The presence of the rDNA-positive C-positive regions underlines two surprising points: the formation and maintenance of this region itself, and its presence in metaphases of five distantly related taxa, i.e., the five species studied here, and two species in Leptynia . Previously, large telomeric regions enriched for rDNA and telomeric repeats were discovered in voles, i.e., Sorex granarius . These regions contain more than 300 kb of discontinued telomeric repeats, localized on short arms of acrocentric chromosomes. In some telomeric regions, the sets of telomeric repeats alternate with repeats of rDNA and other DNA sequences. In the termini of other chromosomes, the sets of telomeric repeats were located a little further away from the clusters of rDNA . The possible mechanisms of formation of these terminal regions include unequal crossing-over and amplification of these repetitive DNA arrays . These very large telomeres were detected only in one vole species, Sorex granarius. In a closely related species, Sorex araneus, the telomeres were of conventional size . The large C-positive regions in stick insects showed some analogy and at the same time differences from the large Sorex granarius telomeres. Like Sorex granarius telomeres, they contain regions enriched for rDNA or both rDNA and telomeric repeats. Furthermore, in S. inexpectata this region is enriched by telomeric repeats to a smaller extent. It is unknown if the arrays of (TTAGG)n repeats in this species are shorter or their number was decreased. These regions were found both in parthenogenetic females (Figure 1, Figure 2, Figure 3, Figure 4 and Figure 5) and in bisexual species (Figure 6) . For stick insects, we can suggest mechanisms involved in the formation of these large C-positive regions, like unequal crossing over, or DNA amplification in somatic cells, as is involved in the formation of a homogeneously staining region .