14 THE SHORTER SCIENTIFIC PAPERS 



appears inappropriate, for the reason that Audouin ('24) 

 first used it to indicate a supposed sclerite on the anterior 

 margin of the mesothoracic episterna in Dyfiscus circum- 

 flexus, the part in question being merely an articulative 

 process. Several years later, in a note to a translation of 

 a paper by MacLeay ('32), Audouin stated his belief that 

 the piece in the Hymenoptera termed squamula by Mac- 

 Leay was homologous to the parapteron which he himself 

 had described. This supposition was not only incorrect 

 but was subsequent to the terminology adopted by 

 Latreille. 



The value of the patagium on the prothorax has been 

 more or less discussed, but until we know more concerning 

 its development it is impossible fully to decide whether it 

 is equivalent to the wing, as suggested by Cholodkowsky 

 ('86), or to the pterygodum (tegula), the view adopted 

 by Haase ('86) and now so generally accepted. It should 

 be observed, nevertheless, that the reasons given by Haase 

 for reaching such a conclusion are far from adequate, 

 since the only evidence to which he called attention, other- 

 wise than a superficial resemblance, was that ( 1 ) chitinous 

 folds of a similar nature but of secondary origin are 

 present on the prothorax of certain Hymenoptera and 

 Diptera, while (2) the patagia do not exist during the 

 larval stage of the Lepidoptera, but commence their 

 development in the first few days of the chrysalid stage. 

 Unfortunately, however, Haase failed to demonstrate any 

 homologous structures in the Hymenoptera or Diptera, 

 and had he attempted to do so it is evident, from the pre- 

 ceding, that proof of their secondary nature would have 

 been difficult to establish. Moreover, the Anlage of a 

 structure must exist in potentio, and the time during the 

 post-embryonic stages at which it commences that which 

 is known as development can alone be of no particular 

 value in determining its palingenetic or cenogenetic char- 

 acter. The question as to whether the patagium rep- 

 resents a prothoracic pterygodum or a wing, must await 

 a large amount of comparative work based on embry- 



