Two cytotaxonomically interesting cases of irreversible autosome fusion in dragonflies: Argia moesta (Hagen) (Zygoptera: Ceonagrionidae) and Anaciaeschna isosceles (Müller) (Anisoptera: Aeshnidae)

A. moesta (London, Ontario, Canada; 2n d = 25, n <5 = 13, XO) is the first out of about 60 cy tologically examined coenagrionide spp. the chromosome number of which deviates from the usual family pattern (27, 14 resp.). Its karyotype agrees with those of the other 5 hitherto studied Argia spp. in lacking the m-chromosomes, and is characterized by an exceptionally large autosome pair (bivalent). — A. isosceles (Utrecht, Netherlands; 2n d = 25, n 6 = 13, m, XO) is the first out of 8 anactine spp. studied possessing this complement. Micrographs of spermatogonial and spermatocyte 1 metaphase are provided.