An artificial diet containing 2% L-ascorbic acid was given to silkworm (Bombyx mori) larvae throughout larval life, or only in some larval instars in order to make a comparison of larvae fed on a diet without L-ascorbic acid throughout larval life. Obtained results show that, when complete L-ascorbic acid deprivation is done during the larval cycle, it affects larval growth and cocoon production. Furthermore, L-ascorbic acid absence from larval food, particularly during the first and last instars, generates beneficial effects to cocoon production without affecting the survival rate or delaying the larval cycle.

To investigate the role of juvenile hormone (JH) in caste determination, first and second instar larvae of Bombus terrestris were topically treated with one of three doses (2, 10, or 20 μg/larva) of JH dissolved in acetone. Treated larvae belonged to very young colonies that had just been started by their queen. Therefore, all larvae were supposedly destined to develop into workers. Our study demonstrates that a single application of JH in the first or second instar can lead to the development of queens and that this effect is dose‐ and instar‐dependent. The brood (second, or third brood of the colony) to which the larvae belonged also had an effect. A clear size dimorphism of the female castes exists in B. terrestris. In this study, however, intermediates also developed from treated larvae. In fact, even untreated larvae in a treated colony developed into queens and intermediates, depending on the total dose of JH applied to the colony. There are no indications that a larva, once determined to become a queen, can be forced to become a worker by means of malnutrition. Treatment with JH also had an influence on colony processes. For instance, the appearance of queen larvae resulted in the advanced start of reproduction by workers and egg robbery, the so called competition point. This indicates again the close relationship between queen rearing and the queen‐worker conflict. However, the ultimate function of this casual connection is still unclear. Further, the queen reacted to the treatment by switching to the laying of haploid eggs at an earlier date in the colony development compared to untreated colonies.

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Serotonin (5-hydroxytryptamine, 5-HT) is well known to be involved in many aspects of bivalve biology, especially in the control of reproductive function. In this work, a neurochemical and immunohistochemical study was carried out in the visceral ganglion of Venus verrucosa (Bivalvia: Veneridae), with the aim of elucidating the features of 5-HT neurotransmission and its influence on gamete emission in this poorly investigated bivalve species. 5-HT release was characterized: tritium efflux, evoked from the isolated [3H]5-HT preincubated visceral ganglion by high potassium concentrations, was shown to possess the characteristics of neurotransmitter release (sodium and calcium dependence, auto-feedback regulation). Serotonergic cell bodies and axonal tracts were labelled by immunohistochemistry, confirming that the released 5-HT originates in a pool of neurons in the visceral ganglion. \ud The presence and distribution of serotonin was immunohistochemically checked in the gonads as well. A plexus of immunopositive fibres was observed in the gonadic tissue of both sexes, specifically located in the follicle walls, and this innervation appeared to come from branching of the cerebro-visceral connectives, whereas no peripheral serotonergic neurons were identified. The immunohistochemical data were supported by light and electron microscope observations.\ud Exogenous 5-HT was applied to Venus verrucosa specimens by intramuscular injection; it induced spawning in both sexes; the response rate was significantly higher in males than in females, as previously observed in some other species of gonochoric bivalves. These findings suggest the existence of a serotonergic neurotransmission in Venus verrucosa, possibly regulating the reproductive process

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