(^^ AND ^^^ 



JOURNAL OF VARIATION. 



No. 4. Vol. V. April ISth, 1894. 



1'lie Life-jJistory of a Lepidopterous Iiisect, 



Comprising some account of its Morphology and Physiology. 

 By J. W. TUTT, F.E.S. 



(Coutinned from page 68). 



Chap. I. 

 CLASSIFICATION. 



4. On the kelationship which exists between the 

 SEVERAL Orders cojiposing the Class Insecta. — Oue of the most 

 recent attempts to show cliagTammatically the evolutionary relations of 

 the various Orders of insects to each other, is that made by A. Hyatt 

 and J. M. Arms (Guides to Science Teaching, No. viii.) and reprinted in 

 Fsyche, vol. vi., pp. 12-13, diag. 1, 2, 3. Tliese authors conclude 

 that, of the higher (winged) forms which may be assumed to have 

 arisen from a common stem, the Neuroptera, Mecoptera and Trielioptera 

 may be considered as forming a sub-group, passing off from the common 

 stem in different directions ; the Lepidoptera, Hymeno2)tera and Diptera, 

 as forming another radiating off in other directions, whilst tlie Coleoptera 

 have no relations to the others save through the purely imaginary 

 ancestral l)ase. Estimating approximately the degree of specialization 

 attained by the adults (imagines) and taking it as the basis of their con- 

 elusions, these authors consider tlie Diptera, Hymenoj^tera, Coleoptera 

 and Lepidoptera, to be the highest in the scale of evolution, their 

 relative order being as here set down. The relationshiji of existin"- 

 larval forms to a primitive type and to each other is fully discussed, as 

 well as the moditications Avhich particular groujis have undergone in 

 their relationship to the primitive type {Psyche, vol. vi., pp. 37, 44). 



It is, of course, absolutely necessary, that in using the terms hio-her 

 a,nd lower, we consider as the highest grou}) that which has under- 

 gone the greatest degree of specialisation from the ancestral type, and 

 then, undoubtedly the clioice lies between the Hymenoptera and Diptera. 

 Lowne says : — "The Diptera are far more remarkable in tlieir dcveloi)- 

 ment history, and in the modification of structure wliicli they present 

 in the adult or imago form. In this relation, the strong tendency of 

 many to produce their young alive, and the fact that some have a 



