Native Bees

Did you know that native bees pollinate approximately 80% of flowering plants around the world? There are roughly 4,000 species of native bees in the United States. In Pennsylvania alone there are over 300 different species of native bees. Perhaps surprisingly, the honeybee is not one of them. Honeybees were originally imported from Europe in the 17th century.

Nesting and life cycle:

Considered to be gentle as they rarely sting, the majority of native bees are solitary species; the others are social species. Solitary bees are those for which a single female bee creates and provisions a nest for her offspring. For nesting locations, about 30% of solitary bee species use existing cavities such as abandoned beetle burrows or other tunnels in snags (dead or dying standing trees) or within pithy, spongy stems of plants such as Joe Pye weed and Elderberry. The other 70% create nests in the ground, digging tunnels in bare or sparsely vegetated, well-drained soil. Mason, Leafcutter, and Miner bees are some of the most common examples of native solitary bees.

Solitary bees live a one-year life cycle. During the spring, adult bees procreate and the female bees prepare and provision nests for the next generation. As mentioned above, the female bee builds a nest underground or in a cavity. Within each cavity are cells where the female collects pollen and lays an egg. As she forages for nectar to feed herself, she collects pollen, brings it back to the nest, and makes it into a ball called "bee bread". This will be the food needed for one growing bee. The female lays an egg on the bee bread and seals up the nest. Soon after, the parent female and her generation of male bees die. During the summer, the eggs hatch, and the larvae begin feeding on the bee bread. After feeding, the larvae pupate over the winter within the nest. In spring, they emerge as adults from the nest and begin the cycle again.

Social bees live together and share the chores among queen bees and workers. Chores include laying eggs, searching for nectar and pollen, defending the colony, and caring for the young. Bumblebees are the only bees native to North America that are truly social.

Like solitary bees, social bees live a one year life cycle. They build colonies in abandoned rodent holes and other preexisting burrows to nest. During summer, new queens and male bees hatch and then leave the colony to mate. The rest of the bees in the colony work together to provision the nest to feed the young when the eggs hatch and to guard the nest as the young develop into adult bees. When the temperature drops, the male bees and the worker bees die. The mated queen finds a place to hibernate for the winter, usually underground. She emerges in spring, begins to forage, builds a new nest, and begins to lays eggs. By late summer, the new queen and male bees will hatch, leave the colony and the cycle will repeat.

Foraging:

About 20-45% of native bees are pollen specialists meaning that they use only pollen from one species (or genus) of plants. An example of an extremely selective (oligolectic) solitary bee species is the squash bee; who seeks out squash and pumpkins. There are also bees that gather pollen from just one species of flower (monolectic). Because of such a restrictive diet, these bees are particularly vulnerable to changes in their habitat. If that plant is removed, the bee goes away. If bees are removed, the plant doesn't reproduce. Some of the native bees are specialists on the very plants that we use for food, including squashes, pumpkins, gourds, and the annual sunflower. Social bees and the majority of solitary bee species are polylectic, meaning they gather nectar and pollen from a wide range of flower types and species. The length of their tongue determines which flowers they select. Short-tongued bees can reach nectar from open flowers like daisies while long-tongued bees can drink from more complex flowers such as lupines and lobelia. While foraging, pollen grains attach to the hairs on a bee's body and get transferred from the flower's male structure (anther) to the female structure (pistil) which is how the plant reproduces. More pollen is transferred this way by bees than any other pollinator insect which is why bees are considered to be the most important pollinator. Bees mainly forage for two things: nectar for energy and pollen to feed their offspring. They may fly up to a mile from their nest in search for food. However, the shorter the distance bees have to fly to find food sources, the more efficiently they can forage and provide for their offspring. Besides nectar and pollen, some bee species also forage for nest-building materials. They gather and carry plant resins or tissues or mud and pebbles to use in the construction of their nests. For example, Mason bees use clayey mud to build walls to protect each egg within the nest. Female Leafcutter bees use tiny pieces of leaves or flower petals to construct their nests. They chew the plant pieces until they are pliable and push it up along the walls of the cavity of the nesting chamber.

