Four Neotropical tiger beetle species, three from the genus Megacephala and one from the genus Oxycheila, currently assigned to the tribe Megacephalini were examined cytogenetically. All three Megacephala species showed simple sex chromosome systems of the X0/XX type but different numbers of autosomal pairs (15 in M. cruciata, 14 in M. sobrina and 12 in M. rutilans), while Oxycheila tristis was inferred to have a multiple sex chromosome system with four X chromosomes (2n = 24 + X1X2X3X4Y/X1X1X2X2X3X3X4X4). Fluorescence in situ hybridization (FISH) using a PCR-amplified 18S rDNA fragment as a probe revealed the presence of rDNA clusters located exclusively on the autosomes in all the Megacephala species (five clusters in M. cruciata, eight in M. sobrina and three in M. rutilans), indicating variability in the number of clusters and the presence of structural polymorphisms. The same methodology showed that O. tristis had six rDNA clusters, apparently also located on the autosomes. Although our data also show cytogenetic variability within the genus Megacephala, our findings support the most accepted hypothesis for chromosome evolution in the family Cicindelidae. The description of multiple sex chromosomes in O. tristis along with phylogenetic analyses and larval morphological characters may be assumed as an additional evidence for the exclusion of the genus Oxycheila and related taxa from the tribe Megacephalini.

Metáfases provenientes de tecido germinal de oito machos e de sete fêmeas de Cicindelidia trifasciata provenientes de Cuba foram analisadas. O cariótipo da espécie não segue o padrão descrito para os cicindelídeos da região Neártica: possui 11 pares de autossomas e um sistema cromossómico sexual múltiplo do tipo X1X2X3Y/X1 X1X2X2X3 X3, sendo por isso o valor diplóide de 2n = 26 nos machos e 2n = 28 nas fêmeas. O tamanho dos dois primeiros pares de autossomas era quase o dobro dos restantes cromossomas e os elementos sexuais eram morfologicamente bem diferenciados. A população estudada é polimórfica no que respeita à existência de cromossomas supranumerários quer a nível intraindividual quer interindividual. Um cromossoma B extra foi observado em todas as metafáses de um macho (2n = 27) e todas as fêmeas possuíam metáfases com um a três pequenos cromossomas Bs, apresentando uma clara dominância do citotipo 2n = 29.

Metaphases from germinal tissue of eight males and seven females of Cicindelidia trifasciata from Cuba were analyzed. The species karyotype does not fit the pattern described for Nearctic cicindelids (2n = 18 + XXY): it has 11 autosome pairs and a sex chromosome system of the X1X2X3Y/ X1X1X2X2 X3X3 type, thus a diploid value of 2n = 26 in males and 2n = 28 in females. The first two autosome pairs were almost twice as large as the remaining chromosomes, and the sex elements were morphologically well differentiated. This population was found to be polymorphic for supernumerary chromosomes at both the intraindividual and interindividual levels. An extra small B chromosome was observed in all metaphases of one male (2n = 27), and every female showed metaphases with one to three small Bs, with a clearly higher frequency of cytotype 2n = 29.