Bug o’the Week – Chimney Bee by Kate Redmond

Bug o’the Week
by Kate Redmond

Bug o’the Week Chimney Bee

Greetings, BugFans,

In late spring, BugFan Sara sent some “Who-is-this-and-what-is-it-doing??” pictures – small “bumble bees” were excavating the outer surface of a clay bread oven in her back yard (the BugLady gave Sara bonus points for having a clay bread oven in her back yard).  While she was mulling her answer, the BugLady found a reference to an Anthophora bee that is sometimes referred to as the Chimney or Turret bee.  That looked promising, and her hunch was confirmed by BugFan PJ.  Thanks, folks.

Family Apidae is a big umbrella in the bee world that includes Bumble, Cuckoo, Carpenter, Digger, and Honey bees – 1,000 species of them in North America and 5,000 species elsewhere.  The star of today’s show is in the tribe Anthophorini, the Digger bees (68 species in our area and 766 worldwide).  What they all have in common is a bumble-bee-ish appearance and the habit of most species of making nest tunnels in the soil.

Chimney bees (Anthophora abrupta) are solitary bees that can be found in woodlands and grasslands from Texas to the western Great Lakes to New England (solitary bees don’t have a central hive, a queen, or workers, and each female cares for her own brood).  They’re chunky, medium-sized bees (0.50” to 0.60” long) that can be distinguished from bumble bees by their color pattern – dark heads, pale, golden thoraxes, and dark abdomens, and by their very, hairy legs https://bugguide.net/node/view/55084/bgimage.  Males’ faces are light yellow https://bugguide.net/node/view/2133729/bgimage with hairs around the edges, earning them another common name – the Mustached mud bee.  For some great macro pictures, see https://www.fs.usda.gov/wildflowers/pollinators/pollinator-of-the-month/anthophora-abrupta.shtml and https://www.marylandbiodiversity.com/view/3137.       

In 1929, entomologist Phil Rau published a paper about Chimney bees in the journal Psyche. The BugLady is interspersing her information with excerpts from Rau’s paper, written back in the days when scientific writing allowed a more lyrical tone. 

“They are neither timid nor aggressive, but they certainly are self-reliant…how conspicuous they are as they noisily swing their ponderous bodies to and fro on the wing, arrive home and scramble into their burrows or come tumbling out headlong and dash off into the sunny fields, with all the exuberance of boys just out of school. They have none of the shy, stealthy ways of maneuvering, whereby some of the smaller and daintier varieties of bees and wasps hold their own in a competitive world.”

Chimney bees are generalist foragers that pollinate a wide array of wildflowers, and they’re also important pollinators of agricultural crops like cranberries, asparagus, tomatoes, blackberries, raspberries, and persimmons.  Their docility (if you handle one roughly, it’s more likely to bite than sting), home-body ways, and gregarious nesting make them interesting to researchers looking for potential large-scale pollinators.  Their long tongues https://bugguide.net/node/view/925446/bgimage allow them to reach the nectar in clover flowers. 

Rau recalled watching female Chimney bees licking rust on old fence wire.  A colleague speculated that while carnivorous insects glean minerals from the blood of their prey, the nectar-feeding Chimney bees may get minerals from rust.

Chimney bees are on the wing from late spring through late summer.  Males emerge almost a week before females, and they attract females by deploying pheromones that are carried in their moustaches!  Mating occurs on flowers (she mates once, but he may mate several times).  After they mate, the female looks for a spot to excavate a tunnel, often in a clay bank above a stream, usually in the same nest area she emerged from. 

Some solitary bees and wasps won’t tolerate the nearby nests of their sisters, but chimney bees prefer company. As Rau wrote, “Since they work in colonies, or more correctly remain to build on the site where they were born, the result is a very conspicuous village, sometimes a very crowded and busy town of these masonry turrets … At a busy season when many of these huge bees are bustling about with very audible hum and zip, the entire village with its many wonderful towers and industrious citizens form a spectacle which is in itself quite capable of overawing any but the most unemotional individual.

She employs a pretty unique construction method – she brings water or mud to her site and uses it to soften the clay so she can dig.  Each mouthful of dampened clay that she removes goes into building a chimney.  Rau describes it: “With a portion of the water they would wet the hard, yellow clay, remove a mouthful of it, back out and apply it to the last ring in the chimney. The bees would carry the mud under the thorax with the front pair of legs, while the two hind pairs furnished locomotion; as the bee backed out of the nest to the opening, the ball of mud was passed to the hind legs, and she now held her footing with the front legs while with hind legs she slapped the mud onto the last layer and with many active thumps with the tip of the abdomen, punched and beat it into shape. ‘Punched’ is really the right word correctly to describe the gesture.

Chimneys may be very short or up to 3” long, and they are oriented randomly.  No one knows exactly why she makes the chimney (other than that it’s a convenient way to dispose of the diggings) – researchers have guessed that it protects the tunnel from rain and blowing debris, that it helps with thermoregulation of the nest, that there is social significance for the community, and/or that (as Rau suspected) it helps her find her tunnel among all the others https://bugguide.net/node/view/1592323/bgimage.

