Friday, June 19, 2015

Ramble Report June 18 2015



Today's report was written by Dale Hoyt. The photos that appear in this blog are taken by Don Hunter; you can see all the photos Don took of today's Ramble here.

Announcement: Our resident poet, Bob Ambrose told us about a poetry reading and book signing at Avid Bookstore this Saturday, June 20 at 6:30 - 7:30. Three poets will read their work: Clela Reed, Bob Ambrose and Gene Bianchi. Click here for more information.

Twenty five ramblers met on this muggy morning, all eager to immerse themselves in the world of pollinators.

Today's reading: Catherine read an excerpt from Barbara Kingsolver's book, Small Wonders, about a hummingbird building a nest:

In the slender shoulders of the myrtle tree outside my kitchen window, a hummingbird built her nest. It was in April, the sexiest month, season of bud-burst and courtship displays, though I was at the sink washing breakfast dishes and missing the party, or so you might think. Then my eye caught a flicker of motion outside, and there she was, hovering uncertainly. She held in the tip of her beak a wisp of wadded spider web so tiny I wasn't even sure it was there, until she carefully smoodged it onto the branch. She vanished then, but in less than a minute she was back with another tiny white tuft that she stuck on top of the first. For more than an hour she returned again and again, increasingly confident of her mission, building up by infinitesimal degrees a whitish lump on the branch-and leaving me plumb in awe of the supply of spider webbing on the face of the land.
I stayed at my post, washing everything I could find, while my friend did her own housework out there. When the lump had grown big enough – when some genetic trigger in her small brain said, "Now, that will do "-she stopped gathering and sat down on her little tuffet, waggling her wings and tiny rounded under- belly to shape the blob into a cup that would easily have fit inside my cupped hand. Then she hovered up to inspect it from this side and that, settled and waddled with greater fervor, hovered and appraised some more, and dashed off again. She began now to return with fine filaments of shredded bark, which she wove into the webbing along with some dry leaflets and a slap-dab or two of lichen pressed onto the outside for curb appeal. When she had made of all this a perfect, symmetrical cup, she did the most surprising thing of all: She sat on it, stretched herself forward, extended the unbelievable length of her tongue, and licked her new nest in a long upward stroke from bottom to rim. Then she rotated herself a minute degree, leaned forward, and licked again. I watched her go all the way around, licking the entire nest in a slow rotation that took ten minutes to complete and ended precisely back at her starting point. Passed down from hummingbird great-grandmothers immemorial, a spectacular genetic map in her mind had instructed her at every step, from snipping out with her beak the first spiderweb tuft to laying down whatever salivary secretion was needed to accrete and finalize her essential creation. Then, suddenly, that was that. Her busy urgency vanished, and she settled in for the long stillness of laying and incubation.

Because the focus of today's ramble was on pollinators I thought it was appropriate to mention the results of a study on Chinese privet removal done here at the State Botanical Garden (and also at Sandy Creek Nature Center). In 2005 James Hanula and Scott Horn of the USDA Forest Service Southern Research Station here in Athens, used two methods to remove privet from areas next to the White trail along the river. Regular ramblers will recall reading the signage about the project. Hanula and Horn compared two types of privet removal: mulching with a track-mounted mulching machine or chainsaw felling. In the following two years they sampled the bees and butterflies in the two privet removal areas as well as control areas (those without privet removal) to see if there was any effect of privet removal or removal method. I read an excerpt from their published paper (Hanula, J. & S. Horn, Insect Conservation and Diversity (2011), vol. 4, pp. 275-283):

We caught 119 species of bees during the study. A total of 2510 bees were caught in 2006 and 4585 in 2007. More bees were caught in 2007 because the desired future condition plots were sampled that year in addition to the other plots, and bee abundance on privet removal plots was higher in 2007 than in 2006.  . . .  Privet shrub removal, regardless of method. resulted in three times as many bee species on removal plots compared with untreated control plots the first summer following removal. Removal plots had approximately 30 bee species per plot while untreated controls had approximately nine species per plot. Pan traps on plots in which the privet was mulched captured an average of 418 bees. which was more than 10 times as many bees as untreated plots (35 bees per plot). Traps on mulched plots also caught more bees than traps on plots where the privet was felled. Privet shrub removal resulted in higher bee diversity, but lower evenness* than control plots.

