THE METATHORACIC PTERYGODA OF THE 



HEXAPODA AND THEIR RELATION 



TO THE WINGS'- 



On the anterior margin of the prothorax and meso- 

 thorax of the Lepidoptera are two small sclerites known 

 as the patagium and tegula, respectively; while in certain 

 other orders of Hexapoda (Hymenoptera, Neuroptera, 

 and Trichoptera) a small piece has been found at the base 

 of the mesothoracic wing which has been considered, 

 equivalent to the tegula. Further than a few suggestions 

 based on limited observations, no attempt has been made 

 either to ascertain the value of these pieces or to demon- 

 strate the existence of similar homodynamous or homolo- 

 gous structures in the hexapods. 



The purpose of the present paper is to call attention 

 briefly to the general presence of a sclerite on the hexapod 

 metathorax which seems homodynamous with the so- 

 called tegula, to make some suggestions concerning termi- 

 nology, and especially to point out that the present view 

 concerning the metamerism of the antennate arthropods 

 appears worthy of reconsideration. 



The relation of the tegula, or pterygodum as I prefer 

 to term it, to the pieces of the mesothorax, which is in 

 many respects the most generalized of the three thoracic 

 segments in the insects, is shown in Fig. 1. Bearing in 

 mind now that the mesothorax and metathorax are equiv- 

 alent, the various components of each being reduplicated 

 in the other segments, subject, however, to the factors 

 governing the specialization of the different groups of 

 insects, the existence of a corresponding piece in the meta- 

 thorax would a priori be inferred. The presence of such 

 a piece^ is represented in the accompanying diagram, 



■"^From comparisons made throughout the Hexapoda it is evident that this does not 

 correspond to the more or less chitinized part of the epimeron at the base of the 

 wing in most Lepidoptera. 



^Reprinted from The American Naturalist, vol. 35, no. 413 (1901), pp. 357-362. 



