CHROMOSOMAL AND NOR PATTERNS IN THE POLYCLONAL STICK-INSECT BACILLUS-ATTICUS-ATTICUS (INSECTA, PHASMATODEA)

Bacillus atticus atticus is a complex of thelytokous parthenogens, rel ated to the bisexual Bacillus grandii, that ranges from Sardinia to Ne ar Eastern countries. Karyotypic and cytogenetic differentiation of th e B. atticus atticus diploid unisexual ''isolates'' is really higher t han expected. Its standard karyotype has 2n = 34 chromosomes, but seve ral instances of repatterned or even aneuploid complements have been f ound. The number and location of silver-stained NORs are particularly intriguing, since in addition to homozygous NOR patterns, simple or do uble hemizygous strains are found spread over specific and wide region s. The odd patterns are not due to Ag-NOR staining technique artifacts , since the FISH method, using rDNA probes, apparently labels the same ribosomal clusters. Transpositions and translocations have been sugge sted to account for some NOR patterns, but hybridizations between diff erent NOR-bearing races are also a possible cause. This chromosomal su rvey clearly contributes to a better understanding of B. atticus phylo geny.