An online resource based on the award-winning nature guide

Hymenoptera

Pruinose Squash Bees

8-17-17 pruinose squash bees2 049A2916The Pruinose Squash Bee (Peponapis pruinosa) is most often noticed when it’s gathering nectar or pollen from squash, pumpkin, watermelon or gourd blossoms.  (Squash bees have been shown to be excellent pollinators of zucchini and butternut squashes, among others. If numerous, they thoroughly pollinate all available flowers, rendering later visits of honeybees superfluous. Before Europeans brought honeybees to the New World, squash bees were busy aiding the adoption, domestication, spread, and production of squashes and gourds by indigenous peoples throughout the Americas.) The bee’s black and white striped abdomen is easy to recognize.

While female squash bees are busy foraging for pollen in the flowers of plants in the Cucurbitae family, male squash bees can be seen darting between flowers, searching for mates. By noon, they are fast asleep in the withered flowers.

Pruinose Squash Bees are solitary bees, with every female digging her own nest in the ground. These consist of vertical tunnels that end with a number of individual chambers that are a foot or two deep in the soil. Each chamber is provided with an egg and a lump of pollen so that when the egg hatches, food is readily available. (Photo: five Pruinose Squash Bees packed into a single Bindweed flower)

 


Bumble Bee Queens Searching For Nest Sites

5-1-17 bumblebee 008This is the time of year when queen bumble bees have emerged from hibernation and are exploring for good nest sites, using both sight and smell. When searching for a suitable place in which to build a nest, a queen bumble bee flies in a distinctive zig-zag pattern low over the ground. If a certain cavity or hole interests her she will land on the ground and investigate by going into the crevice or hole.

Nest sites vary between bumble bee species. Most of the more common species prefer dry, dark cavities. Some nest underground, in places such as abandoned rodent holes, under sheds and in compost heaps. Of those that nest above ground, some make nests in thick grass, while others make nests in bird boxes and in trees.

Bumble bee nests are quite small, as they house only around 400 bumble bees (as opposed to a honey bee hive with a colony of 50,000 bees). At the end of the summer, if the nest has been successful in rearing new queens, they will leave the nest to mate and then go on to hibernate somewhere in the soil – ready to emerge the following spring to start their own colony. The original queen and the rest of the bees die as cold weather approaches.

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Blueberry Stem Galls

3-29-17 blueberry stem gall IMG_7405Up to a dozen tiny black wasps (Hemadas nubilipennis) will emerge from this gall in the spring, around the time when blueberry bushes are flowering. After mating, the female wasp lays her eggs under the surface of the blueberry stems. Once she has completed her egg-laying, she climbs to the tip of the shoot and repeatedly stabs it, preventing further growth.

The plant reacts to the wasp’s egg-laying by forming a kidney-shaped gall. The majority of galls (up to 70%) are formed on stems within the leaf litter. These galls can be up to an inch in diameter, and they contain many developing larvae that feed on the walls of the gall and grow during the summer, overwinter as larvae, pupate inside the gall in the spring, and then emerge as adults when the blueberry bushes are in bloom in late May and early June. The adults are almost entirely females.

If a blueberry bush has many galls, it can be problematic.  A branch possessing a blueberry stem gall will not produce flower buds, and no flowers means no blueberries.

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Carpenter Bees Hibernating

email-carpenter bee holes IMG_1408If your home, shed or barn has weathered, unpainted wood and is riddled with ½”-diameter, perfectly round holes, there is a chance that carpenter bees are hibernating in them. Carpenter bees resemble bumblebees in both size and appearance (a carpenter bee has very few hairs on the top of its abdomen, which appears black and shiny, whereas bumble bee abdomens are often yellow and hairy), but they are not social insects. Instead of having a common nest in which they live and raise their young, carpenter bees drill  holes in wooden structures or trees inside of which they chew tunnels that contain six to eight brood chambers for their young. After creating the chambers, the female carpenter bee places a portion of “bee bread” (a mixture of pollen and regurgitated nectar) in each one. On top of each pile of food she lays an egg and then seals off the chamber. The larvae eat and grow, pupate and emerge as adult bees in late summer. At this point they feed on nectar, pollinating a wide variety of flowers before they return to their tunnels to over-winter.

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Female Black and Yellow Mud Dauber Wasps Making Cells & Laying Eggs

8-19-16  mud dauber 028If 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.

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Broad-leaved Helleborine Dispersing Pollen

8-10-16  helleborine pollinia 021Having 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.

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Cellophane Bees Emerging & Mating

4-20-16  cellophane bee  205Cellophane 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.

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