(*The reference to "lower evenness" refers to a measure of how the numbers of individuals collected are divided up into species. For example, suppose you collected 20 individual bees that were assigned to 10 species. If each species was represented by 2 specimens that would be an even distribution; all 10 species are equally abundant. On the other hand, if there were 11 individuals of one species and only 1 individual of the other 9, that would be a very uneven distribution.)

Today’s route:  Leaving the arbor, we made our way down the path past the Southern prairie garden and across the Flower Bridge into the International Garden.  From the bottlebrush buckeye, we wound our way along the path, bearing left at the Big Rock but missing the Pitcher Plant Mountain Bog and moving into the Herb and Physic Garden and on to the Heritage Garden.  From here, we ventured briefly into the Flower Garden before returning back through the Heritage and Herb and Physic Gardens, where we took the route through the International Garden closest to the Conservatory and then back to the arbor.

There were a lot of questions today about various aspects of bee biology and other flower visitors, so I thought I'd answer them all here in one place. 

Is there a big risk of getting stung? When bees are visiting flowers they are intent on only two things: gathering nectar and/or pollen. They will ignore you unless you hit or try to restrain them. Rapid motions may frighten them, but their response will be to fly away, not to sting. So get up close and listen to the buzz!

Will all bees sting? Only the female bee can sting. This is because the stinger is actually a modified ovipositor (ovipositor = egg layer), which only females have. There is a catch, though: most of the bees collecting nectar and pollen are females, so most bees you encounter on flowers are capable of stinging. Bees vary considerably in size, from the large carpenter bees and bumble bees down to the tiny solitary bees that nest in grass stems. Most of these smallest bees are not aggressive and would not sting unless restrained. I have watched tiny sweat bees sponging up perspiration on my hands and arms and never been stung, but once I unwittingly bent an arm and squeezed a sweat bee and received a mild sting.

What are solitary bees? Almost everyone thinks of all bees as being like honey bees: inhabiting a hive with hundreds or thousands of worker bees and a queen, collectively raising the queen's young (their sisters) and making honey. But the social bees only make up a few percentage of bees. And many social bee colonies (like bumble bees) are very small and only last for one year. Most bees are solitary, meaning that a single, fertilized female builds a nest by herself, provisions it by herself with pollen and nectar she collects, lays one or more eggs, and then seals up the nest with her developing offspring and abandons them to start another nest. At the end of the season she usually dies.

How can you tell bumble bees, honey bees and carpenter bees apart? The easiest way
Bumble bee
to distinguish a bumble bee from a carpenter bee is to look at the abdomen. Bumble bees are very hairy (fuzzy) all over, including
Carpenter bee
the abdomen, whereas carpenter bees have dark, shiny, nearly hairless abdomens. Many bumble bees will have yellow markings on their abdomen, entire segments may be colored or just parts of some segments, but the fuzziness is the best feature. Honeybees are smaller than the carpenter bees or bumble bees, but some bumble bees can be the same size as a honey bee. But honey bees
Honey bee with pollen basket on legs
have a smooth abdomen. In addition, the last few segments of a honeybee's abdomen have alternating black and orange-tan colored rings. Lastly, honey bees and bumble bees will usually be carrying clumps of pollen on their hind legs. Carpenter bees do not have pollen baskets on their legs. Sometimes bees visit flowers just for the nectar, in which case they will not have pollen on their legs, so this is not always a reliable means of identification. 

Why do bees collect pollen? Bees are vegetarian wasps! The pollen is food for the developing young. Pollen is very nutritious; it has a lot of protein which is necessary for the growth of bee larvae. The nectar is used to fuel the flight muscles and also to make a kind of bee bread – pollen moistened with a little sweet nectar to make a cake. Yum! Yum!

