Which two environmental factors are critical in silverfish or firebrat infestations?

The correct answer highlights that starch-based materials are critical in the context of silverfish or firebrat infestations. These pests are particularly drawn to environments where they can find food sources rich in starch, which is commonly found in items such as paper, books, and food products, especially those that are starchy or sugary. Their ability to thrive in areas where these materials are present makes them especially problematic in homes and buildings where such items are stored.

While humidity is also a significant factor in the survival and reproduction of silverfish and firebrats, as they prefer high humidity levels to prevent dehydration, the focus on starch-based materials directly relates to their feeding habits and survival strategies, indicating a stronger influence on the likelihood of infestation.

Environmental conditions like high humidity (75 - 95%) and high temperatures do support their growth but do not define their nutritional needs or the specific sources they seek out for sustenance. Cold temperatures, conversely, would typically hinder their activity and reproduction. Understanding these dietary preferences helps in formulating pest management strategies and determining where to focus control efforts.