SUMMARYQueens and workers of the honey bee, Apis mellifera. have been reared as larvae and pupae under defined conditions, and the developmental stages have been associated with unequivocal features. The larval instars are characterized by the head diameter and weight of the larvae. The stages of pupal development. are defined by the colours shown by the compound eyes and the thorax. The temporal duration of the successive developmental stages has also been determined. With these criteria a larva or a pupa can be assigned to a definite position on the developmental time axis.

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Using combined gas chromatography/selected-ion mass spectroscopy, the titer of juvenile hormone was determined for whole-body extracts at various morphologically defined stages of the life cycle of Drosophila melanogaster. Only juvenile hormone I11 (JH-111) was detected.JH-111 is present in early metamorphosis but by mid-metamorphosis it is below the level of detection (0.05 pmol/g). It then increases as the pharate adult matures and rises dramatically, beginning just prior to eclosion and reaching 5 -7 pmol/g shortly after eclosion. The titer then begins to fall again as the adults mature in both males and females, though the decrease is more rapid in females. Preliminary studies show that low levels of JH-111 are present during all the larval instars but are absent from eggs.Juvenile hormones and ecdysteroid hormones interact to regulate insect development. Both hormones are required during larval growth, and are needed for regulating adult reproduction. In Drosophila nielanoguster the titers of ecdysteroids have been determined during the life cycle by various techniques [l-41, yet the presence of juvenile hormone was only assumed by analogy with other insects [5], by the study of mutants [6], and by transplants with corpora allata [5], the usual source of juvenile hormone, although its presence has also been inferred from studies using juvenile hormone analogues [7, 81. The small size of D. melanogaster and the problems of detecting the hormone at physiological levels have meant that until recently it was not possible to measure directly the titer of juvenile hormone. By using chemical derivatization and coupled gas chromatography/ selected-ion mass spectrometry (GC-SIMS) to analyze juvenile hormone in whole insects, even very low titers can be reliably identified and quantified down to as little as 0.05 pmol/g fresh weight [9].If we are to understand the molecular mechanisms by which juvenile hormone and 20-hydroxyecdysone regulate tissue-specific expression of various genes during development, we must know when the hormones are present and their physiological titers. Since we are especially interested in the role of these hormones in the development of the gonads and the regulation of reproduction, we have measured the titer of juvenile hormone in carefully staged pupae and in adult males and females aged from eclosion. We have also made some preliminary studies during larval development. These measurements should be of value to geneticists, molecular biologists, biochemists and physiologists interested in many aspects of Drosophila development and reproduction.Correspondence to M. Bownes, Department of Molecular Biology, University of Edinburgh, Mayfield Road, Edinburgh, Scotland EH9 3JRAbbreviations. JH, juvenile hormone; GC-SIMS, gas chromatographyfselected-ion mass spectroscopy. MATERIALS AND METHODS Collection of materialDrosophila melanogaster of the Oregon R strain were reared in milk bottles on standard sugar, maize meal, agar and yeast media at 25°C. Adults were collected within 4 h of eclosion di...

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