Bumblebee Season Finale

Bracketing the walkway to our front door, is a small collection of domesticated flora with showy blooms. Warm temperatures allowed these plants to thrive well into November. They continued to produce new flowers long after the blooms on native plants and disappeared. During the latter half of October, swarms of bumblebees moved in and made these plants home.

Things went well for the bumblebees until the overnight low temperature hit 26° F. Coleus, which I had allowed to flower and which turned out to be a favorite of the bumblebees, froze and was lost as a nectar source. A low of 19° F the next night put an end to the salvia and most of the zinnias.

That low temperature also proved to be too much for most of the bumblebees. The patio was littered with bodies Sunday morning. Bumblebees have the ability to warm their bodies by shivering, so they can survive some cold temperatures. Eventually, the temperatures get too cold or the bee just runs out of energy and it dies.

Most of the bodies had the classic tongue extended death repose. A check of the bodies show the bees all to be male. Bumblebee colonies are single-season affairs. The colony begins in the spring when a single fertile queen begins laying eggs and raising her brood. Near the end of summer, young queens and males leave the soon to collapse colony. The males spend their time drinking nectar and searching for queen bees with which to mate. Eventually, the queens hide themselves away in a safe place to spend the winter and the males are left with nothing to do but drink nectar and await the killing freeze.

The few bees that were left alive Sunday morning were found hanging from the flowers. They were all on the porch side of the flower planting where a little bit of warmth stored in the concrete and brick gave them a slight survival advantage. It’s typical behavior for these bees to just stop their activities as evenings begin to cool and spend the night on the flowers from which they were feeding.

When temperatures warm up, the bumblebees once again become active and continue feeding from where they left off the day before.  A temperature of 21° F Sunday night left no bees alive Monday morning.

As this video shows, after a cold night it takes the bees a little while to regain their coordination and function normally.

Flowering Shrubs

Two weeks ago we had snow on the ground.  Since then we’ve had several days that have reached 80 degrees and the plants are working hard to make up for lost time. I was out yesterday checking on the progress of the flowering shrubs.  Fragrant Sumac usually begins the show and attracts a wide variety of pollinators.  This year is a slightly different scenario.  The sumac is blooming later than usual and several other shrubs have developed competing blooms.

Redbud has reached its peak bloom.  I can’t remember ever seeing the Redbuds go so quickly from bare branch to full flower.

Viburnums are keeping pace with the others.  We haven’t had much in the way of cold nights to slow these guys down.

Sassafras seemed to go from bud to bloom in just a couple of days. 

Wild Plum is making a marvelous showing.  Development of fruit still depends on weather conditions yet to come.

Shrubs along this field edge are entering their third year without any competition from invasive exotics.  They are doing a nice job of filling in the holes left behind when the Autumn Olive and Multiflora Rose were removed.

Shrubs are a primary nectar source for many of the early butterflies and visiting the blooming shrubs is the easiest way to spot a few of the rarer butterfly species.  In a typical year the blooming periods of the various shrub species are slightly staggered.  This tends to concentrate the butterflies onto one species at a time.  With this year’s smorgasbord of blooms, the butterflies are more widely scattered.  Many of the flowering shrubs have now grown to a quite respectable height, so besides being spread out, the butterflies are high above my head.  This Henry’s Elfin is a species that deposits its eggs on the flowers of the Redbud.  I saw several high in the tops of the Redbuds, but none came within range of a decent photograph.

The most common small butterfly species is currently the Spring Azure.  I found these everywhere I walked, but they couldn’t manage to stay on a shrub flower long enough for me to get a photo.

This was the problem.  Juvenal’s Dusky Wings had claimed territories on every shrub around the edge of the field and were chasing away the Spring Azures whenever they came near.

Bumble Bees were taking advantage of the abundant flowers.  Princeton University Press just released the new Bumble Bees of North America Identification Guide and I thought I would do some work on Bumble Bee identification this summer.  The guide is full of great information, but it seems that many Bumble Bee species have a wide variation in color patterns and several common species share similar patterns, so simple visual observations may prove unsatisfactory for identification purposes.  I’ll give it a try anyhow.

Wingstem

Late August is a time of tall plants at Blue Jay Barrens. One of the most conspicuous is Wingstem, which can easily reach nine feet tall.  This year however, I’ve only found one plant that has been able to place its flowers above my head.

In a normal growing year, this view would have been blocked by towering Wingstem plants.  When the early drought was at its worst, the young plants stopped growing and stood for days with their leaves hanging limp along the stems.  The random rain showers restored them to vigor, but it was too late to put on any more height.

The display of flowers has been undiminished by the stress.  I would almost say that there were more flowers than normal, but it may just be that I’m unused to seeing them at this angle.  My normal view is from below.

Wingstem gets its name from the narrow projections running the length of the plant stalk. 

Long, pointed leaves line the full length of the stalk.  This aggressive native perennial uses height, shade and an expansive root system to maintain its place in the open field community.  It declines in extremely dry conditions, so it’s not likely to be found growing in extremely shallow soils. 

Some of the early flowers have already produced seeds.  Birds will claim most of these.  Finches in particular find Wingstem seeds to be especially desirable.

There won’t be any shortage of Wingstem seeds this year.  New buds are still forming, so flowers should continue to bloom for the next several weeks.

Many of the regular insect visitors seem to be absent this year.  I did find several of these Spotted Cucumber Beetles on the flowers.  It’s been several years since I’ve seen this species around here.

