Changes in the weather can make it difficult to control insect infestations, especially warm weather. Increased temperatures, warmer winters, increased precipitation and droughts cause the development of new insect species and invasions. On the other hand, fewer insects survive the cold weather, which decreases spring infestations. How Does Cold Weather Affect Insects? According to the University of Illinois, insects are cold-blooded which means their body temperature adapts to their environment. Most summertime insects can't develop if the temperature goes below 50 degrees Fahrenheit. If the temperature goes below freezing, insects become dormant. Depending on the species, many insects die in freezing weather. Insects that hatch in the spring can survive 20-degree temperatures and become active at 50 degrees Fahrenheit. For example, Japanese beetle grubs and dung beetles bore into the ground 10-inches deep. The freezing temperatures won't affect them at all. Most insects won't survive if the temperature hits the teens. This results in less plant and tree damage in the spring. Cold weather keeps insect reproduction and growth to a minimum, helping to control the spread of pests. Some insects, like the Monarch butterfly, avoid the cold weather altogether, migrating to Mexico in the fall. They reproduce in the warmer climate and then migrate north in the spring. How Do Mild Temperatures Affect Insects? Mild winters result in increased populations of insects that would normally die in the cold weather. Warmer weather also causes more insect reproduction and maturation. Since the insects mature quicker in warm weather, they can travel further. Many insects unknown in certain areas will travel further distances causing invasive infestations and damage. Of course, other factors other than weather also contribute to insect infestations. Mild or cold weather also increases or decreases the natural enemies of insects. So, if the mild weather helps insects reproduce, it also increases reproduction of insect-eating birds, rodents and reptiles that keep insect populations down. When considering all the ecosystem factors, from deep freezes, mild winters, natural predators and adaptive abilities, it's difficult to determine the climate effect to insect populations.