The male reproductive system of adult Oryctes rhinoceros consists of a pair of testes with 6 follicles in each, connected to vasa deferentia by small vasa efferentia, a pair of accessory glands, a median ejaculatory duct and a chitinous intromittent organ. The differentiation of these structures in the successive instars is described in detail. In the first. second and early third (final) instar larvae the reproductive system is rudimentary consisting of a pair of testes (each testis is a rounded aggregate of 6 follicles held together in a connective tissue sheath), a pair of delicate ducts or the vasa deferentia connected to 'genital disc' at the mid-ventral aspect of the 9th abdominal sternite. A chitinous plate makes its appearance in the 'genital disc' of second instar and is discarded alongwith prepupal exuvium. In the pupa, each testicular follicle gets separated to independent disc shaped organ. The ejaculatory duct and accessory glands differentiate from the distal part of 'genital disc' whereas the proximal part gives rise to the intromittent organ. Definitive spermatogonia differentiate in the late third instar larval testis. Spermatocysts and meiotic figures are seen only in the pupal stage and spermiogenesis after adult emergence. Sperm bundles are noticed only in a 2-4·day old adult. Accessory glands release secretion in 10-14-day old adult. Gradual degeneration of testis and ducts is observed in the adults from the third month onwards.

The essential polyunsaturated fatty acids required by insects in their food appear to be needed for prcstaglandinogenesis. Prostaglandins themselves are likely to be widely distributed in insects playing perhaps an hitherto unsuspected important role as in reproduction.

Embryonic development of Dysdercus cingulatus is briefly described. In the embryos, neurosecretory cells become evident in the median, lateral and ventral aspects of protocerebrum 84 hr after egg laying. The corpora cardiaca, the corpora allata and the pro thoracic glands arise more or less simultaneously at 78 hr from the dorsolateral wall of the stomodaeum, from the mandibular segments and from the labial segments respectively. Secretory material appears in the brain neurosecretory cells and in the intrinsic cells of the corpus cardiacum at 84 hr and in the nervi corpori cardiaci and aorta at 90 hr. The cells of the prothoracic glands show signs of secretory activity at 90 hr, reaching maximum activity around 96 hr. The corpus allatum appears to be inactive in the embryo. Two embryonic moults appear between 96 hr and 110 hr. Consequence of events suggests that the neurosecretory material stimulates the prothoracic glands including embryonic moulting.

No abstract

The effect of topical application of juvenile hormone analogues farnesyl methyl ether and kinoprene (ZR 777) at different doses to eggs immediately after laying, germ band formation and blastokinesis, produced different types of abnormal embryos with varying degrees of derangement of development, most of them ultimately resulting in failure to hatch. Some of the embryos were almost normal but failed to hatch even though they continued to develop inside the chorion and died two days later. On the whole. there was correlation between dose of the analogue applied and mortality rate. Kinoprene was much more effective than farnesyl methyl ether. With given dose, per cent embryonic mortality was more or less the same whether the analogues were applied just after oviposition or germ band formation, but was lesser when applied immediately after blastokinesis, The period just after germ band formation appeared to be most sensitive. Treatments affected the endocrine system. The neurosecretory index was higher in the treated embryos. Prothoracic glands and their nuclei showed considerable enlargement in treated embryos continuing development inside chorion even after their controls hatched. The corpus allatum was smaller in treated embryos and corpora cardiaca were filled with neurosecretory material. Cuticle development was abnormal after treatment.