41] LEPIDOPTEROUS LARVAE — FRACKER 41 



PART TWO. SYSTEMATIC OUTLINE OF 

 FAMILIES AND GENERA. 



A complete history of the study of caterpillars would begin with 

 work done centuries ago and would include the names of many 

 scientists. It would necessarily embrace all discussions of larvae of the 

 Lepidoptera. There is now in manuscript a list, as nearly complete as 

 such a list can be made, of all published papers containing descriptions 

 of immature stages of American members of this order, but its size is so 

 great that arrangements for its publication are difficult. Nevertheless, 

 no object would be served here by an extended historical account, espe- 

 cially as the results obtained by the older workers were not of such a 

 nature as to aid materially in the preparation of this paper. 



The period from Aristotle to the last quarter of the nineteenth cen- 

 tury is discussed at some length in the introduction to "Die Schmetter- 

 linge Europas," the third edition, edited by Arnold Spuler. Since that 

 time the subject has been put on a more scientific basis by the work of 

 two men. Dr. Harrison G. Dyar, in addition to the papers mentioned 

 in Part One, has written excellent descriptions of new larvae for various 

 publications every year for a quarter of a century. These are undoubt- 

 edly the best descriptions of larval Macroheterocera extant, for they give 

 not only color but the structural characters which indicate their family 

 and sometimes their generic position. Since 1905 several papers have 

 been published by Dr. W. T. M. Forbes, who has made a detailed study 

 of the head sclerites, mouth parts, and prolegs of a large number of 

 species. Representatives of all the more important families of Macro- 

 lepidoptera have been described and figured. The observations of Dyar 

 and Forbes mark the first advance stride toward an accurate knowledge 

 of the structure and relationships of the larvae of this order. 



In spite of the work of these investigators certain gaps remain in 

 our knowledge, especially of those species of importance to economic 

 entomologists. The most conspicuous of these is our ignorance of the 

 structure and taxonomic characters of the larvae of the Microlepidop- 

 tera. It is true, as one author puts it, that "there seems to be little 



