A Study of the Protliorax of Butterflies. 



BY MAY H. \VELLMAN. 



The prothoiax, as it bears no wings and hence need not like the 

 meso- and metathorax, give space to a great muscular development, 

 is reduced to a narrow collar. The sclerites of the dorsum and 

 pleura are more or less fused, or some of them may be wanting 

 entirely; but the sclerites present may, usually without much diffi- 

 culty, be homologized with those of the more developed meso- and 

 meta-thoracic segments. Throughout the families of the Lepidoptera 

 the prolhoracic structure and development are, within certain limits, 

 uniform, but within those limits is found considerable variation with 

 respect to the development of certain sclerites, especially those of the 

 dorsum, where are found the prominent "prothoracic lobes" of 

 Scudder and the median chitenized sclerite homologous with the 

 scutellum of the other thoracic segments. 



The prothorax has much greater freedom of movement than the 

 other segments. This is due to the flexibility of the membrane 

 uniting it with the meso-thorax and with the head and which even 

 largely comprises the body wall of the segment. 



The membrane surrounds the strongly chitenized sclerites, except 

 where the niedian scutellum joins the narrow anterior and posterior 

 chitenized bands which articulate with the head and mesothorax. 

 All the parts of the pro- / 



thorax are closely beset yi^jL^ I 



Mm 



mm 



with scales varying in size ;,\ 

 and abundance in the 

 different groups. psc- 



The dorsal aspect of ^'^'" 

 the prothorax of Danais ' Wn/ 



archippus, fig. I, and a \ \ 



side view of Pier is rapce, ^^ j ^ jj 



fig. II, show all the parts of a typical prothorax. 



The "prothoracic lobes," the best known parts because the most 

 conspicuous, vary greatly in the different groups, from the thin 



(137) K.'^.N. UNH'. QUAE., VOL. III.. NO. 3, 1894. 



