the abdomi- 

 nal tubercles or pro-legs. Such larvse are termed " Cater- 

 pillars." In the Orthoptera, Hemiptera, and a portion 

 of the Coleoptera, there cannot be said to be any pro- 

 per larvae, as the young do not emerge from the egg 

 till they have attained the conformation of the adult in 

 almost all respects, except the evolution of the wings. The 

 true or vermiform larva feeds voraciously, and continues 

 for some time without any other obvious change than a 

 rapid increase in size, attended generally with several cast- 

 ings of its skin. As the period of its transformation ap- 

 proaches, it passes into the pupa condition a state of inac- 

 tivity, during which it undergoes its change into the imago, 

 or perfect insect, with six jointed legs, four wings, and other 

 peculiarities of that type of organization. " The pupa is 

 enclosed in the last skin exuviated by the larva, which, in- 

 stead of being thrown off, dries up, and remains to encase 

 the proper skin of the pupa that is formed beneath it ; and, 

 in addition to this, it is frequently protected by a silken 

 ' cocoon,' the construction of which was the last act of 

 larval life."")- To this association of external inactivity, 

 with great internal constructive energy that is, to the 



* Carpenter, Compar. Physiol., 4th Ed., p. 599. 

 t Carpenter, Op. Cit., p. 601. 



