Which bugs are bad for the garden?

Arthropods that damage plant parts to the point of interfering with or terminating biological, botanical, and zoological life cycles and natural histories are bugs that are bad for the garden. A garden-friendly behavioral standard can be set by adult birds and lepidopterans, who rarely feed upon nectar and pollen to the point of exhausting the plant's ability to keep producing such food sources which simultaneously are respectively attractants for and participants in reproduction-oriented activities. A garden-unfriendly standard is found among such defilers as aphids, insects that deplete a plant's life-giving nutrients channeled by capillary action upward from roots and photosynthetic products transported downward from leaves.