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Insect Signs

Bagworm Moth Bags


If you find a tiny (1/2″ long) bundle of stick-like pieces of vegetation clumped together into a “bag” that is attached to a structure, you have discovered the abandoned home of a bagworm moth larva, and the overwintering site of bagworm moth eggs. The bags consist of parts of the vegetation that the larva was eating and then bound together with silk.

In the spring, the eggs hatch and the larvae all leave and build protective cases, or bags, for themselves, inside of which they live while feeding, growing and molting throughout the summer. As the larvae increase in size, they increase the size of their bags. Eventually the larvae attach the bags to branches, trees, etc. and pupate within them. Female bagworm moths are wingless, and thus are confined to life within a bag for their entire lives. Upon emerging, adult male bagworm moths seek out the females and mate with them before perishing. After laying eggs inside their bags, females exit and die.

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Milkweed Tussock Moths

9-6-16  milkweed tussock moth larvae 20160830_1764Milkweed Tussock Moth caterpillars are responsible for eating all portions of milkweed leaves but the largest veins that contain sticky latex. They can tolerate the cardiac glycosides within the milkweed plant that are toxic to most other insects as well as certain mammals and birds. Like Monarchs, these caterpillars retain the toxic compounds as adults, and are therefore avoided by many predators.

Female Milkweed Tussock Moths lay their eggs in masses on the underside of milkweed and dogbane leaves, which their larvae will eat. The hatching caterpillars are gray and hairy, but in no time they have developed the tufts of hairs that give them their name. When fairly young, the larvae tend to stay together, skeletonizing the leaves they consume. As they mature, the caterpillars tend to wander, and it’s unusual to find large groups of them on a single leaf.

Many of the insects that feed on milkweed have orange and black patterns as both larvae and adults. These colors serve as a warning to would-be predators. One of the adult Milkweed Tussock Moth’s main predators is bats. While the moth possesses these colors during its larval stage, as a pale brown adult (the stage that nocturnal bats prey on them) it lacks the bright coloration (which would provide little protection in the dark) but has an organ that emits an ultrasonic signal easily detected by bats. The signal warns that an attack will be rewarded with a toxic and distasteful meal, thereby deterring predation.

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Queen Ants Mating & Removing Wings

ant removing wings2  095Ants are social insects and live in colonies consisting of one or more queens, female workers and males. In most species the non-sexually mature female ants are wingless; only the males and the queen(s) possess wings. Periodically, often 3-5 days after a heavy rain, the winged ants emerge from the colony in large swarms in order to mate and create more colonies. Swarming behavior is usually synchronized with other nearby colonies, so large numbers (hundreds or thousands) of winged ants suddenly appear. After mating, the males die and the queens shed their wings and use the remaining wing muscles as a source of nutrients during the early stages of colony development. The shedding of wings is not a passive activity. The pictured ant is in the process of removing her fourth and final wing. She held each wing down with one leg while pulling it out with another. She then crawled off, leaving a pile of wings behind.

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Goldenrod Bunch Gall

goldenrod bunch gall 144Galls are abnormal plant growths that are caused by a number of agents, including insects. Each gall-making insect has a specific host plant and location (leaf, stem, bud) on which it lays its eggs in the spring, during the growing season. The egg-laying and/or hatching and chewing of the larva causes the plant to react by forming a growth around the insect. Galls of different species of insects vary in their shape and the gall maker can often be identified as a result of this.

Goldenrods are host to about 50 species of gall-making insects, two-thirds of which are midges, or tiny flies. Goldenrod Bunch Galls, also called Rosette Galls, are the result of an egg being laid in the topmost leaf bud of Canada Goldenrod, Solidago canadensis by a midge in the genus Rhopalomyia, often Rhopalomyia solidaginis. The stem of the goldenrod stops growing, but the leaves don’t. The resulting rosette of leaves provides shelter and food for the midge larva, as well as a host of other insects, including other midges. Adult Goldenrod Bunch Gall midges emerge from the galls in the fall, and females lay eggs in the soil. The larvae hatch within one to two weeks and spend the winter underground, emerging in the spring to start the cycle all over again. Interestingly, Rhopalomyia solidaginis lays all male or all female eggs, one or the other.

