Weevil Watching
If you take a close look at the Black-eyed Susan blossoms that can be found in unmowed fields and roadsides this time of year, chances are good that you will find a tiny beetle called a weevil. A weevil’s mouthparts are formed into a long snout, with one antenna on either side of it. The snout is used not only for feeding but also for making cavities in buds, fruits, seeds, stems, and roots of plants, where eggs are laid. When the weevil larvae emerge, they feed within the plant.
There are 60,000 species of weevils, all of which are herbivorous and most of which are less than ¼ ” long. Most of those found on Black-eyed Susans appear to be feasting on pollen. Many weevils are pests of plants such as cotton, alfalfa and wheat. You may have even found them inside your house devouring your cereal or flour.
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Beavers Feeding Young
In summer Beavers spend considerable time on land searching for, cutting and bringing vegetation back to their young in the lodge. Their woody plant preference (they eat large amounts of herbaceous plants during the warmer months, but also some trees) tends towards the inner bark (cambium) of willow, aspen, maple, birch, cottonwood, beech, poplar, and alder trees. This beaver, however, has retrieved a Red Oak sapling for its offspring.
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Metamorphosis Clarification
I misworded part of the most recent post on caterpillar molting. For clarification purposes, both butterflies and moths undergo complete metamorphosis: egg, larva, pupa, adult. Butterfly pupae are inside a chrysalis, moths inside cocoons! A butterfly molts for the final time, revealing a chrysalis (containing a pupa). A moth caterpillar spins a cocoon before pupating inside it. (Note shed Monarch caterpillar skin/exoskeleton at top of chrysalis.)
Caterpillars Eating & Molting
The larval stage of a butterfly or moth is spent doing little but eating. Only as a caterpillar will these insects have chewing mouthparts, and they waste no time in using them. As they eat, caterpillars increase in size and their skin (exoskeleton) becomes tighter and tighter, as it doesn’t grow larger. The caterpillar grows a new, larger exoskeleton underneath the outer skin and then sheds, or molts, the old one. Most caterpillars molt five times. At first, the new exoskeleton is very soft and not very protective, but it soon hardens. The shed exoskeleton is often eaten before the caterpillar ingests more plant food.
There are names for the caterpillar’s stage of development in between each molt, called “instars.” When the caterpillar hatches from its egg, it is referred to as a “first instar” caterpillar. After its first molt, the caterpillar is referred to as a “second instar,” and so on up until the exoskeleton is shed for the final time, revealing the chrysalis (if it’s a butterfly).
The Monarch in the photograph is a very new 4th instar instar caterpillar (see antennae which haven’t hardened). It has shed three times. Its third exoskeleton (which it has just shed) is on the milkweed leaf behind the caterpillar. To see a real-time video of a Monarch molting go to https://www.youtube.com/watch?v=EbHyq3RwtxI.
(Thanks to Otis Brown for his keen eye in finding this Monarch caterpillar before it ate its just-molted skin. Also to Ba Rea ((www.basrelief.org) for her instar confirmation.)
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Predaceous Diving Beetles Seeking Prey
There is a family of water beetles, Dytiscidae, known as Predaceous Diving Beetles. As their name implies, these beetles are predatory. They don’t hesitate to attack prey larger than themselves, delivering a sharp bite with their jaws to small fish, tadpoles and frogs. They then immediately inject enzymes that digest the prey so that the juices can be ingested.
Predaceous Diving Beetle larvae, called “water tigers,” are also predators, grabbing prey with their pincer-like jaws. The larvae are elongated, flattened and can be 2 inches long. They hunt by holding still, waiting with jaws wide open, and then strike suddenly, clutching the prey tightly with their jaws. As with the adults, the pincers are hollow, enabling them to begin sucking the juices of their prey while grasping it. They are often seen when they come to the surface of the water to draw air into spiracles located at the hind end of the body.
