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Bumblebees Mating

The adult male bumblebee has only one function in life and that is to mate.  However, research shows that only one out of seven males are successful in this endeavor.  When mating does take place, it is more complex than one might imagine.

In most species, the male bumblebees fly in a circuit depositing a queen-attracting scent (pheromone) from a gland in their head onto vegetation and prominent structures such as trees and rocks.  This usually takes place in the morning, and if it rains, the scent is replaced.  The males then patrol the area, with each species of bee flying at a specific height. Once a (virgin) queen has been attracted, mating takes place on the ground or vegetation, and lasts anywhere from 10 to 80 minutes.  After the male’s sperm has been deposited he inserts a genital plug in the queen which, when hardened, prevents the sperm of other males from entering her for up to three days.  (Photo by Heather Thompson: queen bumblebee with several smaller male suitors)

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Bald-faced Hornet Queens Laying Specialized Eggs

A Bald-faced Hornet colony begins in the spring when a queen emerges from winter hibernation. The queen builds a small nest, creates a few brood cells within the nest, deposits eggs in them and feeds the larvae when they hatch.  These larvae are female workers — they will continue the nest building, food collection, feeding the larvae and protecting the nest while the queen concentrates on laying eggs.

During the summer the colony (and size of the nest) grows until there are between 100 to 400 workers. Toward the end of the summer the queen lays two special types of eggs. The first will be, like the workers’ eggs, fertilized eggs that will develop into females, but these females will be fertile (and develop into queens). The second group of eggs will be unfertilized eggs. These eggs will develop into fertile males. The maturation and emergence of the new queens and the fertile males marks the end of the functioning of the colony. At this point the workers are not replaced and die out. The ruling queen, having served her purpose, also dies. The newly-emerged adults (queens and fertilized males) leave the nest, mate, and the fertilized queens overwinter and begin their colony cycle all over again in the following spring.  Some small nests complete their cycle by mid-September, while some large nests are still going strong until the cold kills the larvae in late November.

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Bumblebees Active On Cool Mornings

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There is a reason why we often see bumblebees before we see honey bees in the early spring. It’s a matter of 5 degrees Fahrenheit. Bumblebees will fly when the air temperature is as low as 50°F. and sometimes lower. Honey bees cannot fly if it’s colder than 55°F.

Even though they can fly at 50°F., bumblebees cannot take off unless their flight muscles are above 86°F. and they must keep the temperature of their thorax between 86°F. and 104°F. In order to accomplish this, bumblebees uncouple their wing muscles so that the wings themselves do not move, and then use the muscles to shiver and raise their thorax temperature. (Photo: Tri-colored Bumblebee & Trailing Arbutus)

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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)

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)