If you look closely at the ground directly in front of this female Black and Yellow Mud Dauber wasp you will see the clump of mud that she has collected and rolled into a ball with her mandibles. This lump of mud will be carried back to the nest site in the wasp’s mandibles, and then used as building material to mold a cell. After making the mud cell, the wasp then goes and locates spiders, stings them (paralyzing but not killing them) and brings them back to the cell, into which she packs them. When the cell is sufficiently stuffed with spiders, she lays an egg and seals the cell with more mud. She makes and fills several of these cells and typically covers all of them together with a final layer of mud. When the wasp egg in each cell hatches, the larva has living spiders to eat that haven’t decomposed, due to the fact that they are not dead. Eventually the larval wasp pupates and the adult wasp chews its way out of the cell.
Having known since childhood that most insects have only one pair of antennae, imagine my surprise when I came upon a hornet on Queen Anne’s Lace that appeared to have two: a pair of slender, black antennae, and between them, a shorter pair of white ones. A bit of research revealed to me that in fact, these white “antennae” were actually the pollen sacs (pollinia) of an introduced and somewhat invasive orchid, Broad-leaved Helleborine (Epipactis helleborine).
Broad-leaved Helleborine is entirely dependent on insects to spread its pollen, especially wasps. It attracts them with nectar, which is said to have an alcoholic and narcotic effect which may help with the spreading of pollen, as an inebriated wasp is less likely to clean pollen off its body before leaving. Helleborine also produces a chemical which other plants produce and use to signal that they are being attacked by insects. It is used purely as a ruse by Helleborine, in order to attract wasps, Helleborine’s primary pollinators, who arrive to fend off other insects, and end up inadvertently collecting Helleborine’s pollinia.
Unlike the pollen of most plants, Helleborine’s pollen grains are so sticky that they cannot separate – thus, the entire package of pollen remains intact and is removed at one time. Wasps are capable of reaching the plant’s nectar without disturbing the pollinia, but cannot crawl out of the flower without striking against and detaching them and in so doing, getting them stuck to their heads. Can you find the pollinia in the insert photograph of a Broad-leaved Helleborine flower (which has not been visited by a wasp yet)?
Due to computer issues, Naturally Curious will resume posts next Tuesday, August 16.
Cellophane bees are one of the first bees to emerge in the spring, sometime between March and May. These solitary bees nest underground, often in close proximity to one another, with each female digging her own burrow off of which she creates several individual brood cells. Each cell is lined with a cellophane-like secretion which is applied with her short brush-like tongue to the walls of the cell. She then fills the lower portion of the cellophane sac with pollen, nectar and some glandular material, lays an egg and seals the cell with more cellophane-like substance and a bit of sand for a cap. The female then goes on to repeat the process and digs another cell.
The egg hatches and the larva grows throughout the summer, feeding on the supply of nectar and pollen contained within the cell. The larva metamorphoses in the fall and overwinters as a pupa inside the natal cell, emerging as an adult on a warm, sunny spring day.
Males, which emerge before the females, can currently be seen patrolling the area where last year’s burrows were constructed, flying just an inch or two above the ground, searching for emerging females digging themselves out of the ground. When a female is spotted, she is often bombarded by one or more males, creating quite the cluster of bees. One male prevails, mating takes place, and the cycle continues.
If you research bald-faced hornet nests you will find that their average size is often compared to that of a football or basketball. The maximum size is said to be between 14 and 18 inches in diameter, and up to 23 or 24 inches in length. The pictured nest (which hung 20 feet above the roof of my house) measures 14 inches wide and 29 inches long – far larger than the average hornet nest!
This entire nest was built in roughly four months. It was started by a queen bald-faced hornet that, after emerging from hibernation this past spring, chewed some wood fiber, mixed it with her saliva and created a few brood cells surrounded by one or more paper “envelopes.” She laid an egg in each cell, and fed the hornet larvae insects which she first masticated into tiny bits. When the larvae pupated and emerged as adult workers, they assumed the duties of nest building, food collection, feeding the larvae and protecting the nest, while the queen continued laying eggs in horizontal tiers of cells. This ongoing activity produced a colony of anywhere from 100 to 400 workers by the end of the summer. Shortly before the first hard frost this fall, the queen left the colony and found a protected spot in which to spend the winter. When freezing temperatures arrived, the workers all died, leaving a nest that will never again be inhabited by bald-faced hornets. (Thanks to Nick Burnham, who ingeniously managed to collect the nest for me, and Gary Trachier for the photo.)
With frost just a whisper away, and in some areas not even that, there are still hardy plants, many in the Composite family (goldenrods, asters, thistles, Queen Anne’s Lace, Yarrow), which defy the odds and optimistically send forth blossoms on the off chance that there are still pollinators on the wing. Fortunately for them, bumblebees can and do fly at much cooler temperatures than honeybees and other pollinators. When food is plentiful and outside temperatures fall below 50°F., bumblebees generally stay inside their nest and live off their stores. At times when food is scarce or stores are low, they will forage when the outside temperature is as low as 43°F. (In severe conditions they have even been known to vary their flying height to and from the nest to take advantage of any temperature differences.) Locally, Tri-colored Bumblebees (Bombus ternarius) have a near monopoly on the last vestiges of nectar and pollen (see photo).
From the size of the chunks of sod that were ripped out of the ground in order to access this subterranean yellow jacket (Vespula sp.) nest, one can deduce that a black bear, not a striped skunk or raccoon, was the nocturnal visitor. Usually there is little intact nest left after a bear tears it apart in an effort to find yellow jacket larvae, but in this case, a portion of the paper nest remained. Apparently undaunted, even with frost in the air (signaling the demise of all the yellow jackets except young, fertilized overwintering queens), the workers lost no time in rebuilding their nest. Twenty-four hours after their nest was torn apart, the colony of yellow jackets had diligently chewed enough wood fiber to have replaced much of it.
Unlike a hive of honeybees, where the queen and workers overwinter, the only bees in a bumblebee colony that live through the winter are young, fertilized queens. In early fall, bumblebees begin producing new queens as well as males in order to allow the colony to reproduce. Once the adult virgin queens and males have emerged from the silk cocoons within their pupal cells, they leave the hive. The male bees spend their time feeding on nectar and trying to mate with the new queens and the young queens mate with several males. Once fertilized, the queens continue to feed, building up fat bodies for the approaching winter. Once enough fat bodies are stored, queens begin searching for suitable overwintering locations. Overwintering sites are often in an abandoned chipmunk or mouse burrow, or in soft soil or compost, where they can survive temperatures down to – 5° F. due to a kind of “antifreeze” they produce. The rest of the hive (old queen, workers and any remaining males) dies once cold weather arrives. In the spring the queens emerge and start new colonies. (Thanks to Natalie Kerr & Sadie Brown for making this post possible and accurate.)
Photo by Sadie Brown: A recently-excavated underground colony of bumblebees (by a chemical-free “pest” controller) contained several wax pupal cells, as well as wet, silver-haired bumblebees (their color appears as they age) emerging from some of the cells. At this time of year, they are most likely to be queens or drones.