Adult Predaceous Diving Beetles are collected by young girls in East Africa. It is believed that inducing the beetles to bite their nipples will stimulate breast growth. Having recently had my toe bitten by a Predaceous Diving Beetle, I can testify that this is not a practice that most females (or males) would enjoy. (Photo: Predaceous Diving Beetle with remains of prey)
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Red Elderberry Attracts Wildlife Year Round
The pollinated and fertilized white flowers of Red Elderberry (Sambucus racemosa) have recently developed into the red fruit for which this plant is named. Many people are familiar with its relative, Common Elderberry (S. canadensis), which produces dark purple fruit that is used to make jams, jellies, pies and elderberry wine. While Red Elderberry fruit can be used to make all of these, its raw berries are toxic. Red Elderberry’s popularity is greatest with pollinators, birds and four-footed mammals.
The cyanide-producing toxins in its flowers, (raw) fruit, stems, bark, leaves and roots do not seem to discourage wildlife’s attraction to Red Elderberry. The odor of its flowers, its nectar, and its highly nutritious pollen attract many ants, bees, wasps and flies. At least 50 species of songbirds eat the bright red fruits, including red-eyed vireos, ruffed grouse, song sparrows, gray catbirds, brown thrashers, and thrushes. Squirrels, mice, raccoons, and black bears also eat the fruit. Porcupines, mice and snowshoe hares eat the buds and bark in winter. The foliage is usually avoided by herbivores, although white-tailed deer and moose browse on it occasionally.
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Survival Through Mimicry: The Viceroy Butterfly
The survival of Viceroy butterflies in all of their life stages is significantly enhanced by mimicry. A Viceroy egg resembles a tiny plant gall. Both larva and pupa bear a striking resemblance to bird droppings. And the similarity of a Viceroy to a Monarch is well known. For years it was thought that this mimicry was Batesian in nature – a harmless organism (Viceroy) mimicking a poisonous (Monarch) or harmful one in order to avoid a mutual predator. However, recently it’s been discovered that the Viceroy butterfly is as unpalatable as the Monarch, which means that mimicry in its adult stage is technically Mullerian – both organisms are unpalatable/noxious and have similar warning mechanisms, such as the adult butterfly’s coloring.
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True Bugs
Although the term “bug” is commonly used to refer to just about any insect, there is a specific order of insects (Hemiptera) that are considered “true bugs” and allies. All insects in this order possess a syringe-like beak that they use to suck the liquefied contents out of plants or animals. Their lower lip forms a sheath that contains four blades. One pair of blades (mandibles) is for cutting and the other pair (maxillae) is for spitting and sucking. The maxillae combine to make a tube with two channels, one for sucking food up and the other for spitting saliva (containing enzymes that dissolve tissue) back into the food.
Some of the insect-eating true bugs may be familiar to you – assassin bugs, ambush bugs and damsel bugs (named for their diminutive size) are among them. Nabicula subcoleoptrata (pictured) is a common black, ant-like damsel bug known for its aggressive predation. Look for it in meadows, where it frequently preys on an introduced bug, the Meadow Plant Bug (Leptopterna dolabrata). In this photograph, it has successfully preyed upon and consumed a small larva, identity unknown.
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Lady Fern Spores Maturing
Ferns are non-flowering plants which reproduce by spores, not seeds, and have a vascular system that transports fluids (unlike mosses, algae and liverworts). Spores are typically located inside a capsule, or sporangium. In many species of ferns, clusters of sporangia, called sori, are borne on the underside or margins of their fronds. Often an indusium, or protective flap of tissue, covers each sorus, protecting the developing sporangia. If you like to be able to give a fern a name, you will find that the shapes and arrangement of sori are a valuable identification tool.
Northern Lady Fern, Athyrium filix-femina, is a fairly common fern found in moist woods, swamps, thickets and fields. It appears quite lacy and often grows in a somewhat circular cluster. There are two distinguishing characteristics which are particularly helpful in recognizing Lady Fern. One is its eyebrow-shaped sori. If you look on the underside of a spore-bearing frond you will find that each sori is slighted curved, or arched, like an eyebrow. The other diagnostic feature is the scattered thin, dark brown scales that are found on the stipe – the section of the fern’s stem between the ground and where the leafy frond begins.
This time of year, when the spores of many fern species are maturing, is a good time to learn the different ferns in the Northeast. There are many excellent field guides to ferns. One that you can easily tuck into your pocket is Lynne Levine’s Identifying Ferns the Easy Way.