Are carpenter bees social? No. The large carpenter bee is a solitary bee. Many people first experience carpenter bees when they begin to chew holes in their home's wood trim or siding. The females excavate tunnels in unprotected wood and then provision the far end of the tunnel with a pollen-nectar mixture. When sufficient pollen has been collected the female lays an egg on the pollen mass and then seals the chamber with chewed wood fibers. She then begins to provision another chamber, building it right in front of the one she just finished. This is repeated until the tunnel is filled with developing bee larvae, each in its own walled off chamber. The female may excavate more tunnels but by the end of fall she dies. Meanwhile her young feed on the pollen/nectar mixture she has provided for them, molt into their pupal stage and overwinter as pupae. The following spring the pupae metamorphose into adult carpenter bees. The bee in the last chamber is the first one out and these earliest emergers are all males. They fly about, looking for other carpenter bee nests, waiting for females to emerge. It's a sure sign of spring when you walk outside and a large male carpenter bee hovers in front of you. He's just trying to determine if there are any potential mates there. After mating the newly fertilized females begin the cycle again. Some will reuse the nest chambers their mother built and others will begin to excavate new tunnels. How is it possible that the last eggs laid in the nest are all male? In ants, bees and wasps sex is determined by whether an egg is fertilized or not. Fertilized eggs develop into females; unfertilized eggs develop into males. So the mother carpenter bee is careful to fertilize all the eggs she lays early on while the nest is mostly empty. As the season progresses and nest fills she switches over to laying only unfertilized eggs. If she laid them early her sons would have to wait to emerge from the nest only to discover that all the females were already mated. 

Are all solitary bees like carpenter bees? In broad outline, yes. They differ in the material they construct their nest in, though. Some dig tunnels in the soil (mining bees), others excavate nests in broken twigs or plant stems (sweat bees). In some solitary bees the chambers in which the larvae develop are not linearly arranged as they are in carpenter bee. Instead they are side chambers off a main tunnel.

Why are bees on one kind of flower and not another? Flower selection in bees is dependent on many factors. If the bee is social, like the honey bee, they may have been pointed to a specific source by other bees in their hive. If a bee is solitary it may have learned through trial and error to favor certain types of flowers that match its tongue length, for example. Or had lots of pollen or lots of nectar. Different bees may be foraging for pollen and not nectar and vice versa. Bees also learn to handle specific flowers and may have a preference for those they have previous experience with. Put yourself in a bee's place. How do you find nectar when there is such a bewildering variety of flower shapes and sizes? Most insects that have been studied learn from experience. Their first attempts at gathering nectar are clumsy, but they gradually improve. An analogous situation: if you have a fast food restaurant that you favor, try going to one that you don't usually patronize. You'll spend more time looking at an unfamiliar menu with unfamiliar names before you get to place your order. That's like what a bee is faced with when it is choosing between, say, clover and mint. Do you want the Whopper or the Big Boy?

How can you tell the sex of a bee? This is hard, because there aren't any very many hard a fast rules. Males of honey bees are produced periodically throughout the season whenever the hive swarms and produces a new queen. In bumble bees the queen dies at the end of the season and she produces males toward the end of her life. So you will find male bumble bees in late summer, but almost all females in early spring. Male bees have larger eyes that females (they need to be able to find virgin females flying through the air and bigger eyes help). If you get familiar with bees you will be able to spot the larger eyes and impress your friends by scooping the males up with your bare hands.

What insects look like bees but aren't? Some flies resemble bees, at least superficially.
Hover fly on Bergamot (Monarda)
Hover flies, which are true flies in the family Syrphidae, often mimic the color patterns of bees with abdomens that have rings of alternating orange or yellow and black. But their behavior gives them away: they can hover motionless, except for their wings, in front of a flower. Bees can't do this. Another clue: hover flies are not hairy like a bee is. There is another type of fly in the family Bombyliidae that resembles a bee with a "needle" projecting from its front end. This is a bee fly and they are fuzzy and can hover like a hover fly. The "needle" is actually a tongue that can be inserted into a flower and used to sip up nectar while the bee fly is hovering. If you spend a little time studying the insects that associate with flowers you will gradually become able to see these differences with experience.

