24 



opinions can be true for different objects. In the literature I found 

 some papers which specially treat this question. It is a pity 

 that the last-mentioned writer Kummeth, apparently was not 

 acquainted with Boas' paper. 



Boas devotes p. 390 of his article (1899) to the question of the 

 thoracic stigmata. Relying on his examinations of Cossus ligni- 

 perda and Ergates faher (a Cervicornid) he says that there are 

 two thoracal stigmata. The first is shifted to the prothorax, the 

 second forms a closed, rudimentary stigma in the intersegmental 

 membrane between the mesothorax and the metathorax. This rudi- 

 mentary stigma is situated lower than the ordinary ones. The so-called 

 rudimentary stigmata, lying in the stigmal line, are in reality the 

 origins of wings. In the imago the closed larval stigma becomes open. 



Tower (1906) found in Leptitiotarsa „that the wing in develop- 

 ment starts from a minute invagination of cells in the region of 

 the wing spots, which is an area, as shown by Verson, myself 

 and others, homologous to the spiracular centre of other segments 

 (I.e. p. 163)." 



G. C. Crampton (1914) does not enter into this question. He is 

 unwilling to accept the assumption of subsegments in the thorax, 

 since he is convinced that all theories about the compound-segment 

 are unfounded (p. 56). 



Janet (1909) gives a very interesting list of the origin of the 

 different segments and subsegments. 



From this I only quote: (see also Chapter IV, p. 27). 



Ordre Ordre 



ontogenique. anaturaique. 



spir. prothorac. des Diptera. 

 spir. mesothoracique. 

 spir. metathoracique. 



We therefore see that Boas and Janet agree with Henneguy 

 in the supposition that the prothorax has no stigma of its own 

 and that a shifting of the stigma in an oral direction has taken 

 place when a prothoracal stigma occurs. 