How to attract bees:

Almost 75% of flowering plants rely on pollinators for reproduction. So, to entice them, plants use pollination syndromes - the flower shape, size, color, odor and bloom time that help bees find the nectar and pollen they seek. Pollination syndromes help the plant reproduce by ensuring its pollen will be carried to another flower of the same species.

How bees carry pollen:

Most bees carry pollen on their hind legs within specialized branched hairs. However, the Leafcutter and Mason bees carry pollen on the hairs underneath their abdomen.

Threats to bee species population:

Development and agriculture are the main causes for the loss of critical habitat. It degrades and fragments habitat by removing the plants and resources bees rely upon for food, shelter, nesting, and overwintering sites. Pesticides, that are meant to control harmful insects, extend to beneficial pollinator insects and are a contributing factor in their declining populations. Additionally, climate change, specifically the warming of the planet and changes in weather patterns contributes to bee species decline. It is altering the synchrony between flowering plants and their pollinators, causing nutritional stress. And, with the introduction of commercial bees used for pollination, an increase of parasites and diseases attack and decrease native bee populations.

Ecological and economic consequences of bee population decline:

According to the USDA, bees pollinate about 75% of all the fruits, vegetables, and nuts in the United States. Every fourth bite of food people take is courtesy of bee pollination which adds to the $15 billion in increased crop value every year. Bees are essential to the reproductive cycle of most flowering plants that animals rely on for food and shelter. With fewer bees come less pollinated plants which would result in a decline in availability and variety of fresh produce and thus cascading down to a decline in human nutrition.

How Project NatureScape promotes native bee population:

The Penn State Master Gardeners of Monroe County have created a habitat restoration demonstration garden called Project NatureScape (PNS) located at the Western Pocono Community Library in Brodheadsville, PA. The garden features native plants the average homeowner can incorporate into their backyard which attracts pollinators like bees, butterflies, and wasps. The PNS garden aims to teach the public the importance of providing all our pollinators with a safe habitat so that they can continue to pollinate the plants that both humans and animals depend on.

Ways people can use their garden and landscapes to help native bees:

1) Mowing: reduce the frequency of mowing to allow dandelions and clover to bloom.

2) Create a pollinator-friendly landscape by maintaining sunny, open conditions. The sun's warmth enables the pollinators to be active, and seeing the sky allows them to navigate.

3) When possible, leave tree stumps, snags, and downed logs to promote bee nesting habitat.

4) Plant native plants with diverse bloom times throughout the growing season. Start off with some early blooming woodland phlox (Phlox divaricata), foamflower (Tiarella cordifolia), and golden alexander (Zizia aurea). For mid-spring: wild indigo (Baptisia australis) and spiderwort (Tradescantia viginiana). During the hot summer months: bee balm (Monarda fistulosa), black-eyed Susan (Rudbeckia hirta), and coneflowers (Echinacea purpurea). And don't forget fall blooms: New England asters (Symphiotrichum novae-angliae) and common sneezeweed (Helenium autumnale).

5) Color-block your garden. Pollinators are most attracted to large blocks of color and forage most efficiently where the same flower species are clustered together.

6) Maintain patches of uncovered ground in well-drained areas to promote ground-nesting bee habitat.

7) Minimize or eliminate the use of insecticides and herbicides.

8) Grow native plants!

Article written by Catherine Emgushov, Penn State Master Gardener, Monroe County

Resources

Xerces Society. Attracting Native Pollinators: Protecting North America's Bees and Butterflies. North Adams, MA: Storey Publishing, 2011

Xereces Society: Wild Bee Conservation

USGS: What is the Role of Native Bees in the United States

Cathance Educational Alliance: Discover Native Bees as Pollinators

USDA: Bolstering Bees in a Changing Climate

Colorado State University Extension: Where Do Bees Go in Winter?

Photo credits: pixabay.com