Oak Leaf Seed Galls Releasing Wasps
One of the most unusual looking insect galls, the Oak Leaf Seed Gall, is produced by a tiny gall wasp, Dryocosmus deciduus, on Black and Red Oaks. The leaves of these trees react to a wasp laying an egg on them by creating a unique swelling, or gall, around it. You can find clusters of up to 40 Oak Leaf Seed Galls at this time of year starting to burst open, releasing the adult wasps which have matured inside them.
Few records exist of galls, many of which are homes for developing young insects, being used as food for humans or for domestic animals but Oak Leaf Seed Galls, known as “black oak wheat” in Missouri and Arkansas, have been used to fatten cattle, sheep, pigs and chickens due to their high starch content.
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Blue Mud Dauber Wasps Building Nests
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
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)
Blueberry Stem Galls
Up 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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Female Black and Yellow Mud Dauber Wasps Making Cells & Laying Eggs
If you look closely at the ground directly in front of this female Black and Yellow Mud Dauber wasp you will see the clump of mud that she has collected and rolled into a ball with her mandibles. This lump of mud will be carried back to the nest site in the wasp’s mandibles, and then used as building material to mold a cell. After making the mud cell, the wasp then goes and locates spiders, stings them (paralyzing but not killing them) and brings them back to the cell, into which she packs them. When the cell is sufficiently stuffed with spiders, she lays an egg and seals the cell with more mud. She makes and fills several of these cells and typically covers all of them together with a final layer of mud. When the wasp egg in each cell hatches, the larva has living spiders to eat that haven’t decomposed, due to the fact that they are not dead. Eventually the larval wasp pupates and the adult wasp chews its way out of the cell.
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Broad-leaved Helleborine Dispersing Pollen
Having known since childhood that most insects have only one pair of antennae, imagine my surprise when I came upon a hornet on Queen Anne’s Lace that appeared to have two: a pair of slender, black antennae, and between them, a shorter pair of white ones. A bit of research revealed to me that in fact, these white “antennae” were actually the pollen sacs (pollinia) of an introduced and somewhat invasive orchid, Broad-leaved Helleborine (Epipactis helleborine).
Broad-leaved Helleborine is entirely dependent on insects to spread its pollen, especially wasps. It attracts them with nectar, which is said to have an alcoholic and narcotic effect which may help with the spreading of pollen, as an inebriated wasp is less likely to clean pollen off its body before leaving. Helleborine also produces a chemical which other plants produce and use to signal that they are being attacked by insects. It is used purely as a ruse by Helleborine, in order to attract wasps, Helleborine’s primary pollinators, who arrive to fend off other insects, and end up inadvertently collecting Helleborine’s pollinia.
Unlike the pollen of most plants, Helleborine’s pollen grains are so sticky that they cannot separate – thus, the entire package of pollen remains intact and is removed at one time. Wasps are capable of reaching the plant’s nectar without disturbing the pollinia, but cannot crawl out of the flower without striking against and detaching them and in so doing, getting them stuck to their heads. Can you find the pollinia in the insert photograph of a Broad-leaved Helleborine flower (which has not been visited by a wasp yet)?
Due to computer issues, Naturally Curious will resume posts next Tuesday, August 16.
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Bald-faced Hornet Nests No Longer Inhabited (if you live where there has been a hard frost)
If you research bald-faced hornet nests you will find that their average size is often compared to that of a football or basketball. The maximum size is said to be between 14 and 18 inches in diameter, and up to 23 or 24 inches in length. The pictured nest (which hung 20 feet above the roof of my house) measures 14 inches wide and 29 inches long – far larger than the average hornet nest!
This entire nest was built in roughly four months. It was started by a queen bald-faced hornet that, after emerging from hibernation this past spring, chewed some wood fiber, mixed it with her saliva and created a few brood cells surrounded by one or more paper “envelopes.” She laid an egg in each cell, and fed the hornet larvae insects which she first masticated into tiny bits. When the larvae pupated and emerged as adult workers, they assumed the duties of nest building, food collection, feeding the larvae and protecting the nest, while the queen continued laying eggs in horizontal tiers of cells. This ongoing activity produced a colony of anywhere from 100 to 400 workers by the end of the summer. Shortly before the first hard frost this fall, the queen left the colony and found a protected spot in which to spend the winter. When freezing temperatures arrived, the workers all died, leaving a nest that will never again be inhabited by bald-faced hornets. (Thanks to Nick Burnham, who ingeniously managed to collect the nest for me, and Gary Trachier for the photo.)
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Pigeon Tremex Horntails Laying Eggs
Horntails, also known as wood wasps, are non-stinging, wood-eating insects that lay their eggs deep within trees. Both male and female horntails have a pointed spine at the tip of their abdomen; females also have a long, slender ovipositor. (They get their name not from their spine or ovipositor, but from a knob (cornus) at the tip of their abdomen.)