Ailanthus Webworm Moths have suddenly appeared in large numbers.  I was happy to learn that this moth feeds on several other deciduous trees besides Ailanthus.  The presence of the moths kept making me think that the invasive Ailanthus was somewhere nearby.  I know that Ailanthus will probably reach Blue Jay Barrens one day, but now I believe that it is actually farther away than I thought.

Bumblebees are the dominant flower visitors. Most were carrying full loads in the pollen baskets on their hind legs.  I doubt that these tight masses of pollen are effective at transferring pollen to the stigma of the flower.  Pollen carried on the bee’s body and leg hairs would more easily do the job of pollination.  Bumblebees are the most commonly seen large pollinators at Blue Jay Barrens.  They seem particularly abundant on large masses of flowers like those provided by the Wingstem.

Smooth Sumac Insects

Smooth Sumac, Rhus glabra, is just beginning to bloom.  I have an abundance of this plant along the trail leading up the hill behind the house.  It gets mowed about every three years and blooms heavily the second year after mowing.  The result is a massive display of blooms at just about eye level.  It’s just perfect for viewing visiting insects.

A flower head forms at the end of each branch.  Smooth Sumac is a common species that is recognized by its hairless stems.

The buzz of nectar eaters never ceases.  Bees, wasps, flies and beetles are frequent visitors of these flowers.  Hairstreak butterflies also make use of this nectar, but I have yet to see any of the hairstreak species this year.

Tachinid Flies were the noisiest of the various visitors.  Tachinids come in a variety of sizes and colors, but my preference is for these large types.

Tachinid larvae develop inside a living host, usually a specific insect species.  The adult flies are so numerous it’s almost impossible not to see them when you’re in the field.  Despite seeing thousands of adults, I’ve never seen a host insect containing a Tachinid larva.

This is a Yellow-collared Scape Moth.  I see this day flier on many different flower species that produce large flower heads.  The moth tends to take advantage of the flower cluster to partially hide itself while feeding.

 

Beetles abound in the flower cluster.  Most try to remain hidden among the small flowers.

I think this is some type of Soft Winged Flower Beetle.  I couldn’t tell if it was actually feeding inside the flower or searching for something on the outside.

Of course the little green bees were there.  I have yet to find a flower that doesn’t attract these bees.

I think sumacs are one of the preferred flowers of Bumblebees.  I always find an abundance of Bumblebees on these blooms.  I like to watch flowers because of the wide assortment of insects that they attract.  When they are busy feeding, insects are easy to approach and observe.  I’ll be spending a lot of time around the sumacs for the next week or so in hopes of seeing something new and unusual.

Onosmodium Insects

The larvae I was monitoring in the False Gromwell flowers have disappeared.  This doesn’t surprise me, because it is the normal conclusion whenever I try to follow caterpillar development in the wild.  Larvae often move to new parts of the plant as they grow and some even move to new plants, so there’s a chance they are alive and well in a different location.  They may have represented some small species and have already pupated.  I suspect they may have been eaten.  If I was able to find them, they should have been easy to discover by some caterpillar predator.

Those larvae may be gone, but something has deposited a bunch of new eggs in the flower whorls.  Maybe these are from the Onosmodium moth I’ve been looking for.

The Onosmodium plants are performing exceptionally well this year.  Many may top four feet once their flower stalks have completely extended.  While searching for my missing larvae, I took the time to examine a few other residents of the Onosmodium plant.

Some insects are found on a plant because of developmental requirements that can only be satisfied by a particular plant species.  Other insects are there just because the plant is a convenient resting place.  The host plant for this Elegant Grass-Veneer moth is grass, which is found in abundance in the prairie areas in which the Onosmodium grows.  To be fair, I have to admit that these moths were so abundant that they were probably resting on every plant in the area.  I couldn’t move without causing a few to take flight.

Small, black beetles were on all of the Onosmodium plants.  Most were doing like this fellow and struggling to negotiate the hairy stalks. 

Fireflies are another insect that just use the plant as a convenient resting structure.  Here is a Photinus species displaying one of the more comical insect faces.  This is a common species responsible for much of the low level flashing seen on summer evenings.

Bumblebees are common visitors to Onosmodium flowers.  Most were carrying impressive masses of pollen.  I often see bumblebees spend the night on nectar plants, so I’m not sure how often they actually return to the nest or how long it has taken to accumulate all of that pollen.

Southern Cloudy Wings were frequent visitors to the Onosmodium flowers.  Most nectar gathering insects tend to concentrate on a single plant species that offers an abundance of flowers.  When blooms fade on that plant species, the insect will begin visiting the next most abundant nectar source.  This habit benefits the plant by increasing the odds that flower visitors will be carrying the right pollen for that plant. The Southern Cloudy Wings consistently passed by other nectar producing species in order to reach the next patch of Onosmodium.

I found many insects in early developmental stages.  The best I could do in identifying this fellow was to determine it to be some type of Hemiptera that is not an aphid.  It was fairly fast moving and continued to evade my observation.

Small flies were particularly abundant on the Onosmodium.  This Rivellia species systematically traveled the plant leaf-by-leaf until I inadvertently scared it off.  It rarely paused and I have no idea what the object of the search may have been.

These two flies were doing a dance on the flower’s exerted style.  One fly would shift its body to one side and the other would match the maneuver.  The body shifts continued for a while and then one fly took off.  As with so many things I observe, I can’t explain the why behind the behavior, but that doesn’t make it any less fun to watch.