Do bees die if they sting you? In worker honey bees the stinger has barbs and gets stuck in your skin. When the bee that stings you flies away the sting remains in your skin with the venom sack attached, as well as other little parts of the bees anatomy. That bee cannot sting again and it will die from its injuries. But other bees do not have barbed stingers and they can sting multiple times. By the way, if you are stung by a honey bee it is best to scrape the sting out of your skin with something like a knife blade. Pinching it to pull it out only squeezes more venom out the attached venom sack, making the sting last longer and hurt more.

Are honey bees native to the US? No. All our honey bees were originally introduced by European colonists. Since their introduction they have become naturalized. Both feral and domesticated honey bees compete with our native bees for nectar and pollen and probably have contributed to the general decline in native bee numbers.

In the International garden we stopped to examine all the insects that were busy on the
Sweat bee with pollen baskets
numerous flowers on the Bottlebrush buckeye. Many of these were tiny bees that are difficult, at least for me, to identify. Some were metallic green and/or copper in color and it is likely that these are some kind of sweat bee. In the photo to the left you can see this tiny, metallic bee with the orange buckeye pollen stuffed into the pollen baskets on two legs. The sweat bee is a solitary bee that nests in hollow twigs or the stems of grasses. 
The Bottlebrush buckeye has numerous panicles containing up to a hundred or more flowers each. Each flower has 4-6 stamens that project far beyond the petals. The stamens are literally crawling with small bees stuffing the pollen from the anthers into their pollen baskets. This leads to a question: are these tiny bees pollinating the flowers or are they just stealing pollen? To be a pollinator an insect not only needs to pick up pollen, but it needs to carry that pollen to the female part of a flower, the pistil. More specifically, it needs to deposit the pollen on the stigma of the pistil. The insect doesn't need to be aware that it is doing this, it just needs to brush against the stigma to deposit some of the pollen adhering to its body. So the question we asked ourselves was: are these bees likely to blunder into the stigma? But when Hugh and I
Bottlebrush buckeye inflorescence
looked for pistils in the flowers we couldn't find any! Something interesting was going on here and it would take a little research to find out what it was. It turns out that the Bottlebrush buckeye is what botanists call andromonoecious, a fancy word that means that each plant carries a mixture of flowers that are complete and flowers that have
only stamens. (A complete flower has both stamens and pistil, i.e., both male and female parts.) Furthermore, this plant has, on average, only around 4-5% complete flowers, so out of every thousand flowers only about 50 are capable of producing seed. Can the tiny bees do the job? It seems unlikely that they would be effective pollinators since they spend most of their time hanging onto the anthers. But a recent study suggests a different, more likely pollinator. The Flame azalea has a flower that is similar to the Bottlebrush buckeye in that it's stamen stick out way beyond the petals and the pistil does the same. The principal pollinator of the Flame azalea is the Tiger Swallowtail butterfly. It transfers pollen from stamens to the pistil with its wings!! Here's how: when swallowtails get nectar from flowers they hover in front of the flower with their wings flapping. The flapping wings touch the anthers and get showered with pollen. They also come in contact with the stigma of the flower and subsequent flowers that the butterfly visits. So the pollen that adheres to the wings inadvertently gets transferred to the female structures of the next flower the butterfly visits. If it works this way for the Flame azalea it might work the same way for the Bottlebrush buckeye. We'll have to watch for swallowtails on our future rambles.

Bee condominiums: At one spot in the garden there is a small "house" that contains an
A bee "condominium"
array of tubes as nest sites for the use of solitary bees. These smaller bees that use these tubes are called Orchard bees or Mining bees. Orchard bees because they are effective pollinators in fruit orchards or Mining bees because they seal their nest with mud that they collect from the ground. Each tube contains several bee larvae in their individual, mud-delimited compartments. The mother bee keeps filling the tube until it can hold no more of her babies. Then she seals the end. At the end of the season the female will die and her children with emerge the following spring, chewing their way out of their tubular homes.

