224 Annals Entomological Society of America [Vol. XI, 



Third, complete metamorphosis or homometabolous develop- 

 ment. This is characteristic of the Diptera, Lepidoptera, et al. 



The features of the cenogenetic development of insects with 

 an incomplete metamorphosis, as the term is now restricted, are 

 very different from those of the cenogenetic development of 

 insects with a complete metamorphosis. In insects with an 

 incomplete metamorphosis the immature stages are modified so 

 as to fit them for aquatic life; the more striking features of 

 larvae, the elongate form of the body, the internal development 

 of wings, and the retarding of the development of the compound 

 eyes are not exhibited by them. 



From this it can be seen that the immature stages of the 

 Plecoptera, the Odonata, and the Ephemerida differ funda- 

 mentally from those of insects with a gradual metamorphosis 

 on the one hand and from those of insects with a complete 

 metamorphosis on the other; and that the reasons that make 

 desirable the restriction of the use of the term larva to designate 

 the young of insects with a complete metamorphosis make 

 desirable a distinctive term for the sidewise developed young of 

 those with an incomplete metamorphosis. 



I, therefore, propose the restriction of the term nymph to 

 the designating of the early stages of insects with a gradual 

 metamorphosis and the use of the term naiad for designating 

 the immature stages of the Plecoptera, Odonata, and 

 Ephemerida. 



If this proposal is adopted the three terms, nymph, naiad, 

 and larva will each indicate a distinct type of immature insect ; 

 and their use will tend to emphasize the distinctive character- 

 istics of the three types of metamorphosis. 



