273 



(Nahublattella, Eiiphyllodromia, Supella) and Blaberidae (Nauphoeta, Byrsotria, Blaptica, 

 Blabenis) it is thus evident that the phallomere complex has undergone a change of its 

 left-right-asymmetry (like a mirror-image): This hypothesis first proposed by Bohn (1987) 

 is strongly supported, and many new arguments are now available. According to e.g. Bohn 

 (1987), the phallomere complex of most species of Ectobius (Ectobiinae) is normally 

 orientated, but some species show the same orientation as Blaberidae. The latter species, 

 as compared with the former, clearly show that a reversal of the left-right-asymmetry must 

 be regarded as a possible evolutionary pathway. 



Vestiges of a bilateral symmetry or side-homologies within the phallomere complex are 

 revealed in only very few respects: (1) The primary phallomero-sternal muscles si and s2 

 are assumed to be side-homologous (e.g. fig. 37), and side-homology might also be 

 assumed for the areas of their dorsal insertions. In the primitive case (compare in 6.9.) 

 these are the anterior L41-region on the left side and the anterior margin of R3 on the 

 right side. These two areas have additionally in common that the margin of the 

 sclerotisation is more or less groove- or beam-like (apodemes swe or age). (2) The 

 transverse phallomere muscles (b-muscles) might be assumed to have primitively a 

 symmetrical course, and their left and right insertion areas might be side-homologous. The 

 situation in Mantoida might be interpreted in this way: The insertions of muscle bl (fig.43) 

 are next to those of the side-homologous s3 (left side) and s4 (right side), and the resulting 

 side-homology would again concern the (median) anterior margins of R3 and L4. (3) The 

 dorsal transverse muscles b4a and b4b (fig.48, 58, 109) have their right insertions close 

 to each other, but the left insertions are quite distant from each other. From their course 

 it can be at most deduced that there is some kind of side-homology between the 

 dorsomedian parts of the left complex and of the right phallomere. As regards the re- 

 maining parts of the right phallomere and of the left complex, there are in no species any 

 similarities in the positions, in the special shapes, or in the muscular connections of 

 elements which show similar spatial interrelationships on both sides. Hence, no further 

 side-homologies can be reliably assumed. 



The primary phallic lobes of nymphal Blattaria and Mantodea are certainly homologous 

 with those of the other Ectognatha (in a more or less strict sense). In most other Ectognatha 

 (also in the most primitive: Archaeognatha, Zygentoma) the external genitalia developing 

 from these phallic lobes are bilaterally symmetrical. Hence, the male external genitalia 

 have certainly been bilaterally symmetrical in some early members of the common stem- 

 group of Blattaria and Mantodea. However, from this it cannot be concluded that there 

 must be extensive vestiges of this bilateral symmetry in the sclerotisations, in the formative 

 elements, or in the musculature of the phallomere complex of the extant species (or of 

 the later members of the common stem-group): The sclerotisations, muscles, and formative 

 elements present in the common ground-plan of Blattaria and Mantodea (or more or less 

 extensive parts of them) might have evolved later - at a time when the extreme asymmetry 

 had already established. Nothing is known about homology relations between these 

 Dictyopteran phallomere elements and the elements of the male genitalia in other insect 

 groups, and hence there is no information about which elements have already been present 

 when the Dictyoptera branched off from their (unknown; Kristensen 1995) sister-group. 