Pigeon Tremex Horntails (Tremex columba) are active in late summer and early fall. A mated female inserts her ovipositor several inches into a dead or dying tree and lays an egg (where it is safe from most, but not all, predators). Along with the egg the adult horntail deposits some white rot fungus (Daedalea unicolor) which she stores in special abdominal glands. The fungus breaks down and softens the wood for the horntail larva to eat and is required for the successful development of the horntail. The larva typically begins consuming the soft, fungus-ridden wood around it, and then chews its way to the inner bark so as to provide a means of exiting the tree when it becomes an adult. The larva then returns to feed on inner wood. It completes its metamorphosis and emerges from the tree within a year as a winged adult horntail.
There is a parasitic wasp, the Giant Ichneumon Wasp (Megarhyssa macrurus), which possesses a long three-inch ovipositor capable of drilling into trees. There are several theories as to how this parasitic wasp detects the presence of horntail larvae deep within the tree. She may lay her antennae on the outside of a tree and pick up the vibrations of horntail larvae gnawing away in their wood chambers. Another theory proposes that the female wasp uses her antennae to smell the frass (droppings) of the horntail larva as well as the wood-softening fungus. Once she locates a horntail larva, the ichneumon wasp paralyzes it and then lays an egg on it. The ichneumon wasp larva feeds on the paralyzed horntail larva, consuming it completely within a couple of weeks. The ichneumon wasp then pupates and remains dormant under the bark until the following summer, when the adult emerges.
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Yellow Jackets Rebuilding Nest
From the size of the chunks of sod that were ripped out of the ground in order to access this subterranean yellow jacket (Vespula sp.) nest, one can deduce that a black bear, not a striped skunk or raccoon, was the nocturnal visitor. Usually there is little intact nest left after a bear tears it apart in an effort to find yellow jacket larvae, but in this case, a portion of the paper nest remained. Apparently undaunted, even with frost in the air (signaling the demise of all the yellow jackets except young, fertilized overwintering queens), the workers lost no time in rebuilding their nest. Twenty-four hours after their nest was torn apart, the colony of yellow jackets had diligently chewed enough wood fiber to have replaced much of it.
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Black and Yellow Mud Daubers Collecting Mud & Building Cells
There are many species of mud daubers — wasps that build mud cells in which they lay eggs and in which their larvae develop. The female Black and Yellow Mud Dauber gathers mud at the edge of a pond or puddle, rolls it into a ball, grasps it in her mandibles and flies it back to her nest site, a spot protected from rain, often on a man-made building. Here she constructs several mud cylindrical cells.
Like most wasps, mud daubers are predators, and they provision their mud cells with select spiders (including jumping spiders, crab spiders and orb weavers) which they locate, sting and paralyze before stuffing them into a cell. The female lays an egg amongst the spiders, so that when the egg hatches the emerging larva will have a supply of spiders (that haven’t decomposed, because they’re not dead) to eat. She seals the cell with mud, and repeats this process several times after which she covers the small group of cells with more mud. The Black and Yellow Mud Dauber larvae pupate in the fall, overwinter inside the cells and emerge as adult wasps the following spring.
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Woolly Oak Leaf Gall
Of the 2,000 kinds of galls found on North American plants, 800 different kinds form on oaks. One of these is the woolly oak leaf gall, produced by a tiny Cynipid wasp, Callirhytis lanata. This gall is usually attached to the mid-vein on the underside of an oak leaf, and looks like a ball of wool. It may be as large as three-fourths of an inch and is often bright pink or yellow in color, fading to light brown in the fall. Oak trees have lots of tannic acid in them (a defense which makes the tree unpalatable to herbivores), with the highest concentration found in oak galls. (The bitter taste is where the name “gall” originated.) It’s possible, since tannins are somewhat anti-microbial, high-tannin galls such as the woolly oak leaf gall may protect the larva against fungi and bacteria.
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Great Golden Digger Wasps Digging Nests & Provisioning Them with Food
The Great Golden Digger Wasp, Sphex ichneumoneus, is a solitary, predatory wasp whose hunting and nesting techniques are programmed and never vary. Having overwintered underground in a nest dug by its mother, the adult wasp emerges, often in August, and begins preparations for the next generation. She digs several nests in packed, sandy soil, using her mandibles to cut the earth. Emerging backwards from the ground with a lump of soil between her forelegs and head, she flips the soil with her forelegs beneath her body, scattering it to the sides with her hind legs. In this manner she excavates several cells off a central 4-6-inch deep tunnel.