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Antlions Trapping Insects

8-14-14  antlions - 230The larvae of a predaceous group of winged insects (family Myrmeleontidae) that closely resemble dragonflies and damselflies are referred to as “antlions” – they have the ferociousness of a lion and prey mainly on ants. The manner in which an antlion traps its prey is ingenious. It excavates a conical pit in sandy soil (an antlion is also called a “doodlebug” because of the squiggly trails it leaves in the sand looking for just the right spot for a pit). Using its head as a shovel, it tosses out sand as it turns in a circle, digging deeper and deeper, until it forms a pit roughly two inches deep and three inches wide. The antlion lies at the bottom of the pit, covered by a thin layer of sand except for it pincer-like mandibles, which are ready to snatch prey at a second’s notice.

The slope of the sides of the pit is at the angle of repose – as steep as it can be without giving way – so when an ant accidentally steps over the edge of the pit and falls in, the sand beneath it collapses, carrying the ant to the bottom of the pit and into the pincers of the waiting antlion. If the ant tries to scramble up and out of the pit, the antlion tosses a load of sand at the ant, knocking it back down. The antlion then injects venom and digestive fluids into the prey via grooves in its mandibles, and drinks the innards of the ant through these same grooves.

The antlion’s anatomy is as unusual as its method of capturing prey. It has a mouth cavity, but no mouth opening, and no external opening for solid waste. Because digestion takes place outside of its body, the antlion doesn’t accumulate a lot of waste, but what it does accumulate stays inside of it until the antlion matures into an adult. This can be anywhere from one to three years, depending on the species. When fully developed, the antlion constructs a small, round pupal case out of silk and sand, in which it overwinters. It emerges from this case the following spring as a winged adult. (Thanks to Joan Waltermire and John Douglas for photo op.)

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Twelve-spotted Tiger Beetle Larva at Work

7-24-14 tiger beetle adult and larva 040Without doubt, I have one of the most erudite readerships in the land of blogs. Several people recognized this uncommon phenomenon. To clear up a few misconceptions, however, being a male, this dragonfly was not laying eggs. Neither was it fertilizing them – male dragonflies perform this act when coupled with a female. This Chalk-fronted Corporal had the misfortune to sun itself on a tiger beetle-inhabited patch of sand. One of the most aggressive groups of insect predators is the tiger beetle family. They are especially known for their speed – up to 5.6 mph, which is comparable to a human running 480 mph. If you watch an adult tiger beetle hunting, you’ll notice that it stops and starts frequently. This is because it runs so fast it goes blind — its brain has trouble processing the information it sees, and the beetle must stop to regain its sight.

The larvae of the Twelve-spotted Tiger Beetle live in tunnels that they dig in the sand (some of you noticed tiny holes near the dragonfly) that can be up to a foot deep. The larvae have hooks located on the back of their abdomen to anchor them to the side of the burrow. Tiger beetle larvae are also predators, and after digging a tunnel the Twelve-spotted Tiger Beetle will crawl up it until just the top of its head is visible. From this position the larva watches for prey wandering by. When it sees a potential meal, such as yesterday’s dragonfly, it flips backwards faster than you can blink an eye and grabs its prey, pulling it down as far as it can into its tunnel, where it safely feasts on its catch. The portion of the Chalk-fronted Corporal’s abdomen that was inside the tiger beetle tunnel was completely consumed except for the outer skeleton.

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Dragonfly Mystery Photo

7-23-14  dragonfly mystery photo 020Do you know what is happening in this photograph? All guesses welcome. The answer will be revealed tomorrow!. (Photo: male Chalk-fronted Corporal dragonfly, Libellula julia)

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Eastern Tent Caterpillars Hatching & Building Tents

eastern tent cat. FINAL 090The adult Eastern Tent Caterpillar moth lays her eggs in late spring or early summer on a tree whose leaves its larvae will eat (black cherry and apple trees are favorites). Two to three hundred eggs are deposited in a mass that encircles a thin branch. Within three weeks fully formed caterpillars develop inside the eggs. The caterpillars remain there until the following spring, when they chew their way out of the eggs just as the buds of the host tree are starting to open. As soon as the caterpillars emerge, they construct a silk tent within which they reside, enlarging it as they grow in size.

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Praying Mantis Egg Case

12-9-13 praying mantis egg case 057In the fall, after mating, the female praying mantis lays up to 400 eggs in a frothy liquid produced by glands in her abdomen. This one to two-inch long mass is attached to vegetation, often grasses and goldenrod stalks, about a foot or two off the ground. The frothy structure hardens, providing a protective case for the eggs. In the spring, miniature (wingless) mantises, called nymphs, will hatch from this egg case. When hatching, the nymphs appear all at once, crawling from between tiny flaps in the case and then hanging from silk threads about two inches below the case. Within an hour or two, after drying out, they disappear into nearby vegetation.

