Plants need insects to spread pollen from the male part of one flower to the female part of another flower. This fertilizes the plant so it can produce fertilized seed and reproduce. Plants that depend on insects compete for the insects' attention by producing colorful flowers or strong scents. When pollen is transferred from one flower to another with the help of animals it is called Biotic Pollination.
Bees are the most noticeable visitor to large brightly colored flowers. Although flowers compete for the attention of bees so they can be pollinated, bees cannot see the color red very well so red flowers are often passed over in favor of yellow, blue or purple flowers. Female bees eat some of the pollen for fuel and in the process collect it on the tiny hairs on their back legs called scopae. When mixed with nectar, the pollen stays on their legs, and they carry the pollen back to the hive to feed to the larvae.
Butterflies are not as efficient as bees when it comes to spreading pollen. However, the quantity of flowers they visit makes up for their inefficiency. Pollinating the flowers is a by-product of their insatiable need to consume nectar. The pollen sticks to the tiny hairs on their legs during the nectar drinking process and is transferred from flower to flower fertilizing the flowers. Some varieties of butterflies that pollinate flowers include giant swallowtails, monarchs, viceroy swallowtails and black swallowtails.
Beetles spread pollen by crawling over the pollen producing parts of the flower and eating the pollen. Beetles were the first insects to begin pollinating flowers in prehistoric times. Many times they eat the petals of the flowers that they pollinate, leaving the center of the flower to produce the fertilized seed. Some species of beetle that pollinate flowers include Nitidulid beetles, the Red-Blue Checkered Beetle, the Hoplia Beetle and the rose chafer.
Not all flies, such as the common housefly, spread disease. Many flies are beneficial. For example, the hover fly that hovers over brightly colored flowers and looks like a tiny bee or wasp, consumes the nectar and helps pollinate flowers as the pollen becomes attached to their legs while they work. The larvae, or baby hoverflies, eat aphids, a major garden pest.