Nectar robbing: Some bees find it difficult to obtain nectar from some flowers. They might not have tongues long enough to get to where the nectar is. But why pass up a tasty meal when all you have to do is go through the back door? That is what this carpenter bee is doing -- it is biting a hole in the base of the flower and removing the nectar. This bypasses the mechanism the plant has for dispersing pollen and getting pollinated so the bee really is a thief.

Nectar robbing carpenter bee

We always come across things we aren't looking for or don't expect to find and today was no exception. Here is a young praying mantis that Ronnie found, followed by a poem Silvio remembered from his childhood.
Praying Mantis
Praying Mantis
From whence arrived the praying mantis?
From outer space, or lost Atlantis?
I glimpse the grim, green metal mug
That masks this pseudo-saintly bug,
Orthopterous, also carnivorous,
And faintly whisper, Lord deliver us.
—Ogden Nash, from Custard and Company


And, last, we leave you with this exotic looking caterpillar of the White-marked tussock moth:
White-marked tussock moth caterpillar



It was getting hot so we hot-footed it inside the visitor's center for some cool air and conversation over beverages at Donderos'.

SUMMARY OF OBSERVED SPECIES:
Wild bergamot, several colors
Monarda fistulosa
Hover fly (several)
Family Syrphidae
Crimson bee balm
Monarda didyma
Bottlebrush buckeye
Aesculus parviflora
Numerous bees and flies on buckeye

Wild quinine
Parthenium integrifolium
Culver’s root
Veronicastrum virginicum
Honey bee
Apis mellifera
Rattlesnake master
Eryngium yuccifolium
Chinese balloon flower
Platycodon grandiflorus
High bush blueberry bush
Vaccinium elliottii
American bumble bee
Bombus pennsylvanicus
Yellow and black bee on catnip
Unidentified
Leaf cutter bee
Family Megachilidae
Paper wasp
Polistes sp.
Eastern carpenter bee
Xylocopa virginica
Bee fly
Family Bombyliidae
Orchard mason bee
Osmia lignaria
Praying mantis
Order Mantodea
Betony
Stachys officinalis
Ruby throated hummingbird
Archilochus colubris
White-marked tussock moth caterpillar
Orgyia leucostigma

2 comments:

  1. Thanks, Dale. It's great to hear that privet removal led to an large increase in the numbers and diversity of pollinators on the USDA's research plots at the Bot Garden. I'd like to add that It is important to understand the method of privet removal that was used in this research. The description below (" Hanula and Horn compared two types of privet removal: mulching with a track-mounted mulching machine or chainsaw felling."), is incomplete and may lead readers to conclude that use of either the mowing/mulching machine or chainsaw felling alone are effective methods for privet removal. Herbicide was used in both research plots. Without the use of herbicide, the dominance of privet on site would likely have continued becasue the roots and stumps would have certainly re-sprouted and grown vigorously. In the study's mowing/mulching method, herbicide was applied some months later to the foliage after the privet roots re-sprouted. In the chainsaw method, an herbicide concentrate was applied to the freshly-cut stumps.
    For anyone wishing to eliminate privet or other invasive shrubs from their backyards or elsewhere, I would recommend the simple and effective "cut-stump treatment." Cut the stump near ground level and use a spray bottle or other applicator to immediately apply a glyphosate concentrate solution (anywhere from a 20 to 40% mixture will do the job) to the cut surface. Glyphosate is the active ingredient in round-up but is widely available from different brands of weed killers. Glyphosate is not active in the soil and breaks down quickly. Glyphosate is not unsafe for the environment and is of extremely low toxicity to animal life, including bees!
    Gary

    ReplyDelete
    Replies
    1. You're right, of course, Gary. I didn't include the details of the privet removal because my focus was on the effect on the bee fauna when privet was reduced, not on the best method of privet removal. I didn't want to get into the further details of the treatment. Thank you for including the additional information about the best method(s) for getting rid of this pernicious invader.

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