Chromosome mapping in (De Geer, 1773) (Orthoptera) from the Iguaçu National Park - Foz do Iguaçu, Paraná, Brazil.

In this paper, we present the cytomolecular analysis of a population of collected in the largest fragment of the Brazilian Atlantic forest, the Iguaçu National Park. The diploid number in males was 23 (22+X0), with two large pairs (1-2), 7 medium (3-9), 2 small (10-11) and the X chromosome of medium size. Heterochromatic blocks were evident in the pericentromeric regions of all chromosomes. Heterogeneity in the distribution of heterochromatin was observed, with a predominance of DAPI blocks. However, some chromosomes showed CMA blocks and other DAPI/CMA blocks. The 18S rDNA sites were distributed on the short arms of 5 pairs. In two of these pairs, such sites were in the same chromosome bearing 5S rDNA, and one of the bivalents, they were co-located. Histone H3 genes were found on one bivalent. The results added to the existing cytogenetic studies provided evidence of great karyotypic plasticity in the species. This pliancy may be the result of vicariant events related to the geographical distribution of different populations of .