Two factors may limit the building of chimneys – drought and a lack of clay in the nesting area.  Rau wrote that “A. abrupta made nests either with or without turrets, and the turret-making activities were directly correlated with water conditions. They required water in abundance, and when it was plentiful, so too were the turrets; in droughty years they struggled on with few and small or no turrets, and their nesting activities were much reduced.

She creates up to seven cells along the length of the tunnel (which is about 4” long), and here’s the magic part.  The walls of the tunnel and of each of the egg cells are lined with a waxy substance she makes in a gland called a Dufour’s gland.  The liquid made by the gland starts out clear, but it dries to a solid, waxy sheet that keeps moisture out of the tunnel and the cells.  She carries pollen and nectar into the cell and mixes them with liquid from the Dufour’s gland, injects an egg into the mix (which one researcher describes as a “soupy mass”) and seals the cell with clay.  The tunnel is covered with a clay plug when all the egg cells are provisioned.  A large, communal nest may contain 5,000 cells. 

Because the females don’t cap their tunnels when they are out looking for water, nectar and pollen, other females may try to take them over.  Writes Rau “Not infrequently an animated fight was to be seen between two females, one evidently trying to usurp the burrow that had been made by another, and often dead bees were found at the foot of the bank.

Frequently, however, the fights appeared quite alarming without proving fatal. One pollen-laden mother was seen backing out of her hole with the front leg of an intruder in her mandibles. The visitor showed no fight, but resisted with all her might; at the foot of the hole, every little gain that the rightful owner made was offset by the intruder pulling her back. At last the intruder lost her hold, and as they went tumbling to the ground they engaged in a pugnacious embrace.

After laying in the “soup” for five days, the egg hatches, and the larva feeds on the provisions and the cell lining.  They overwinter as pre-pupae, finish their metamorphosis in spring, and emerge from the tunnel.

And if all that weren’t enough, male Chimney bees climb up grass stems in the evening, grip them with their jaws, and sleep suspended by their mandibles https://bugguide.net/node/view/1801603/bgimage.  

Here’s Rau’s whole article: https://www.researchgate.net/publication/27371655_The_Biology_and_Behavior_of_Mining_Bees_Antitophora_Abrupta_and_Entechnia_Taurea

Ain’t Nature Grand!!

Kate Redmond, The BugLady

Bug of the Week archives:

Bug o’the Week – Gray Field Slug by Kate Redmond

Bug o’the Week
by Kate Redmond

Bug o’the Week Gray Field Slug

Salutations, BugFans,

The BugLady has been hitting all her favorite wetlands and taking pictures and editing pictures, and it’s July 4th, and she hasn’t quite gotten a crisp, new BOTW ready.  Since she has been a slug, writing-wise, she decided to rerun an episode from 2019 about slugs.  And besides, she is really tickled by the Scottish poem about slugs.

The BugLady found this impressive (1 ½” to 2”) slug climbing around on her cottage in early October.  It has been almost 11 years since we last considered slugs (time flies!).  For a quick Slugs 101 review, see https://uwm.edu/field-station/slug/.  Recent BugFans please note that slugs, while not insects, are fair game because BOTW uses the kindergarten definition of “bug,” not the entomological one.  Thanks (as always) to the very versatile BugFan Mike for help with the ID.

One reason that slugs seem so foreign to us is that they lack familiar landmarks like legs, wings, and body segments.  So, what are you looking at when you’re looking at a slug?  They lead with two pairs of retractable, regenerate-able, sensory tentacles.  The top (dorsal) pair, which is used for sight and smell, has eyespots at the tips (slugs can see light and dark and blurry shapes but can’t focus on images), and the lower pair is used for smell, taste and touch and to move food to the mouth.  These four appendages can be aimed in different directions simultaneously, but the lower pair is often pointed downwards in order to pick up cues from the slug’s substrate.  The mouth, complete with rasping “teeth,” is on the underside of the head. 

A saddle-shaped cover behind the tentacles, called the mantle, protects the slug’s innards; there’s an all-purpose opening on (almost always) the right side of the mantle called the pneumostome (one author calls it a “blowhole”), which has reproductive, excretory, and respiratory functions.  Beyond the mantle is the tail.  The muscular lower surface of a slug is the “foot;” its rhythmic undulation allows the slug to move, and it produces the infamous mucous/slime that keeps its body moist and “greases” its passage.  

 About that slime.  It’s a multipurpose substance that is both sticky and slippery, that aids in locomotion (some species use it as a bungee cord), that absorbs water, that protects slugs from bacteria and fungi, that leaves a trail for the amorous (and the carnivorous) to follow, and that discourages predators.  The BugLady found a tantalizing note about Hermann Lons, a German poet and malacologist (mollusc specialist) who discovered that slug slime tastes awful “in a particularly remarkable self-inflicted experiment” (about which she could find no further details).  Slug slime is also the strong yet flexible inspiration for researchers trying to develop a next-generation surgical adhesive.

