Cytology of the Grasshopper Genus Circotettix

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Abstract
Four spp. of Circotettix are examined with particular reference to cytological variation. The number of chromosomes found most often in this genus is 21. C. rabula and C. undulatus have up to 3 asymmetrical bivalents; C coconino and C. crotalum have one. Supernumerary chromosomes are present in some samples of C. rabula and C. undulatus. A California-Nevada border sample of C. undulatus has males with 21 and 23 chromosomes and natural hybrids with 22 chromosomes. In these hybrids, 3 autosomes form a trivalent in some cells or a bivalent and univalent in others. Non-disjunction is calculated at 28.8% as a result of orientation of these three chromosomes. Polyploid cells occur in several individuals of 2 spp., but excess hetero-pycnosis indicates that these degenerate.