Britain's wasps have been unusually scarce this summer, puzzling scientists and entomologists. Researchers suspect that extreme heat, fluctuating temperatures, and a lack of food may be to blame. The few wasps that have been spotted are also smaller than usual, which could offer a glimpse into how rising temperatures might affect insect populations in the long term. As a wasp biologist, the absence of wasps has been particularly noticeable. Students often rely on wasps for research, but this year, they are hard to find. The lack of media stories about wasps is another sign something is amiss. Normally, wasps become more active in warm weather, and their colonies grow rapidly, often leading to news reports about swarms. Last year, which was also warm and hot, the media was full of stories about "plagues of wasps." This year, even professional pest controllers say it has been a quiet summer with few requests to remove wasp nests. The spring began well for wasps, with warm, dry weather allowing new queens to emerge from hibernation and start building their nests. However, the warm, dry conditions were followed by extreme heat, punctuated by cold, damp days and unexpectedly chilly nights. Such unpredictable weather may have caused queens to abandon or die in their nests, reducing the initial population of wasps to a much smaller number than usual. Insects, including wasps, have a critical thermal maximum (CTmax) – the highest temperature they can survive. For honeybees, this is around 49°C, and ground temperatures in the UK exceeded 50°C during this summer's heatwaves. Even without reaching this limit, extreme heat can disrupt an insect’s behavior and productivity. For example, bumblebees experience reduced foraging efficiency at temperatures as low as 32°C. While wasps are generally considered resilient to extreme weather, their ability to cope might be limited. Their thermoregulation behaviors and nest design help protect them from environmental changes. Additionally, their exoskeletons are coated with waxy molecules called cuticular hydrocarbons, which protect against drying out. These hydrocarbons change in structure under heat, offering better protection. However, wasps may have a lower CTmax than other social insects, around 45°C (113°F), making them more vulnerable to the extreme heat of the 2026 summer. The few wasps that have been seen are notably small. The size of adult insects is largely determined during their larval stage by the quality and quantity of food they receive. Wasps that emerge early in the season are usually smaller because the queen can only provide limited food for the first workers. By early August, as the colony grows and foraging improves, the workers become much larger. However, this year, the wasps observed are still "spring-sized," which could be due to limited food availability or the impact of extreme heat. Insect larvae reared in hotter conditions develop faster and reach pupation at a smaller size. This phenomenon, linked to global warming, may now be visible in real time this year. To help wasps, people are encouraged to share their outdoor meals with them. If a wasp approaches, it's advised not to shoo it away but to observe its behavior. If it's looking for protein, like picnic ham, it might be trying to feed its young. If it's searching for sugar, like jam, it might be seeking its own nutrition. Researchers also invite people to share their observations of wasps, including photos of them eating, to contribute to the Wasp Picnic Survey 2026: Ham or Jam?