AND THE LOWER ANIMALS. 83 



the head of the smallest pin, and the mother when lay- 

 ing them spreads over them little particles of dried-up 

 blood. From each of these eggs springs a diminutive 

 whitish larva, which soon assumes a brownish tint, and 

 carries a small tuft of filamentous hairs upon each 

 segment of its body. Although devoid both of legs 

 and eyes, this larva is not the less active on that 

 account , and is very well able to supply itself with 

 nutritious food. In the course of twelve or fifteen days 

 it has undergone its complete development. It then 

 spins a cocoon, composed of threads of very fine silk 

 closely interwoven, but which, being extremely transpa- 

 rent, allows us to watch the progress of the transforma- 

 tions which are going on within. As in the insects 

 before mentioned, the nymph is perfectly motionless, 

 and with the exception of the wings, exhibits all the 

 structures of the perfect creature, folded up, and, as it 

 were, shortened also. The adult flea can leap famously, 

 but he cannot fly. In this instance the metamorphosis 

 is incomplete, because of the non- development of the 

 organs of flight. 



Sometimes the arrest of development affects the 

 internal organs alone, leaving the outer essential 

 structures to be fully formed. In these cases, how- 

 ever, the metamorphosis is just as incomplete. 



It is in this way that naturalists account for the 

 peculiar characters of certain individuals which con- 

 stitute by far the greater portion of every insect 

 colony, and which, from the fact that they are neither 

 males nor females, have been called neuters. The 

 latter are really females, which have been modified by 

 the combined influence of an innutritious diet and 

 close confinement. As far as bees are concerned, this 



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