Athol McLachlan: Pioneering Zoologist and His Groundbreaking Midge Research
The zoologist Athol McLachlan, who passed away at the age of 86, dedicated his entire career to the study of chironomid midges, tiny non-biting flies that spend most of their lives as aquatic larvae before emerging briefly as adults. His fascination with these unassuming insects led to elegant insights into how natural selection adapts organisms to fleeting environments, from rock pools on the Zomba plateau in Malawi to mating swarms beside British hedgerows.
Early Discoveries in Malawi's Rock Pools
Athol's interest in chironomid midges began in the 1960s during his doctoral research on the insects of Lake Kariba in Zimbabwe, then known as Rhodesia. He recognized that these tiny flies served as excellent model systems to test classic ideas in ecology and evolution. While chironomids form vast swarms over Africa's great lakes, Athol focused on the smallest and most overlooked habitats: shallow rain pools that form in depressions on exposed rock. These pools fill after rain, persist for weeks or months before drying out, and may recur in the same locations for thousands or even millions of years, offering a natural experiment in adaptation to predictable but transient environments.
Through successive seasons of fieldwork on the Zomba plateau, Athol discovered that each neighboring rain pool contained the larvae of only one of several midge species. By treating each pool as a tiny experimental arena and transplanting species between them, he demonstrated that species presence is not due to chance but to a small set of factors that allow one species to exclude all others. Some species were adapted to shallow, short-lived pools and could survive complete desiccation, while others required deeper, more stable habitats. This rare experimental evidence of competing species struggling to coexist provided clear confirmation of classic niche and competition theory.
Breakthroughs in Mating Swarm Studies
In the 1980s, based in the UK, Athol made a further breakthrough while studying chironomid species closer to his Newcastle home. Midge swarms are a familiar sight on summer evenings in Britain, appearing beside trees and hedgerows. Females visit the swarms to mate, coupling in mid-air before falling to the ground. In a series of studies, Athol demonstrated that, while in most animals sexual selection favors large males in competition for females, within these mating swarms the smallest males achieved disproportionate success.
His work showed that for animals that mate on the wing, small size can confer an aerial advantage, allowing these males to respond more rapidly to intercept incoming females. More generally, Athol's research revealed that where males compete in three-dimensional arenas such as air or water, agility can be favored over size or strength, a finding that has now become incorporated into sexual selection theory.
Balancing Selection and Lifespan Costs
This led Athol to question why males did not simply evolve to be smaller. Working with his student Rachel Neems, he showed that while small size conferred a mating advantage, it also carried costs. For most of their lives, these flies live as tiny larvae, known as bloodworms, at the bottom of ponds and lakes, where small size was a disadvantage. Smaller worms were pushed out of safe refuges by larger ones, exposing them to predation. Across the full lifespan, males of intermediate size proved most successful at passing on their genes, providing a particularly neat example of balancing selection.
Early Life and Academic Career
Born in Johannesburg to Elinor (nee Quine) and John McLachlan, a chemical engineer, Athol developed an early fascination with the plants and animals of southern Africa. During holidays from Longwood House boarding school in Meyerton, south of Johannesburg, he hunted insects, snakes, and lizards, honing the sharp observational skills that would define his scientific life. As a teenager, he and his younger brother, Ian, earned money by catching venomous snakes, extracting their venom, and selling it to a local medical school for antivenom production.
After finishing his schooling at Damelin College in Johannesburg, Athol studied zoology and botany at the University of the Witwatersrand, graduating in 1962 before beginning doctoral research at Lake Kariba. He received his PhD from the University of London in 1968. Postdoctoral research at the University of Malawi was followed by an appointment in 1970 as a lecturer in zoology at the University of Newcastle-upon-Tyne, which remained his academic home for the rest of his career.
Teaching and Later Years
In the 1980s, Athol established a formal academic link between Newcastle and Malawi, funded by the British Council. He was awarded a DSc degree from the University of London in 1992 in recognition of his achievements in insect ecology and animal behavior. At Newcastle, Athol was an admired, slightly enigmatic lecturer who emphasized curiosity-driven research and the puzzles hidden in everyday nature. He had a dry, laconic wit that sometimes took a moment to register and was most at home on field courses, where his skills as a naturalist were on full display.
For many years, he taught on Great Cumbrae in Scotland, turning over rocks in streams and fields, probing anthills, and pointing out battles between dung flies on cow pats and other small dramas of the natural world. In the later stages of his career, his early experience as a hunter in southern Africa found an unexpected outlet on the Isle of Mull, where he traveled each summer to assist the Glengorm Estate with deer management. There, he met the ceramic artist Charlotte Mellis, whom he married in 1993. After retiring from Newcastle in 2004, they moved to Mull, where they restored a former schoolhouse and where he continued to publish research and maintain a science blog.
Athol McLachlan is survived by his wife, Charlotte. His legacy as a zoologist who unraveled the complexities of evolution through the study of midges continues to inspire the scientific community.
