204 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 1 37 



tion of some of the fundamental problems of adaptation and trans- 

 form! sm. For this reason I have for years been led to investigate 

 such a rich field and consequently have discovered a series of facts 

 which I think will be useful in the elucidation of the controversial 

 subject. 



I have studied larvae and adults of several species of holometabolic 

 and hypermetabolic insects belonging to various families of the Lepi- 

 doptera, Coleoptera, and Hymenoptera. I shall arrange my observa- 

 tions in groups according to the taxonomic order, dealing first with 

 preimaginal stages. Facts, suitably coordinated, will support my 

 affirmations, and useless discussions will be eliminated. Finally, the 

 general conclusions reached by me will be presented, summed up in 

 18 distinct units. 



I. LARVAE OF LEPIDOPTERA (ERIOCRANIIDAE, NEPTICULIDAE, 

 TISCHERIIDAE, GRACILARIIDAE) 



The larvae of Lepidoptera which pass a part or the whole of their 

 postembryonic development within leaves (as miners) are very nu- 

 merous. There are some which develop and pupate within their mines, 

 some which develop within the mines but pupate outside, and others 

 which begin their development endophytically and end it ectophytically. 

 A larva, when it is forced to move in the body of a vegetal tissue, 

 goes about overcoming the resistance of the medium or utilizing it. 

 To overcome it, the most expeditious way is that of eating the tissue. 

 For making use of this resistance, if the mine is low and narrow, it 

 is most suitable to set the head capsule at prognathism, reduce thoracic 

 and abdominal limbs to simple protuberances or replace them with 

 "ambulacral areolae," make somites jutting sidewise, etc. Well, we 

 shall see how most of the changes undergone by the larvae of leaf- 

 mining Lepidoptera are actually related to the various methods of 

 taking food and ways of boring mines. 



Indeed if we take into account some Homoneura and Heteroneura 

 Monothrysia such as Allochapmania Strand, Nepticula Zell., and 

 Tischeria Zell., which bore intraepidermic or subepidermic mines in 

 the leaves, pupating in the same place (inside or outside the mine) 

 or in the ground, we see that their larvae perform their whole de- 

 velopment in the leaves of the host plant, but do not change their 

 form radically during the development (a true and simple holome- 

 tabolism or euholometabolism). They exhibit a more or less flattened 

 body, prognathous head capsule caudad continued by two large dorsal 

 plates invaginating within the thorax and strengthened by rather 



