Chromosomal analysis of Neohydrocoptus jaechi (Wewalka) and Canthydrus diophthalmus (Reiche & Saulcy) (Coleoptera : Noteridae)

Neohydrocoptus jaechi (Wewalka) is recorded for the first time in Egypt. It is very similar to N. angolensis (Peschet), but there are aedeagal differe nces. The karyotype consists of 6 pairs of autosomes and sex chromosomes wh ich are neo-XY (male) and neo-XX (female). C-banding shows that the sex chr omosomes of Canthydrus diophthalmus (Reiche & Saulcy) are not the small pai r suggested by Bilton (1992), but are one of the largest pairs, with the Y- chromosome totally heterochromatic. The implications of these findings are considered in the light of Belkaceme's (1991) work on the phylogeny of Note ridae. Neohydrocoptus is placed among the group of more primitive genera, o utside the closely-knit group of higher Noteridae, while Canthydrus is plac ed right at the top of the higher Noteridae. The neo-XY sex chromosomes of Neohydrocoptus could be a primitive condition for the family, while the sys tem found in Canthydrus is derivable from that of Synchortus Sharp (Saleh A hmed et al., 1997) (one of Belkaceme's basal genera of the higher Noteridae ) by loss of the mainly heterochromatic X-2-chromosome, leaving the more no rmal X-1-chromosome and the Y, which is almost entirely heterochromatic in Synchortus and completely so in Canthydrus.