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Aedes aegypti mosquito is the principle vector for dengue virus transmission. It is the day-biting mosquito which natually breeds in different water containers in and around houses. Dengue/dengue haemorrhagic fever (DF/DHF) is a re-emerging public health problem with > 2.5 billkm people at risk in th world with the greatest disease bilrden in Southeast Asia and the c. An understanding of genetic population structure and dispersal ability in vector populations is important basic Knowledge for effective vector control using both inventional methods and novel strategies such as genetic modification of the vectors.

The mosquitoes Anopheles arabiensis má An. gambiae s. s. are two sibling species that are the most efficient vectors of malaria across Africa. Although they occursympatrically over much of the continent, An. arabiensis predominates in hotter and drier conditions whilst An. gambiae s. s. is more abundant in wetter conditions. This study explored the physiological and behavioural factors responsible for the different spatial and temporal distributions of these species. In the laboratory adult An.arabiensis exhibit a three-fold longer survival than Art. gambiae s.s. at high temperatures and low humidity. Moreover An. arabiensis is tolerant of high temperatures that are actively avoided by An. gambiae S.S. This behavioural response to high temperatures was also observed in adult populations of both species in the field տ The Gambia. The interspecific difference observed in survival rates is not apparent in the 24 hour activity levels. Neither species could sustain periods of activity at temperatures above 30 c. An. arabiensis loses water at a proportionately lower rate at 40 c and 30%RH, and contained a disproportionately greater reserve of accessible water, namely haemolymph, than An. gambiae ร.ร. Although heat-shocked groups of both species expressed higher levels of heat shock proteins when compared to control groups, this did not relate to improved knock-down resistance. There were less obvious differences between the species in the larval stage. In the laboratory An. arabiensis larvae exhibited a greater survival to adulthood at 35 c than An, gambiae ร.ร., when reared separately and together. However, in the field An. arabieหsis did not dominate the hottest breeding sites in The Gambia in the dry season. Larvae of both species dived away from 40 c water surface temperatures, though for short periods only. It is argued that a better tolerance of hot and drying resting conditions in An. Arabiensis may result in longer-term improvements in survival rates compared to An. Gambiae S.S.

Mainland Southeast (SE) Asia harbours the Indo-Burmese 'biodiversity hotspot' (Myers et al, 2000). Despite this there have been very few phylogeographical studies carried out in this region. Here, Anopheles mosquitoes are used as model organisms fo look at pattems of genetic diversity and population history across the SE Asian mainland and to relate tliese patterns to Pleistocene climate change.

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Behavioural studies using a Y-tube olfactometer confirmed the differential attractiveness of human volunteers to the yellow fever mosquito, <i>Aedes aegypti.  </i>Volatile chemicals were collected from all volunteers by air entrainment.  The extracts were analysed behaviourally with <i>Ae. aegypti </i>and the Scottish biting midge, <i>Culicoides impunctatus </i>in a Y-tube olfactometer.  The behavioural responses were similar to those previously observed to the hands of the volunteers.  Electrophysiological responses of <i>Ae. aegypti </i>and <i>C.</i> <i>impunctatus, </i>to volatiles from the air entrainment extracts, were recorded using coupled gas chromatography-electroantennography (GC-EAG).  EAG-active compounds were tentatively identified using GC-mass spectrometry (GC-MS) and were confirmed by peak enhancement.  A quantitative and qualitative analysis of compounds within the extracts revealed significant differences in chemical profiles.  The mean absolute amounts of benzaldehyde, 6-methyl­-5-hepten-2-one, octanal, nonanal, naphthalene, decanal and geranylacetone were significantly greater in the unattractive group than the attractive group.  Similarly, the mean relative amounts of 6-­methyl-5-hepten-2-one, octanal and decanal in the unattractive group were significantly greater than the attractive group.  Five compounds caused significant reductions in behavioural responses of <i>Ae. aegypti </i>when presented alongside a human hand in the Y-tube olfactometer, thus accounting for the lack of attraction towards the volunteers’ hands in the unattractive group.  The identification of such behaviourally active compounds could lead to improved control technologies, whereby such compounds could potentially be incorporated into new, safe and natural repellents against biting insects.

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