23 October 2026
Fruit Flies Change Their Waterproof Wax Within Hours of Drying Out
A study from Ahmedabad University finds that the wax coating that protects insects from dehydration changes its chemistry within just a few hours.
Put a fruit fly in very dry air, and it loses roughly two-fifths of its body water in the first two hours. The fly is already responding, though. A new study from Ahmedabad University found that the wax on its body surface changes chemistry in those same few hours.
The study was conducted by Abhishek Nair, a doctoral student, at the Species, Climate Change, and Evolution Lab, led by Subhash Rajpurohit, an Associate Professor in the School of Arts and Sciences at Ahmedabad University. Colleagues from the University of Exeter (UK) and Western Sydney University (Australia) also took part.
Insects are tiny, so they dry out fast. More than 80 per cent of the water they lose leaves the body through the hard cuticle. To slow this down, insects carry a thin layer of wax made of molecules called cuticular hydrocarbons. How quickly that layer changes under dry conditions was poorly understood.
The team kept male fruit flies from a Himalayan population in sealed vials with silica gel, which absorbs moisture, for 2, 4, 6, 8 or 10 hours. They used males because they are smaller and lose water more quickly, making any effect easier to see. The team weighed the flies to determine how much water they lost, analysed the wax by washing it off the flies with a solvent and identifying its molecules using a gas chromatograph–mass spectrometer, and compared each group with flies that had not been dried out.
Water loss was fastest in the first two hours, then eased between 2 and 8 hours. The authors think the flies respond to prolonged dryness by activating a range of defences, and that the wax also shifts during this period. Shorter molecules stood out first, then longer, branched ones, which are thought to seal in water better.
At 10 hours, close to the limit of what the flies can survive, water loss picked up again. Why is still unclear. The authors’ best guess is that the flies’ outer layer starts to wear down, though they have no evidence for this yet.
The common fruit fly has spread to almost every part of the world. The authors suggest that a wax coat that adjusts quickly may have helped it settle in such different climates, though this study did not test that idea. As heat and dry spells become more common, researchers want to know which insects can keep up.
The authors also note that flies kept in humid air were not tested alongside the dried ones, so natural changes over the day can’t be fully ruled out. They plan to study the pathways and the genes behind the wax next.
