Right: A gynandromorphic specimen of the dragonfly Sympetrum frequens Selys. Photo by Naoya Ishizawa. Data based on Mr. Ishizawa's paper: "A gynandromorphic specimen of Sympetrum frequens Selys", Tombo, 33(1-4):37-39, 1990. The left half of the dragonfly has male characteristics and the right half female.
From G. Gordh & D. Headrick, A dictionary of entomology, CABI Publishing, 2001:
GYNANDROMORPHISM denotes a "condition in which male and female features are displayed in one individual." The word is based on Greek roots: gyne = female, aner = male, morphe = form, ism = condition.
The dictionary lists the following genetic causes: "(1) partial fertilization in which sperm is delayed from penetrating Ooplasm until cleavage commences. Fertilized daughter nuclei become females, unfertilized daughter nuclei become male. (2) Dispermy (polyspermy) occurs when some eggs have two nuclei; male Spermatozoa unite with female nucleus to produce females. (3) Chromosomal elimination involves a normal female zygote that divides and a daughter nuclei loses the X-chromosome. Subsequent daughter nuclei of the X-less strain become male; the normal chromosomal complement strain becomes female."
In the case of the above specimen, the left-hand side is shorter than the right, giving the dragonfly's body an s-shape. The wings on the left hand side were smaller than those on the right, consistent with the smaller wings of males in this species.
For other examples of gynandromorphy in Odonata, see:
Gloyd, L.K., 1971, Gynandromorphism in the Odonata, The Michigan Entomologist, pp. 93-94.
Gloyd, L.K., 1975, Two overlooked references for gynandromorphic specimens of Odonata, The Great Lakes Entomolgist, p. 155.
May, M.L., 1988, Gynandromorphic specimens of Somatochlora (Anisoptera: Corduliidae), Odonatologica, 17(2):127-134.
Siva-Jothy, M.T., 1987, External and internal genital structures in a gynandromorph Onychogomphus uncatus (Charp.) (Anisoptera: Gomphidae), Odonatologica, 16:307-310.
Yokota, E. & S. Asahina, 1953, On a gynandromorph of Crocothemis serivlia (Drury) (Odon., Libellulidae), The Entomologist, 86:167-169.
For more detailed information on sex determination in insects and on gynandromorphy, see, for example:
Borror, D.J., C. A. Triplehorn, & N. F. Johnson, 1989, An introduction to the study of insects, 6th edition, Harcourt Brace College Publishers, Chapter 3, p. 60: Development and Metamorphosis: Sex Determination.
Romoser, W.S. & J. G. Stoffolano, Jr., 1998, The science of entomology, 4th edition, Mc-Graw Hill, Chapter 5, p. 149: Sex Determination and Parthogenesis.
Thanks again to Naoya Ishizawa for sending me a reprint of his article, the photo, and the suggestion for this page.