What bugs materialize out of nothing?

Bugs that seem to materialize out of nothing are often the result of a process called "spontaneous generation," which is a historical belief that life can arise from non-living matter. In reality, many insects, like flies or gnats, can appear suddenly due to their rapid reproduction cycles and the presence of organic matter for breeding. When conditions are right, such as warmth and moisture, dormant eggs or larvae can hatch, creating the illusion that they came from nowhere. However, they actually stem from previously existing life forms.