The First Bees of Spring
- Heather Holm
- 6 days ago
- 3 min read
We have been experiencing fluctuating spring temperatures this month with one day barely above freezing and the next day exceeding 70 degrees! The warmer than average lead up to spring has resulted in some of the earliest recorded emergence dates for early spring bees including Colletes inaequalis (unequal cellophane bee). Board member Zach Portman reported males emerging on March 21st in St. Paul, MN, the earliest he's seen this genus active in Minnesota. A few days later on March 25th in Minnetonka, MN, males began emerging from a south-facing slope where a large nesting aggregation occurs.
Life Cycle of a Solitary Spring Bee
Colletes inaequalis is a univoltine (one generation per year) solitary bee. In late March or early April, males begin emerging from their natal ground nests, approximately a week or so before females emerge. From their brood cell belowground, they excavate their way vertically until surfacing on the ground. Males often reuse these emergence tunnels shelter in overnight.
In the week following emergence, on warm days, males spend all their time patrolling the emergence area, flying just above the ground, searching for females. They rest temporarily on the ground, then launch again to begin another circuitous flight. When females emerge several days later, males quickly vie for an opportunity to mate with them. Males soon perish after successfully (or unsuccessfully) mating with a female. Females live for the next three weeks, dedicating their time to creating and provisioning additional brood cells in their nest.
If early spring plants such as red maple (Acer rubrum) or pussy willow (Salix discolor) are blooming, males patrol those flowers, circling around the plants as they search for females. Later, once females have established a nest and prepared a brood cell for pollen, they revisit these native woody plants to collect pollen.
Cellophane Bee: What's in a Name?
Bees in the genus Colletes are commonly known as cellophane (or plasterer) bees. When a female prepares a brood cell in her ground nest, she coats the soil walls with a secretion produced from her Dufour's gland, a gland located at the end of her abdomen. Using her short forked tongue, she spreads the fluid on the soil walls while combining it with salivary gland secretions; when this mixture dries, it forms a waterproof cellophane-like cell lining. This waterproof lining helps contain the liquid provisions (pollen combined with nectar) and limit soil bacteria and fungi from contaminating the provisions.
When the appropriate soil type and conditions are available, many Colletes inaequalis create nests in aggregations, which consist of numerous individual nests. Bees that cluster their nests in a single area are known as gregarious nesters.
After females have completely provisioned their nests, they perish. Meanwhile, their larvae continue to develop, consuming all the provisions stored in the brood cell. They then undergo metamorphosis, transitioning into pupae and eventually becoming adults. The adult cellophane bees spend the winter in their brood cells and emerge in early spring of the following year to produce another generation of Colletes inaequalis.