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Common Loon Chicks Riding High
July on a lake occupied by nesting Common Loons is a birder’s slice of heaven. Eggs are hatching, day-old fluff balls are riding high on their parents’ backs, parents are busy catching and delivering small fish and crayfish to their chicks, and survival lessons are being given. Recently while watching a pair of two- or three-day-old chicks whose parents were off obtaining their offspring’s next meal I observed a juvenile Bald Eagle, known predator of Common Loon chicks, soaring overhead. Within a split second both loon chicks dove and stayed submerged long enough for the eagle to give up the ghost. Nature or nurture?
To see a related entertaining phenomenon, go to https://loonproject.org/2019/06/29/unlikely-allies/?fbclid=IwAR0po44dJaElcyYpqKqLwaz9A6gs7RxWfhJRkoB-QleC7sUGnjgElksR5G4.
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Monarch Butterfly Larvae Are Cannabalistic
The very first meal that a Monarch Butterfly caterpillar eats is its own eggshell. In order to hatch, it eats its way out of the egg, and then polishes off the remainder of the eggshell. It then starts to wander around the leaf and if it finds another Monarch egg, it will start to eat it.
Female Monarch Butterflies lay 300-500 eggs over two to five weeks of egg-laying. Normally, a Monarch only lays one egg at a time (on the underside of a tender, young milkweed leaf). It is fairly rare to find more than one egg on a leaf, or even on the same plant. After a female lays an egg, several seconds up to a minute goes by before she lays another egg (referred to as a refractory period). During this time she usually moves on and finds another milkweed plant on which to lay the next egg. This lapse of time between the laying of each egg probably evolved to discourage the laying of multiple eggs on one leaf and to encourage the dispersal of a female’s eggs on different milkweed plants so as to decrease the chances of cannibalism occurring.
According to Dr. Lincoln Brower, renowned Monarch entomologist, a cluster of Monarch eggs on any given milkweed leaf indicates that either milkweed is in short supply, or the female that laid the eggs is either sick, very old or she has been flying for a very long time and several eggs have matured.
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Second Edition of Naturally Curious Released
Nine years after the original edition of Naturally Curious came out, a second edition is being released. New photos have been added and updates have been made. I am delighted that it is still in print, especially because numerous schools and colleges have incorporated Naturally Curious into their curricula and I would love to see this practice continue. Thank you for purchasing a copy of the first edition – your endorsement is what made a second edition possible! A short “book trailer” video of the new edition can be seen here: https://www.youtube.com/watch?v=uFtGPjPWKv0 . If you are interested in purchasing a copy of the new edition, you can order directly from the publisher by clicking on the image of the cover on the Naturally Curious blog site, or you can order it from online bookstores.
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Bumble Bee-Mimicking Robber Flies
Robber flies are a special group of predatory flies that possess stout, spiny legs, a dense moustache of bristles on the front of the head (mystax) that protects the robber fly’s head when it encounters struggling or stinging prey, and three simple eyes in a depression between two large compound eyes.
Certain robber flies resemble bumble bees. The evolutionary advantages of a harmless organism mimicking a harmful organism (Batesian mimicry) include deterring predators that are fearful of stinging bees. In addition, it also makes it more likely that a potential prey insect will come closer to the bee mimic, thinking the “bee” is looking for nectar or pollen, not a meaty meal.
A quick way to distinguish a robber fly from a bumble bee is to look at the antennae and wings. Flies usually have short, stubby antennae; bees, including bumble bees, have “elbowed” antennae (an obvious joint). Flies have two wings, while bumble bees (and most other insects) have four. The pointed, stout proboscis, bearded face, fleshy feet and long, tapering abdomen of robber flies are also identifying characteristics. (Photo: Laphria thoracica piercing a click beetle between the beetle’s hardened outer wings (elytra) in order to inject enzymes which will eventually allow the robber fly to drink its prey.)
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Black Swallowtail Larvae Defending Themselves
Caterpillars, the larval stage of moths and butterflies, are very susceptible to predators (escaping quickly is not an option). Much of their energy in this stage is devoted to defense mechanisms to thwart would-be predators. A partial list of these defenses includes irritating bristles with detachable tips (Tussock Moths), toxic “breath” (Tobacco Hornworms, consumers of tomato plants, tobacco and other plants in the nightshade family, release toxic, bad-smelling nicotine), toxic bodies (Monarchs) and anti-coagulant venom (Giant Silkworm Moths).
