Like all insects, ladybugs are cold-blooded, so their body temperature changes based on the external temperature. When the weather is warm, they become more active. The hot and dry weather causes insects to seek out moisture and cooler places to hang out -- like your home.

 

In specific, ladybugs are ectotherms, whose internal physiological sources of heat are of relatively small or of quite negligible importance in controlling body temperature. Ectotherms rely on environmental heat sources, which permit them to operate at very economical metabolic rates. When the weather turns cold, ectotherms bury into the ground and wait until winter. As for ladybugs, they look for warm, secluded places to hibernate, such as in rotting logs, under rocks, or even inside houses. These hibernating colonies can contain thousands of ladybugs, as shown in the image on the left.