Spring's Cool Weather Delays Insect Activity, But Scientists Predict Rapid Surge as Temperatures Rise

The unseasonably chilly and wet spring weather across North America has significantly impacted insect populations, keeping many species dormant longer than usual, but entomologists warn that warming temperatures will trigger a rapid surge in bug activity in the coming weeks.

Christine Noronha, a research scientist with Agriculture and AgriFood Canada based in Charlottetown, Prince Edward Island, explains that insects have remained relatively inactive during this spring's cooler-than-normal conditions. "They tend to stay quiet when it's cold," Noronha told CBC's Island Morning. "If this continues for very long, then it starts to have an impact on their survival and their movement."

The delayed emergence reflects insects' dependence on external heat sources for survival and activity. Unlike mammals that generate their own body heat, insects are cold-blooded creatures whose metabolism and movement patterns are directly influenced by ambient temperatures. Insects are cold blooded, and their metabolism and activity is very greatly influenced by the temperature of their bodies, which temperature is almost entirely dependent on that of the surrounding environment, according to scientific research.

The temperature threshold for most insect activity begins around 15 to 20 degrees Celsius (59 to 68 degrees Fahrenheit). The minimum temperature for flight is no lower than 12.2º C (54º F) once light level exceeds that which occurs after 8:00 a.m. in May – July except on very overcast days, research from the University of Maine indicates. Below these temperatures, many species enter what scientists call a "chill coma," where development and movement cease until favorable conditions return.

However, there's a silver lining to this spring's cooler weather. Noronha notes that bug survival rates have actually improved in recent years due to milder winters across the region. "With the spring being so cool, the insects are a little bit slower coming out," she said. "They wouldn't be feeding as much as well, [or] just moving around too from plant to plant or from one area to the next. But [when] it does warm up, then you'll start to see them feeding a lot more, moving, flying around, moving from plant to plant… and also laying their eggs."

This delayed activity pattern is particularly noticeable in bumblebees, which demonstrate clear behavioral changes throughout the day based on temperature fluctuations. "Bumblebees, for example, are kind of slow in the early morning when you see them, but then later on in the day, if it's sunny, they'll start moving around a lot more," Noronha explained. When the sun is shining, insects can be observed basking in sunlight to heat their wing muscles sufficiently for flight.

Research indicates that increased winter survival and warmer temperatures allow insect populations to build up much more rapidly in spring, leading to an increased number of generations per year and summer outbreaks. This phenomenon suggests that once temperatures stabilize, the delayed spring activity could result in more concentrated periods of insect emergence and reproduction.

Large female bees, which have been emerging from their winter locations throughout the spring, are currently searching for suitable nesting sites. These queens, often spotted around windows and heated buildings, are preparing to establish new colonies. Noronha explains that insects in fall seek out buildings because of radiated heat, and now they're transitioning to nest-building behavior that will define the summer season's ecosystem dynamics.

Unfortunately for humans seeking relief from biting insects, mosquitoes and black flies remain largely unaffected by the cooler temperatures. "Mosquitoes and black flies and all that are doing fine," Noronha said. "They have a lower temperature range, so they are fine. They are out there." These species operate effectively at lower temperature thresholds, making them among the first to become active as spring progresses.

The ecological balance remains intact despite the delayed insect activity. Tree swallows and other insectivorous birds, along with frogs and minnows that feed on mosquito and black fly larvae, continue to find adequate food sources. "All those animals are doing fine, so it's just a slower process," Noronha noted. "They're not getting as much to eat. But things haven't really come to that point where other animals are more active and insects are not."

Public health considerations remain important as insect activity increases. Noronha emphasizes the continued risk of tick-borne diseases, particularly Lyme disease, as people spend more time outdoors. She recommends wearing long pants with long socks when walking through tall grass or wooded areas, and conducting thorough tick checks upon returning home. If a tick is found attached to skin, it should be removed carefully, preserved in a container, and identified by health professionals.

For those encountering unfamiliar insects around their properties, Noronha advocates for identification before taking any control measures. Using resources like iNaturalist and other online platforms can help distinguish between beneficial predatory insects and potential pests. "It's only when you know what something is that you can actually control it – or know if you need to control it or not," she explained. "The good bugs that are predators, you don't want to kill them, right? You want to keep them in the area."

Climate research suggests that changing weather patterns will continue to influence insect populations and behaviors. Once development resumes in the spring, exposure to temperatures below 50°F can cause insects to enter a chill coma, where development and movement cease until favorable conditions resume, according to Iowa State University's Integrated Crop Management program. Recent studies indicate that years with moderate mortality like this though can be one way to have slight reductions in populations that can mean the difference between a manageable season and potential outbreaks.

The current spring's weather patterns align with broader climate trends affecting insect populations worldwide. While this year's cooler temperatures may provide temporary relief from some pest species, the underlying trend toward warmer conditions suggests that future springs may see earlier and more intense insect activity. Understanding these patterns helps both scientists and the public prepare for the ecological changes ahead.

As temperatures continue to rise through late spring and early summer, residents can expect to see a marked increase in insect activity across all species. The delayed start may actually concentrate the peak activity period, making effective preparation and awareness even more crucial for anyone spending time outdoors during the coming months.