of larval organs is also of great importance for the phylogeny. The origin of repugnatoric 

 glands of Pentatomid-larvae has been proved as paired-form in embryos. These 

 conditions enable the determination of the phylogenetic relations among the families 

 and subfamilies of Pentatomids. 



DISCUSSION 



Sty s P. (Czechoslovakia). To support the hypothesis of Mrs. Polivanova on the original 

 presence of dorsal abdominal stink glands on all the urites of the nymphs of Heteroptera 

 I will mention the conditions existing in the family Dipsocoridae. This family — although 

 extremely specialized in some respects — has retained many very primitive characters 

 and is probably a direct descendant of the group from which both the develop- 

 mental lines (cimicomorphan and pentatomomorphan) of Geocorisae on the one hand 

 and the Amphibiocorisae on the other hand have developed (Stys in litt.). Many species 

 of Dipsocoridae possess in the nymphal stage 4 (some even 5) openings of dorsal abdo- 

 minal glands, often persisting in the adult stage. The fact that the last opening is 

 mostly without corresponding gland gives an evidence for the developmental trend 

 to the reduction of these organs. The presence of dorsal abdominal glands (or their 

 openings) even at 5 virites (more correctly in 5 intersegmentary regions) represents — as 

 far as we 1а10лу — the most generalized stage of evolution of these organs in postembryo- 

 nal stages of recent Hefero^^era and it clearly supports the hypothesis of Mrs. Polivanova. 



Mrs. Polivanova — on the basis of very convincing facts having been ascertained during 

 the study of embryogenesis of the superîamily Pentatofnoidea — is accepting the hypothe- 

 sis on the primitively paired arrangement of the dorsal abdominal glands in the nymphs 

 of Heteroptera. I must remark, however, that just in the family Dipsocoridae being — 

 as I have noted above — the most primitive family of Heteroptera as to the number 

 of dorsal abdominal glands, there exists a very evident trend to the doubling of primiti- 

 vely unpaired orifices of these glands accompanied with a retaining of the unpaired struc- 

 ture of the gland. It is well possible that the unpaired structure of these glands is a primi- 

 tive character and that we may see the beginnings of the trend to the doubling of them 

 in various arrangement of the sclerotized margins of orifices leading even to the doubling 

 of their ductus and perhaps stimulating the doubling of the proper gland during the phylo- 

 genesis. We cannot exclude the possibility that this doubling may appear in the highly 

 specialized group Pentatoinoidea as early as in embryonic stages. The solving of this 

 question will be possible only on the basis of comparative studies of embryogeny of dorsal 

 abdominal glands in all the groups of Heteroptera. 



<j Sympos. Evolutio lustctorum 81 