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Cecropia Moths Pupating

11-11-13 cecropia cocoon dissected  056Our largest North American native moth, the Cecropia Moth, Hyalophora cecropia, spends the winter as a pupa inside a cleverly-crafted 3” – 4”-long shelter, or cocoon, which it creates and attaches lengthwise to a branch while still in its larval stage. The Cecropia caterpillar, with the silk glands located near its mouthparts, spins not one, but two silk cases, one inside the other. In between the two cases, it spins many loose strands of very soft silk, presumably to enhance the insulating properties of the cocoon. Inside the inner case, the caterpillar splits its skin and transforms into a pupa. Come spring, an adult moth will emerge from the pupal case and exit the cocoon through one end which was intentionally spun more loosely, allowing the moth to crawl out the somewhat flexible tip. (Note: dissected cocoon was not viable.)

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Jewelweed Gall Midges

10-4-13 jewelweed gall  277Abnormal 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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Apple Scat

10-4-13 woolly bear scat 028At this time of year it’s not unusual to find the scat of various mammals consisting mostly of apple. Red Foxes, White-tailed Deer, Cottontail Rabbits, Porcupines and Black Bears, in particular, are all avid consumers of this appetizing fruit. Birds, including Purple Finches, Cedar Waxwings and Northern Mockingbirds, also include apples in their diets . While many insects drink the juice of apples, it’s not that often you see an insect like this Woolly Bear caterpillar (the larval stage of the Isabella Tiger Moth) consuming a sizable chunk of a McIntosh apple and leaving behind tell-tale scat. (Discovery by Sadie Richards)

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The Give and Take of Food in a Paper Wasp Nest

8-7-13  paper wasp nest 011Like 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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Goldenrod Ball Gall Fly Larva

3-22-13 goldenrod ball gall fly larva IMG_6182The round “ball” that is often present on the stem of goldenrod plants contains the overwintering larva of a fly (Eurosta solidaginis). A year ago an adult female fly laid an egg in the stem of the goldenrod plant. The egg hatched and the larva proceeded to eat the interior of the stem. As it did so, the larva excreted chemicals which caused the plant to grow abnormally, creating a ball-shaped “gall.” If you were to open a goldenrod ball gall today, you would probably find an overwintering larva (if a downy woodpecker or parasitic wasp hadn’t gotten there before you). Within the next few weeks the larva will pupate, and as early as April the adult fly will emerge from the gall, having crawled out the passageway that it chewed last fall. An inflatable “balloon” on its forehead allows the fly to burst through the remaining outermost layer of tissue at the end of the passageway. The adult fly lives about two weeks, just long enough to mate and begin the process all over again.

Hibernating Queen Wasps

2-7-13 hibernating wasp queen2 IMG_2680The 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.

Blueberry Stem Gall

12-20-12  blueberry stem gall IMG_7405If you happen to notice a ¾” to 1 ¼”- long, brown kidney-bean-shaped or round structure on a blueberry bush this time of year, you’ve come upon the blueberry stem gall – a summer and winter home for a dozen or so wasp larvae that will pupate and emerge in the spring as very small (less than 1/8”) black wasps (Hemadas nubilipennis). Last summer a female wasp laid her eggs in a tender, developing blueberry shoot. She then climbed to the tip of the shoot and stabbed it repeatedly, causing considerable damage. Within two weeks the eggs hatched, and the larvae began feeding, which, along with the egg-laying, stimulated the formation of the gall. Initially a blueberry stem gall is green and spongy; by fall it turns red, and by late autumn, it is brown and woody. Next summer, look for multiple holes in these galls that were chewed by the exiting wasps.

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!

Cecropia Moth Cocoon

This past summer there seemed to be more giant silkmoths than usual, including Cecropia Moths (Hylaphora cecropia).  (see ). Assuming many of these moths bred and laid eggs, and that most of the larvae survived, there are probably a large number of Cecropia cocoons in our woods.  Even so, it is not an easy task to find them, as they are so well camouflaged, and are often mistaken for a dead leaf.  Cecropia caterpillars spin silk and fashion it into a three-inch long, tan cocoon (giant silkmoths make the largest cocoons in North America) which they attach lengthwise to a branch or stem.  There is a tough but thin layer of silk on the outside, which protects an inner, thicker and softer layer of silk on the inside.  The caterpillar enters the cocoon through loose valves it makes in both layers, which are located at the tip of the cocoon’s pointed end.  Shortly after the larva crawls inside both of these layers, it pupates.  Its skin splits, revealing a dark brown pupa. For the rest of the winter and most of the spring, it remains a pupa.  In early summer it metamorphoses into an adult moth and exits the cocoon through the same valves  through which it entered.


