I. TRÄGARDH, LEPIDOPTEROUS LEAF-MINERS. 5 



looked like; subsequently I found the more full-grown larvae 

 in the folded or rolled leaves, and finally, on examining many 

 blotch mines, I was able to follow the whole transformation 

 of the »flattened type», to use Chambers' terms, into the 

 cylindrical type. 



This discovery, which was made without my having access 

 to the litterature referring to this subject, greatly aroused 

 my interest and since that time I have during my leisure- 

 hours endeavoured to collect more material on leaf-miners, 

 chiefly microlepidopterous, but also amongst the coleoptera, 

 diptera and the hymenoptera. Some papers referring to these 

 have already been published [15, 16, 17], but the main portion 

 of the studies is as yet unpublished, owing, amongst otber 

 things, to the fact that I have failed to find representatives 

 of some genera. In spite of this deplorable circumstance, 

 which is due to the impossibility to find the time necessary 

 for the extensive excursions indispensable for bringing together 

 a large amount of material, I do not hesitate to publish here, 

 in a condensed form, some results of my comparative-morpho- 

 logical studies on the leaf-mining lepidopterous larvae. 



The purpose of this paper is to show, how, by examing 

 the larvae of different genera, we are able to trace the gradual 

 modification which has taken place in the shape of their 

 mouth-parts, and finally resulted in a head so singularly 

 specialized as that of the first instar of a Gracilaria or of 

 a Phyllocnistis-\diTV3i. It is obvious, that this comparative 

 method is the only way to enable us to find the true ho- 

 mologies of the specialized mouth-parts. 



The material on which this study has been made has 

 been collected by the author in Båstad, County of Halland, 

 June— 15 July, 1909; South-Fyn, Denmark 20 July— 30 August, 

 1909 and 10—20 Oct., 1912; and in the neighbourhood of 

 Stockholm, in 1910, 1911 and 1912. 



It consists of representatives of the following genera: 

 Eriocrania, Cemiostoma, Lyonetia, Phyllocnistis, Elachista, 

 Nepticula, Tischeria, Ornix, Lithocolletis and Gracilaria. 



2. Relation of structure and habits. 



A pronounced dimorphism in the mouth-parts of the 

 younger and the låter instars is as yet only found in some 





