326 



- Though the demarcation or identification of a ground-plan subregion has a clear 

 theoretical background (indivisible unit = 1 sclerite), no uniform principle can be 

 recognised in the practical application to extant species (analysis of Blattinae), let alone 

 the attempt to come close to the definition or to explain discrepancies. It is not 

 comprehensible why Mizukubo & Hirashima assume for some sclerites of Blattinae a 

 contribution of several subregions and why for other sclerites they do not. The dividing 

 procedure seems to aim to have subregions with coiTesponding relative positions on the 

 left and on the right side. So the division of the L41-region (into LD21 and LD3) results 

 in having - hke on the right side (RD21 and RD3) - one subregion for the sclerotisation 

 in the anterior ventral wall (LD3 and RD3) and one for the sclerotisation in the lateral 

 edge of the phallomere (LD21 and RD21). (According to my results, only the division 

 on the right side is a ground-plan feature: articulation A3.) 



The argumentation concerning homology assumptions 



Mizukubo & Hirashima mainly make use of the first criterion of homology (relative 

 positions). However, the specific procedure of the dividing into subregions described above 

 makes the homology assumptions questionable: From the fact that the left as well as the 

 right side can be (in a largely arbitrary way) divided into 1 1 areas having the same relative 

 positions cannot be decuced that these areas are side-homologous because of their equal 

 relative positions (circular argumentation). Assumptions of homology would only be 

 justified, if (1) these areas have specific features in common (i.e. if there are similar 

 structures in the same relative positions, e.g. similar sclerites, muscle insertions, 

 processes, apodemes, etc.), or if (2) an equal arrangement on both sides results from a 

 uniform principle of dividing. The same critique applies to the homology assumptions that 

 concern the comparison of different species: Again, the surface of the phallomeres is 

 divided largely arbitrarily into subregions with equal relative positions, and the subregions 

 are then supposed to be homologous because their relative positions are equal. 

 Moreover, the reliability of the homology hypothesis becomes further diminished by the 

 fact that neither the side-homologies nor the homologies between different species are 

 supported by similarities in the arrangement of the musculature or in the intensities of the 

 mutual relations between the subregions / sclerites: 



- Side-homologies: Related to the side-homologies assumed by Mizukubo & Hirashima, 

 the musculature of Periplaneta is completely different in the left and in the right half 

 of the phallomere complex (of 20 phallomere muscles only two are a pair, Mizukubo & 

 Hirashima, fig.6). As regards the principal relative positions of the subregions, the 

 association patterns of the left and of the right side of Periplaneta are very similar. This 

 simply results from the fact that the two halves of the phallomere complex have been 

 arbitrarily divided into subregions which are in the same relative positions. However, 

 the subregions of the left and of the right side supposed to be homologous hardly have 

 any intensity of the mutual relations in common (Mizukubo & Hirashima, fig.2). 



- Homologies between species: In Periplaneta and Blattella germanica, of 14 or 7, 

 respectively, intrinsic muscles of the left half of the phallomere complex only 2 have 



