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The ‘modern evolutionary synthesis’ emphasised the role of genetic inheritance in driving natural selection; however, this is not the only means by which biological changes may be passed on to future generations. Information can also be transmitted non-genetically, and this could be an important agent of evolution. Non-genetic information can be acquired in two different ways: it can be inherited from parents (for example, through maternal and paternal effects) or gathered from the environment. Transmission of information in this manner can result in durable changes in behaviour, which allow for adaptation to variable conditions, and might ultimately bring about adaptive divergence. To investigate non-genetic transmission of information between parents and offspring, I studied the effects of being reared in the presence of an aversive stimulus, peppermint extract, on the fruit fly Drosophila melanogaster using a range of behavioural assays. The results demonstrate that naïve flies exposed to peppermint found it aversive, with exposure substantially reducing their survival; however, the offspring of flies reared in the presence of peppermint showed a significantly reduced aversion despite having no previous direct contact with the stimulus. This strongly suggests that a transmission of information (relating to preference for peppermint) has occurred from parents to offspring. This effect was preserved for four generations if the peppermint stimulus was removed from the food source after only one generation, but with continued exposure to peppermint the reduction in aversion was sustained, and a preference for peppermint may even have developed. Mutant flies lacking OrCo, Trp and Painless showed abnormal behavioural responses to peppermint, suggesting that these genes may be involved in detecting and/or responding to this aversive stimulus. These experiments demonstrate that environmental changes (i.e. the introduction of an aversive stimulus) can instigate biological modifications in D. melanogaster that are passed on non-genetically to future generations. This is most likely true for other insects and animals more generally, and further studies of additional model and non-model species will help to demonstrate the importance and prevalence of non-genetic transmission of information as a driver of fundamental evolutionary change.

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The taxonomy of the British Chloropidae is reviewed with special reference to the male post abdomen. A new secondary sexual character, the femoral comb, is found to occur in Oscinellinae. The male genitalia of each species are described and illustrated and the limits and division of genera into species groups are considered. Material collected during this study is considered together with existing material in museum and private collections and in order to stabilize the nomenclature available type specimens have been examined and interpreted. The known distribution and phenology of British species are recorded. The relationships of British Chloropidae are discussed at the interspecific and intergeneric level with reference to the world fauna. Several species are apparently undescribed and a number of species have not been recorded from Britain. The male genitalia are discussed in relation to existing generic concepts, and certain anomalies in the British genera are pointed out. The data in this thesis is related to the subfamily classification of Chloropidae, the systematic position of Chloropidae in the Diptera Cyclorrhapha and the theories of systematics in general.

Heme has been previously implicated in the function of the mammalian circadian clock but there has been no systematic investigation into the interplay between iron homeostasis and circadian rhythms. I have addressed this question in the model organism Drosophila melanogaster using two different approaches. First, I measured the amount and iron content of the iron storage protein ferritin, the activity of the iron sulfur cluster-containing enzyme aconitase and total heme content in whole bodies of Drosophila at different times during the 24-hour day-night cycle. I found no apparent fluctuation in these assays that would suggest circadian regulation of iron metabolism. Second, I tested whether RNA interference (RNAi) of iron homeostasis genes would alter the circadian behaviour of the flies. I selected 48 genes related to iron metabolism, silenced their expression specifically in cells expressing the circadian time-keeping transcription factor timeless and monitored the ability of these flies to sustain circadian rhythms in the absence of light cues. I found that when one of the two ferritin subunits, Ferritin 2 Light Chain Homologue (Fer2LCH) was silenced in clock cells the resulting flies displayed disrupted circadian rhythms in constant darkness. Expression of the circadian clock transcription factors timeless and period was disrupted in Fer2LCHRNAi flies. Inducing RNAi in restricted subsets of neurons I observed defects when Fer2LCH expression was reduced in the small ventral lateral neurons and in the dorsal lateral neurons that express the photoreceptor cryptochrome. An enhancer trap in Fer2LCH showed expression in a subset of these neurons. I propose a new role for Fer2LCH in the function of the biological clock in Drosophila melanogaster.