A chromosomal investigation of the west European species of Corixa Geoffroy (Heteroptera: Corixidae).

C-banded karyotypes are provided for the five west European species of Corixa Geoffroy. All have 2n = 22 autosomes + sex chromosomes which are XY (male symbol), XX (female symbol). Some specimens of C. punctata have a small B-chromosome, while some C. panzeri have a fairly large one. The karyotypes of C. punctata, C. dentipes, C. affinis and C. panzeri are all distinctive, but the karyotypes of C. punctata and C. iberica appear indistinguishable. The Scottish material of C. punctata and C. iberica used in this study shows morphological intergradation between the two, suggesting that they hybridise where their ranges overlap. Meiosis shows very fine even pachytene bands in C. punctata, and that the autosomes form true bivalents during diplotene in C. affinis and C. panzeri, while the sex chromosomes appear closely associated. At first metaphase the sex chromosomes may appear either closely associated or may have separated. There is no evidence of the presence of m-chromosomes.