Nature 193, 1210 - 1211 (24 March 1962); doi:10.1038/1931210a0

Tempero-Spatial Sequentiality of Chromosomal Polymorphism in Chilocorus stigma Say (Coleoptera : Coccinellidae)

STANLEY G. SMITH

Forest Insect Laboratory, Sault Ste. Marie, Ontario.

IT is axiomatic that the chromosome complements of the different individuals comprising a species are identical in number and morphology. The North American ladybird beetle, C. stigma Say (= bivulnerus Muls.), constitutes one of the more striking exceptions in that different males may possess any number of chromosomes from 25 down to 19 (females, 26–20): it is a chromosomally polymorphic species¹. The polymorphism here finds its basis in the centric fusion of non-homologous chromosomes, whereby an 'A' and a 'B' chromosome may be supplanted by an 'A + B' fusion chromosome. At meiosis two rod-shaped pairs may thus be replaced by one ring-shaped pair or, in the heterozygote, by a V-shaped configuration of three chromosomes.

1. Smith, S. G. , Experientia, 12, 52 (1956). | Article | ISI |
2. Smith, S. G. , Proc. Tenth Intern. Cong. Genet., Montreal, 1, 444 (1959).
3. Smith, S. G. , Ann. Rev. Entomol., 5, 69 (1960). | Article | ISI |