Mick Gillies

Mick Gillies, who has died aged 79, devoted most of his life to research on African malaria mosquitoes, among them one described as "the most dangerous animal in the world". By transmitting the causative agent of malignant malaria, Anopheles gambiae is responsible for more than 1m deaths in Africa each year.

At Winchester College, Gillies already had a fondness for natural history. He was taught fly fishing by his father, and at 15 took up his father's suggestion that he study mayflies, a part of the diet of fish. He retained a lifelong fascination with these aquatic insects. Gillies followed his father into medicine, and in 1945-47 served as an army medical officer in India, Malaya and Hong Kong (also indulging his passion for natural history).

He completed his medical training in England in 1948, and then spent a year as the medical officer of the British embassy in Moscow. This was a critical time for Gillies; his love of natural history and fascination with the tropics led him to forsake medicine.

In 1950, after training, he joined the East African Institute of Malaria as an entomologist, and for 12 years worked in Tanganyika's coastal foothills, where malaria was rife. Following the birth of independent Tanzania, Gillies spent two years working on mosquito taxonomy at the British Museum (natural history). In 1966, supported by the Medical Research Council, he set up a mosquito behaviour unit, with laboratories at Sussex university and a field station in the Gambia. His research projects involved months or years of work, always preceded by careful planning.

When it was important to know how far Anopheles mosquitoes could fly, Gillies reared 132,000 mosquitoes in the laboratory and marked them, either individually with a paint spot or in batches with radioactivity. They were released in the field and as many as possible recaptured in 110 trapping stations. He found that the average distance flown before capture was just under a mile, while some flew over two miles; the direction of movement was governed by the distribution of human settlements.

Mathematical modelling had shown that for mosquitoes to transmit malaria, they must live for a number of weeks, first feeding on an infected person to acquire the parasite, then surviving for 10-14 days while the parasite develops, and finally feeding again on an uninfected person to transmit the parasite.

It was not known how long mosquitoes lived in nature. Hearing of a Russian technique to establish the age of wild mosquitoes, Gillies traced the source to a Moscow library and translated it into English (he had learned Russian in his embassy years). The formidably difficult technique involved examining a female mosquito's ovaries for minute dilations that accumulated each time she had fed and produced eggs. Fortunately, in 1958 Gillies was joined by TJ "Tony" Wilkes, one of three or four people in the world with the skill to apply this technique consistently.

His analyses of more than 10,000 females, of three mosquito species, showed that approximately 80% of infections were transmitted by a small percentage of long-lived mosquitoes. This indicated that if mosquito life spans could be shortened by insecticide application malaria could be controlled. Control has been achieved in some parts of the world, but not in tropical Africa, where the numbers of mosquitoes are overwhelming.

In West Africa, Gillies and Wilkes undertook field experiments on practical problems. At what speed do mosquitoes fly, and how is their flight affected by wind? At what height above ground do they fly, and can their approach be blocked by high fences? Over what distance can they detect and fly to their human or animal hosts? That these studies produced much useful information was due as much to Gillies's exceptional experimental skills as to his patience and willingness to persist until success was achieved.

On first acquaintance, Gillies might have appeared shy or reserved, because he always thought carefully before speaking. To those who knew him better, he was a very warm person, wise with a fine sense of humour. He is survived by his wife, Eva, and two daughters.

Michael Thomas Gillies, medical entomologist; born September 15 1920; died December 10 1999

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