The wasp seeks out prey — often a grasshopper, cicada or cricket – and then stings and paralyzes it. If the prey is small, she flies it directly to the nest. If prey is too large to transport aerially, the wasp will walk with it across the ground, dragging it by its antennae (see photo). She then drops the prey several inches from the nest hole. After crawling down into the nest for a brief inspection, she pulls the prey down into one of the cells while walking backwards. She then leaves to find another insect. When a cell contains paralyzed prey, the wasp lays an egg on the insect. The egg hatches within two or three days and the wasp larva begins eating the insect. Because the prey is not dead, decomposition is delayed, and the wasp larva’s food is relatively fresh. The developing wasps overwinter in the nest and emerge the following summer to begin the process all over again.
If you live near a sunny area of compacted clay and sand that has flower nectar for adults to feed on and crickets, grasshoppers and katydids for their larvae, you may well have a chance to observe this unique ritual. (Thanks to Marian Cawley for photo op.)
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Paper Wasp Queens Emerging From Hibernation
Paper wasps have annual colonies – only the young, fertilized queens overwinter, with the old queen, female workers and the males all perishing in the fall. The queens seek shelter behind tree bark, or in rotting logs or stumps, and emerge in the spring when temperatures rise and day length is increasing. Last year’s nest is not re-used – the queen mixes wood and plant fiber with her saliva, creating several waterproof paper cells into each of which she lays an egg — the start of her future labor force. Due to the lack of wildflowers (and therefore nectar) this early in the spring, queens rely on the sap from broken tree branches, as well as the sap found in drilled Yellow-bellied Sapsucker wells, for sustenance.
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Jewelweed Gall Midges
Abnormal plant growths called galls come in all sizes and shapes, are found on leaves, buds and stems, and are caused by a number of agents, including insects. A majority of insect galls are caused by the eggs and developing larvae of flies, wasps and midges. Jewelweed, or Touch-Me-Not (Impatiens capensis), has a very distinctive looking aborted bud gall that is produced by a midge (Schizomyia impatientis). While some galls provide shelter and food for a lone resident, the Jewelweed Gall Midge is colonial, and several orange larvae can be found residing in separate cavities within the gall. These midge larvae are now emerging and will overwinter as adults.
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Pelecinid Wasps Laying Eggs
The two-inch, skinny, black, shiny wasps with extremely long abdomens (five times the length of their bodies) that have been appearing on lawns lately are not the villains you may think. These female Pelecinid Wasps (males are much smaller and rarely seen) are actually beneficial, in that they greatly decrease the June Bug population. That long abdomen, or ovipositor, cannot sting you – it is strictly a mechanism for laying eggs. Its length is due to the fact that the wasp inserts its ovipositor deep into the ground in order to locate beetle larvae — specifically, June Bug beetle larvae. The wasp then lays one egg on each host beetle larva, and when the egg hatches, the wasp larva burrows into the host as it feeds on it, thereby killing the June Bug beetle larva. Eventually the wasp larva pupates and emerges above ground as an adult wasp the following summer – the phenomenon we are currently witnessing.
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Cerceris fumipennis: a biosurveillance tool for the emerald ash borer
While we’re more familiar with social wasps, such as paper wasps, yellow jackets and hornets, there are also parasitic and solitary wasps. Solitary wasps live alone (as their name implies), all the females (not just the queen) are fertile and they are predatory. Among them is a wasp, Cerceris fumipennis, which preys exclusively on the family of beetles (Buprestidae) to which the Emerald Ash Borer (EAB), the invasive beetle that’s threatening the ash tree population, belongs. After catching and paralyzing its prey, the wasp carries it back to her larvae in the nest she’s dug underground. A biosurveillance program exists which involves monitoring the prey that this species of wasp collects and brings back to the nest, in order to detect the presence of the Emerald Ash Borer in any given area. (This is how the EAB was first detected in Connecticut.) Pictured is a Cerceris fumipennis wasp with a Buprestid beetle (not an EAB) prey. (To become involved in Vermont’s citizen science biosurveillance program next summer, contact entomologist Trish Hanson of the Vermont Dept. of Forests, Parks and Recreation at Hanson.Trish@state.vt.us .)
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The Give and Take of Food in a Paper Wasp Nest
Like all adult wasps, bees, and ants, adult paper wasps are limited to liquid diets – they have no chewing mouthparts, and the passageway between their head and abdomen, where food is digested, is so narrow that pieces of food wouldn’t fit through it. Wasp larvae (the white grub-like organisms in the upper third of the pictured wasp nest cells) are able to eat a wider range of food, due to mouthparts and their body structure. Adult paper wasps capture and feed caterpillars and other insects to their larvae. The larvae then digest their food and produce saliva rich in nutrients. The adult wasp proceeds to scrape her abdomen across the nest, producing a vibration that signals to the larvae to release some of their carbohydrate-rich saliva which the adult then drinks. (Cells covered with white paper nest material contain wasp pupae.)
