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Hymenoptera

Yellow Jackets On A Bender

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At this time of year, yellow jackets, hornets and wasps take advantage of the plethora of fermented fruit that lies underneath fruit trees. Because the queen slows down the production of eggs in the fall, workers have time on their hands, as they have fewer larvae to collect food (chewed-up insects) for. Their life (but not the queen’s) is about to come to an end, and they go out in style. If you have observed these members of the Vespidae family acting more erratic, it may well be because they are drunk on hard cider. (Photo:  yellow jackets binging)

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Flight of the Bumblebee

bumblebee and turtlehead 049A4838If you examine plants that are still flowering this late in the season (such as asters, goldenrod and late-blooming turtlehead) early in the morning when it’s still quite cool or late in the day, many of the pollinators you see will be bumblebees, not honey bees. One reason for this is that they have different temperature tolerances for flight. You rarely see a honey bee when the temperature is below 57°F as they cannot fly when it is this cool. Bumblebees, however, are capable of flight when the air temperature is as low as 50°F.

Even so, bumblebees cannot take off unless their flight muscles are above 86°F; they maintain the temperature of their thorax (where wings and wing muscles are located) between 86°F and 104°F regardless of the ambient temperature. The way in which they raise the temperature of their thorax involves uncoupling their wing muscles so that the wings themselves do not move. They then use their wing muscles to shiver and raise the temperature of their thorax until it’s sufficiently warm enough for them to fly.

At rest a bumblebee’s body temperature will fall to that of its surroundings. If it is cool out, and the bumblebee wants to take flight, you can actually see its abdomen pumping to ventilate the flight muscles. An entomologist studying this phenomenon discovered that the rate of pumping can give an indication of the temperature of the bee. It ranges from around 1 pump per second when the bee is 86°F, to 6 pumps per second when it reaches 95°F.


Blue Mud Dauber Wasps Building Nests

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Yesterday’s Mystery Photo showed evidence of a Blue Mud Dauber Wasp (Chalybion californicum) scraping the mud with its mandibles as well as the resulting ball of mud it had formed to use as building material for its nest.  You can get a hint in this photograph of the iridescent blue wings that give this wasp its common name.

Mud dauber is a common name for solitary wasps that make individual nests for their eggs/brood with mud. There are many species of mud daubers, but most are between one and one-and-a-half inches long, black or metallic blue, and typically have a narrowing, or “thread-waist,” between their thorax and abdomen.

Most species of mud daubers, after making a small (1/4” diameter) tube nest out of mud or refurbishing an old nest, leave to forage for spiders. Once a spider has been located, the wasp stings and paralyzes it, but does not kill it (so as to prolong decomposition), carries it back to its nest, and repeats this process over and over until the nest is stuffed with living prey. The wasp then lays an egg in this mass of spiders and seals the nest with mud. The egg hatches and the wasp larva consumes the spiders as it grows. After pupating in the fall, the adult wasp emerges in the spring, mates and the cycle continues.

The reason that the ball of mud that the Blue Mud Dauber had formed was not taken back to the nest site as building material appears to be a small rootlet which anchors the ball to the ground, preventing the wasp from removing it.


Thread-waisted Wasps Provisioning Nests

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There are over 1,000 North American species of solitary hunting wasps. All of them prey on arthropods, which the female stings and paralyzes (but doesn’t kill so that they don’t begin to decompose immediately). Most solitary wasps specialize on a single type of prey, and many build highly characteristic burrow nests. Once the prey is stung, the wasp carries it back to her nest where she then lays a single egg and closes up the nest. The developing wasp larva feeds on the paralyzed prey, pupates and emerges as an adult wasp.

One group of solitary hunting wasps is referred to as thread-waisted wasps (family Sphecidae), due to their long, stalk-like waists. While most close up their nests (by kicking sand over the entrance) after stocking it with prey and laying an egg, some species close their nest with a pebble and return, remove the pebble, and periodically restock the nest with fresh caterpillars for the growing larva. (Photo by Mardie Holland: thread-waisted sphecid wasp with caterpillar prey)


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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