A STRUCTURAL STUDY OF SOME CATERPILLARS.* 



By William T. M. Forbks, 

 Clark University, Worcester, Mass. 



Although the Lepidoptcra have been studied for a long time 

 little attention has been paid as yet to the minute descrip- 

 tion of their caterpillars. In describing a caterpillar most 

 authors have contented themselves with the colors and markings, 

 adding an occasional note on the structure if especially striking. 



My problem, therefore, has been to discover external struc- 

 tures characteristic of the groups of caterpillars, especially such 

 as have been less carefully studied by others. This paper then 

 deals mainly with the parts and setae of the head. I have also 

 summarized my studies on the prolegs, and have included some 

 of Dyar's characters derived from the body-setae. I have tried 

 so far as possible, to lay emphasis also on such characters as could 

 be determined from the cast skin. It appears that, with a little 

 care since they are brittle, the characters of the head can be made 

 out quite as easily from cast skins as from killed material. The 

 body can not be studied quite so well, but at least the arrange- 

 ment of the proleg hooks, and also the type of vestiture, whether 

 primary, secondary or tufted, can be made out without trouble. 



Material and Methods. 



My material is made up of specimens rej^resenting about 125 

 genera, preserved in various ways. The major part were col- 

 lected personally in the course of the past summer and preserved 

 in alcohol. There were also a few cast skins, and a few caterpil- 

 lars dried whole without any preparation. To this I added a num- 

 ber of species from the American Entomological Company, which 

 were preserved in formalin, and a series of inflations, mostly of 

 Microlcpidoptera, from Staudinger and Bang-Haas. 



Most of my alcoholic material was cleared by boiling in 10 per 

 cent, caustic soda, cutting the skin down one side, and separating 

 the maxillae and labium from the rest of the head. The dried 

 caterpillars were treated in the same way. Often one mandible 

 was also removed to give a clearer view of the labrum. The 

 prepared skins were then preserved in alcohol, except a few that 



* a Dissertation submitted to the Faculty nf Clark University, Worcester, Mass., in partial 

 fulfillment of the refiuirements for the degree of Doctor of Philosophy, and accepted on the recom- 

 mendation of C. F. Hoclge. 



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