A report on the reproductive morphology of gynander tasar silkmoths Antheraea mylitta Drury (Lepidoptera: Saturniidae)

Gynandromorphs are abnormal individuals showing varying degrees of mixed sexual characters. They are known for several insect groups, but are most oftendromorphs may occur through the failure of genetic sex determining mechanisms or through hormonal or other influences during development. In the extreme case, one half of such an insect is female, the other half male. Some of the tissues are genetically and structurally female, others male. The genetic basis of gynandromorphism in Drosophila, Lymantria, Bombyx, etc. is well documented It has been recently established in mites that gynandromorphism is the result of unequal distribution of sex linked chromosomes rather than control at the gene or physiological level (Homsher and Yunker, 1981). The occurrence of gynandromorphs is very rare in both wild and commercial populations of the tropical tasar silkmoth, Antheraea mylitta. Gynandromor-phism in this moth was first reported by Sen and Jolly (1967) wherein they discussed the morphological characters with special reference to the genitalia. This note illustrates the previously unreported morphology of the reproductive system of gynander tasar silkmoths. Two types of gynandromorph were observed in a commercial laboratory population of the tasar silkmoth: predominately male gynandromorphs and predominately female gynandromorphs. In both cases, the left half of the body was observed to possess the male characters whereas the female characters occurred on the right. The male predominants have well developed testes with a male accessory gland on the left half and on the right half a single atrophied ovary with a mature colleterial gland and a female accessory gland (Fig. 1). In the case of female predominants, the reproductive organ situation was reversed. A single ovary containing four mature ovarioles with a single fully developed colleterial gland and female accessory gland was present. In these individuals the testes remained atrophied and non-functional. The female predominant condition is illustrated in Fig. 2. In both male and female predominant individuals, the genitalia retain important parts of both the female (bursa copulatrix) and male (aedeagus). It is noteworthy that predominant female gynandromorphs, after mating with normal males, laid very few eggs and these were infertile. By contrast, virgin normal females, when mated with predominant male gynandromorphs laid fertile eggs. A similar reproductive behavior has been reported in gynandro-morph Drosophila melanogaster by Napolitano and Tompkins (1989). Conventional morphological secondary sex characters such as wing maculation and antenna structure show the typical male features on the left and female features on the …