Twenty minutes of observing air-borne visitors to a patch of roadside Chicory revealed nine different species of pollinators, including bees, flies and beetles. Most of the insects were bees, which makes sense, as honeybees, leafcutting bees and ground-nesting bees are the primary pollinators of this flower. Without exception, all of the pollinating insects were covered from head to toe with Chicory’s white pollen grains. As they circled the flowers’ stamens collecting pollen, the insects’ bodies were inadvertently dusted with some of it. Thanks to these diligent pollen-collectors and transporters, American Goldfinches and other seed-eating birds will be feeding on Chicory seeds come winter. (Electron microscopy by Igor Siwanowic and Scienceworks.)
A commonly held belief is that in order to be cross-pollinated, flowers have evolved to attract certain pollinators, including wind, mammals, birds and insects. These traits, or “pollination syndromes,” include the flower shape, color, odor, amount of nectar and flowering time. Flowers attractive to hummingbirds tend to be large, tubular-shaped and colored red, orange (or sometimes yellow). These flowers usually have a large supply of dilute nectar, which they secrete during the day. Since birds do not have a strong response to scent, the flowers they visit tend to be odorless.
Canada Lilies, found throughout eastern North America, have a distinct tubular shape, which appeals to Ruby-throated Hummingbirds. Their long, thin beak allows these birds to reach nectar at the base of the flower that is inaccessible to many other creatures. In order to reach the nectar, the hummingbird must enter the flower far enough so that its neck and breast press up against the orange pollen-laden anthers of the Canada Lily. When the hummingbird moves on to the next Canada Lily flower, it is very likely that some of this pollen will end up on the flower’s female structure, or stigma, thereby pollinating the flower. (Note that the stigma, in the center of the flower, is taller than the anthers, thereby discouraging self-pollination.)
A weevil is a type of beetle whose mouthparts are formed into a long snout, with one antenna on either side of it. The snout is used not only for feeding but also for making cavities in buds, fruits, seeds, stems, and roots of plants, where eggs are laid. When the weevil larvae emerge, they feed within the plant. There are 60,000 species of weevils, all of which are herbivorous and most of which are less than ¼ ” long. The species of weevil in the photograph was on many of the black-eyed Susans that were blooming in an unmowed field, and all of them appeared to be feasting on pollen. Many weevils are pests of plants such as cotton, alfalfa and wheat. You may have even found them inside your house devouring your cereal or flour.
If you find a blossoming Trout Lily in the woods it is quite likely that you will also find one of its most common pollinators, the Red-necked False Blister Beetle (Asclera ruficollis), on it. Ardent pollen eaters, this group of beetles obtain their common name because many species cause blisters when pinched or squashed against skin. Adults mate on flower heads during pollen feeding. Both sexes feed on pollen, which acts as an attractant, but the female will not accept the male until her gut is packed full of pollen. She stores the pollen in a special intestinal sack in which an enzyme causes the pollen to partially germinate — this causes the indigestible covering of the pollen grain to rupture. She then digests the contents of the pollen grain, which she uses to manufacture eggs.
Spring Beauty (Claytonia virginica) is one of our earliest woodland wildflowers to blossom, and thus an important source of nectar and pollen for the earliest foraging insects. Pink lines (“bee guides”) on each of its five petals lead pollinators to the center of the flower, where the nectar is located. The pollinator in this image, Andrena erigeniae, is one of the more common species of bees that visits Spring Beauty in the early spring. Notice the slightly pink pollen she has gathered into the pollen basket on her hind leg. If you’re interested in spending time observing the series of different insect pollinators that visit Spring Beauty as the season progresses, there’s a golden opportunity for you. If you go to http://springbeauties.wordpress.com/ you can participate as a citizen scientist volunteer and participate in their survey.