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Hibernating Queen Wasps
The queen is the only wasp in a colony to live through the winter (the others all die), and she usually does so in a sheltered spot such as a rotting log or under the loose bark of a tree (pictured). I wasn’t aware, until discovering this wasp, that queens actually chew a cavity in which to hibernate, but that appears to be the case in some instances. You can see the woody bits of fiber under the wasp that accumulated from her excavating the chamber. The cavity is roughly one inch long and ¼-inch deep. As a rule, hibernating queen wasps protect their wings and antennae by tucking them under their bodies. Some species produce glycerol, which acts as an antifreeze, while others allow ice to form around their cell walls and simply freeze solid. Most queen wasps die over the winter, primarily from predation by other insects and spiders, not the cold. (The pictured wasp had succumbed.) Warm winters are more likely to affect queens, as they emerge from hibernation too soon and starve due to lack of food.
A Great Christmas Present!
If you’re looking for a present for someone that will be used year round, year after year, Naturally Curious may just fit the bill. A relative, a friend, your child’s school teacher – it’s the gift that keeps on giving to both young and old!
One reader wrote, “This is a unique book as far as I know. I have several naturalists’ books covering Vermont and the Northeast, and have seen nothing of this breadth, covered to this depth. So much interesting information about birds, amphibians, mammals, insects, plants. This would be useful to those in the mid-Atlantic, New York, and even wider geographic regions. The author gives a month-by-month look at what’s going on in the natural world, and so much of the information would simply be moved forward or back a month in other regions, but would still be relevant because of the wide overlap of species. Very readable. Couldn’t put it down. I consider myself pretty knowledgeable about the natural world, but there was much that was new to me in this book. I would have loved to have this to use as a text when I was teaching. Suitable for a wide range of ages.”
In a recent email to me a parent wrote, “Naturally Curious is our five year old’s unqualified f-a-v-o-r-I-t-e book. He spends hours regularly returning to it to study it’s vivid pictures and have us read to him about all the different creatures. It is a ‘must have’ for any family with children living in New England…or for anyone that simply shares a love of the outdoors.”
I am a firm believer in fostering a love of nature in young children – the younger the better — but I admit that when I wrote Naturally Curious, I was writing it with adults in mind. It delights me no end to know that children don’t even need a grown-up middleman to enjoy it!
Wasps Still Flying
The lingering warm weather and the few remaining flowers (such as the mustard in the photograph) have allowed worker wasps to extend their lives this fall longer than many years, for once several hard frosts hit, they will die. Unlike honeybees, the queen of social wasp colonies lives only about a year, but that is longer than the workers. In the late summer the (old) queen stops laying eggs and the colony soon begins to decline. In the fall, mated female offspring of the queen seek overwintering sites such as rotting logs. In these protected spots they tuck their wings and antennae under their bodies, and hunker down for the winter. The remainder of the colony does not survive the winter. If predators such as spiders don’t kill the new queens, and if they don’t emerge early due to a warm winter and starve due to lack of food, the young queens begin building nests and laying eggs in the spring.
Common Aerial Yellowjackets
Common Aerial Yellowjackets derive their common name from the fact that their nests are often aerially constructed, unlike the underground yellowjackets we’re more familiar with. Being in the same genus, it’s not surprising that Bald-faced Hornets and Common Aerial Yellowjackets build nests that are almost identical. The nests of both species have two to six horizontally-arranged layers of comb (for eggs and larvae) inside several layers of protective paper envelopes. The easiest way to tell which species made a nest is to see if there are yellow (yellowjacket) or white ( hornet) markings on the residents. The yellowjackets on the outside of the nest in the photograph are all busy making paper-mache out of wood fiber and applying it to their nest in order to enlarge it.
Organ Pipe Mud Dauber Wasps
There are basically two groups of wasps: 1) social wasps, such as hornets, yellowjackets and paper wasps and 2) solitary wasps, species that live solitary lives and typically hunt prey for their larvae (the adults consume nectar). Mud daubers are a type of solitary wasp. Organ Pipe Mud Daubers builds cell out of mud in which they put prey (usually spiders) that they have stung and paralyzed, but not killed. They then lay an egg on top of the spiders, and seal the cell. After the egg hatches, the larval wasp consumes the still-fresh spiders, pupates, emerges as an adult wasp and chews its way out of the cell. In this picture a female Organ Pipe Mud Dauber wasp has collected a ball of mud and is applying it to the most recent cell she is making. The name “organ pipe” comes from the shape of the “pipes”, which consist of several cells, placed end-to-end, with the most recent cell at the bottom. (Notice the new, wet mud is darker in color.)
Naturally Curious with Mary Holland 
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