Black Swallowtail (Papilio polyxenes) larvae defense mechanism strategies change as they develop. In early stages, or instars, they mimic bird droppings (not an appealing meal for most predators) and older larvae possess bright yellow-orange, horn-like organs behind the head known as osmeteria (see photo inset). When threatened, larvae rear up, extrude the osmeterium, and attempt to smear potential predators with a chemical repellent.
Black Swallowtail larvae are frequently sought after by parasitoids, which can locate their hosts by chemicals in the hosts’ feces (frass). To decrease their chances of being parasitized, Black Swallowtail larvae toss their fecal pellets away from themselves with their mandibles.
To learn much more about both moth and butterfly larvae, go to http://www.thecaterpillarlab.org.
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Pileated Woodpeckers Fledging
When your children start to get this feisty, it’s time for them to leave the nest!
Between three and a half and four weeks of age, Pileated Woodpecker nestlings fledge. Their flight feathers are about 75% of adult size when they depart. Some fledglings are capable of sustained flight when they leave the nest, while others may need several days before they can fly any distance.
Initially parents and siblings stay in the vicinity of the nest, but once the young can fly well, they follow adults everywhere. All the young may stay with both parents, or the parents may split up and each take some of the young. The fledglings will remain with their parents into September. (Photo: male Pileated Woodpecker nestling about to fledge while his father watches.) Much gratitude to Amber Jones and Dave Bliven for sharing their deck, their sweet dog Briggs and their magnificent view of this Pileated Woodpecker family with me.
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Pileated Woodpecker Parents Removing Fecal Sacs
Young birds defecate in little packages called fecal sacs. These structures serve several purposes, one being that having waste contained in a sac keeps the nest relatively clean. Often parents consume these sacs when their nestlings are small (when young the birds don’t completely digest the food they eat and fecal sacs may provide parents with a nutritional snack), but eventually the adults usually retrieve them and fly away from the nest before dropping them. (The young of some species of birds in open nests perch on the rim of the nest and defecate.) Two to five days before fledging, Pileated Woodpeckers stop removing their offsprings’ fecal sacs (perhaps as an incentive to depart the nest?).
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Pileated Woodpecker Parents Regurgitating
Nestling meals consist primarily of invertebrates. Adult Pileated Woodpeckers feed their young by regurgitation, inserting their bill quite far into the throats of their young as they deliver food to them. A visit can consist of one to three regurgitations per nestling. (Photo: adult male Pileated Woodpecker feeding male nestling)
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Pileated Woodpeckers Raising Young
Once their eggs (usually 3-5) hatch, Pileated Woodpeckers, like all parents, are kept busy providing their young with food. The nestlings are fed about every hour when small, but this stretches to every two hours after the nestlings are about a week old.
At first the adults enter the cavity to feed their young and only the tips of the parents’ tails are visible. Eventually the young manage to reach the cavity opening and can be seen at the entrance to the nest hole, waiting for food to be delivered. As they age, the nestlings find their voice when hungry and the woods reverberate with their distinctive and very adult-like call (https://www.allaboutbirds.org/guide/Pileated_Woodpecker/sounds). (Photo: female adult Pileated Woodpecker and male nestling)
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Changing of the Guard: Pileated Woodpecker Parents Share Parenting Duties
Recently I had the opportunity to observe nesting Pileated Woodpeckers, and I thought I would devote this week’s Naturally Curious posts to different aspects of my observations. I would like to thank Amber Jones and Dave Bliven for generously sharing their Picidae residents with me.
From start to finish, both Pileated Woodpecker parents are involved in raising their young and all that it entails. Together they excavate a nest cavity, usually in a dead or dying tree. Both have brood patches (areas on their undersides that lack feathers and are well supplied with blood vessels, allowing efficient transfer of body heat to eggs), and both incubate the eggs during the day (the male has night duty). The parents take turns brooding the nestlings and providing them with food. And finally, once fledging take place, both parents provide and help their young find food for several months. (Photo: male Pileated Woodpecker in nest cavity; female Pileated Woodpecker on nesting tree)
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