Evaporation and slime production constantly rob slugs of their water reserves.  They can tolerate microclimates with a range of humidities as long as they can replenish liquid by eating and by absorbing water through their skin.  In hot, dry summer weather or when food is scarce, they will aestivate under debris or dirt, and they can fast for several months. 

To place slugs within their proper taxonomic sphere, they are in the very diverse Phylum Mollusca (octopi and squid, scallops and oysters, snails and slugs), in the Class Gastropoda (“belly-foot” – snails and slugs), and in a land slug family named Agriolimacidae.  

The GRAY FIELD/GARDEN SLUG (Derocerus reticulatum, aka Agriolimax reticulatum), one of about a dozen slug species in Wisconsin, is a European slug that’s described throughout both its historic and its more-recently-embraced ranges as a “synanthrope” – a species of plant or animal that lives in habitats modified by humans and that benefits from human association.  “Syn” means “with” and “anthropos” means “man,” and the term is applied equally to species we like (Golden retrievers) and species we don’t (Norway rats).  Across the Pond, it’s found in Western Europe and Africa; but it has hitchhiked (oh, so easily) pretty much around the world.  In North America, it’s found across southern Canada and the northern tier of states, plus a smattering of Central, Mid-Atlantic and Pacific Coast States.  It likes gardens, agricultural fields, roadsides, parks, and greenhouses. 

Slugs are hermaphrodites, which means that they have both male and female reproductive organs – an individual can be the fertilizer or the fertilizee’ (and they can self-fertilize), and all can lay eggs.  In our area, Gray field slugs reproduce in late summer and early fall – Mom-Dad meets Dad-Mom in an elaborate dance that involves slime, a chase, and the waving of the sacrobelum.  Eggs (as many as 700 in all) are laid in small bunches under stones and leaves and in crevices as fall rains soften the soil.  They generally overwinter as eggs, hatch in spring, mature by late summer, and die not long after laying eggs. 

Gray field slugs, notoriously, feed on the leaves and fruits of a wide range of agricultural and horticultural plantings and tree saplings, damaging leaves by rasping random holes in them.  They are also scavengers that eat dead, soft-bodied invertebrates like worms and other slugs. 

One of the questions that the BugLady always asks when she’s researching is “What does it eat?” and the next question is “What eats it?”  Members of the ground beetle family Carabidae are important predators of Gray field slugs both here and abroad.  This beauty, a (coincidentally) European ground beetle that is now established here and is a fellow synanthrope, is a slug connoisseur https://bugguide.net/node/view/632699/bgimage (business end https://bugguide.net/node/view/1566065/bgimage).  The Gray field slug, however, can detect the odor of its ground beetle stalkers with those sensory tentacles, and chemicals mimicking ground beetle scents may have a future in crop protection.  

When a ground beetle or other predator grabs a Gray field slug, the slug waves its tail back and forth and throws out lots of unpleasant, milky-colored slime (normally, its slime is clear).  The final trick in its playbook is to break off the tip of its tail and leave it in the mouth of its attacker as it scoots away.   

Gray field slugs operate within a home range where they revisit food plants and home sites.  The BugLady’s slug notwithstanding, they tend to be nocturnal, and Wikipedia tells us that they can travel as far as 40 feet in one night.   

Fun Slug Fact: when a slug ambulates across a copper surface, the copper reacts with chemicals in its slime and gives the slug a little shock.  

Another Fun Slug Fact: the defensive slime produced by the Australian Red triangle slug is so sticky that it can glue a pursuing frog to a branch.  For days. 

Final Fun Slug Fact: if you get slug slime on your person, it will be easier to remove if you let it dry and then rub it with a cloth than if you wash it with soap and water. 

The BugLady looked around for a nice, uplifting literary quote about slugs.  She couldn’t find any.  They’re all allude to slugs’ perceived negative attributes, like this “We have descended into the garden and caught three hundred slugs.  How I love the mixture of the beautiful and the squalid in gardening.  It makes it so lifelike” (Evelyn Underhill); and this, “Bob Dylan impresses me about as much as …well, I was gonna say a slug but I like slugs” (Don Van Vleit); and this, “It seems to me the worst of all the plagues is the slug, the snail without a shell. He is beyond description repulsive, a mass of sooty, shapeless slime, and he devours everything” (Cecelia Thaxter).  Oblivious to the fact that slugs are, yes, perfect (and that possibly they find us repugnant). 

Slugs in poetry?  The BugLady found this wonderful poem by George T. Watt; it’s dense, but lean into it and read it a few times http://www.scottishpoetrylibrary.org.uk/poem/slugs/ (Note – Ein Heldenleben – “A Hero’s Life,” is a work by Strauss). 

About slugs, Watt goes on to say that “Slugs haes trevelled awa on its ain journey, ye maun tak it whaur it’ll gang.”  

Words to live by.  

Kate Redmond, The BugLady

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