Sawfly Cocoon

Sawflies are often mistaken for wasps, but there are subtle differences in appearance, including the thick “waist” of a sawfly compared to the threadlike waist of a wasp.  Their common name comes from the females’ sawlike ovipositor which they use to cut into plants and lay their eggs.  Certain species of sawflies overwinter as pupae inside cocoons that they attach lengthwise to twigs.  These cocoons are fairly small (the pictured cocoon is just over ¼” long).  Sawfly cocoons persist even after the adults emerge in the spring, as they are made of very tough material.   Look for capped cocoons during late fall and winter, and empty cocoons, sometimes with the cap still attached, the rest of the year.

Goldenrod Spindle Gall

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There are three fairly well-known galls (abnormal plant growths caused by a variety of organisms) on goldenrod – the goldenrod ball gall (round swelling in stem caused by a gall fly), the goldenrod bunch gall (leaves at top of plant are bunched up into a mass caused by a gall midge) and the goldenrod spindle gall (elliptical stem swelling caused by a moth).  The amazing thing about insect galls is that not only do they provide shelter for the insect, but they are nutritious and serve as the insect’s food supply as well.    The spindle-shaped galls are home to the larval stage of the goldenrod gall moth (Gnorimoschema gallaesolidaginis).  In the late fall the adult female moth lays an egg on a low goldenrod leaf, where it overwinters. The larva, or caterpillar, hatches out the following spring and makes its way from the now dead leaf to a newly sprouted goldenrod, where it eats its way through a bud and into the stem.  The goldenrod plant reacts to this activity by forming an elliptical swelling, or gall, around the area where the larva took up residence. The larva feeds and develops all summer.  Prior to pupating, it chews a tunnel all the way through the gall (this is the only stage in which the moth has chewing mouthparts), and then spins a silk cover for it.  The larva then returns to the cavity in the middle of the gall and pupates.  In the fall the adult moth crawls down the tunnel,  bursts through the thin layer of silk and then mates and lays eggs.

Signs of Striped Skunks

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If you are finding small, conical pits in your lawn, you probably have a striped skunk to thank for reducing your grub population.  During the spring and summer, invertebrates make up a large percentage of this nocturnal omnivore’s diet.  With the help of their well-developed sense of smell and their long nails (which make them excellent diggers), they locate, gain access to and consume subterranean insect larvae with relative ease.   Another sign of skunk activity, in addition to lawn divots, are the excavated ground nests of yellowjackets.  If they’ve met with success, skunks will often leave sections of empty, paper cells scattered about the nest site.  Apparently, even though yellowjackets can sting multiple times, they’re not very effective at discouraging foraging skunks.  Should you be so inclined, a close examination of skunk scat will reveal bits of insect exoskeletons, as well as the bones and hair of small rodents.  The pictured scat (next to the divot) contained, in addition to insect parts, the fur of another nocturnal animal, a flying squirrel.  (Thanks to Emily and Joe Silver for photo op.)

Pine Cone Willow Gall

Galls are abnormal plant growths that can be caused by insects, fungi, bacteria, nematode worms and mites.  Insects cause the greatest number of galls and induce the greatest variety of structures.  Galls provide both food and shelter for the organisms living within them.  Galls develop during the growing season, often in buds and on leaves.  Pine Cone Willow Galls, named for their resemblance to small pine cones, are found on willows, typically in terminal buds.  A gall midge (Rhabdophaga strobiloides) is responsible for the willow bud going haywire and developing  abnormally. (No-one has determined exactly how insects cause galls, whether it’s the act of laying eggs in or on the plant, or if it’s somehow connected to the chewing of the larvae into the plant.)    Each gall-making insect has a specific host plant, or small group of related plant.  The galls that each insect species induces and lives in while developing into an adult has a recognizable shape and size.  When you think you’re seeing pines cones on willow trees, you’re not hallucinating, you’ve just discovered the temporary home and food supply of a tiny fly, known as a midge.

American Lady Larva

The American Lady larva is very distinctive with its branched spines and white bands across its abdomen.  One of its favorite foods is Pussytoes, a member of the Aster family.  The larva feeds inside a shelter it makes by tying up several leaves with silk.  In the photograph, the larva has incorporated the flower heads of Pussytoes into its shelter.  Not only is the larva feeding and growing inside this 1 ½ ”-long  cavity, it also shed its skin.  To see an adult American Lady butterfly, go to .  Soon after the larva forms a chrysalis and pupates, a butterfly emerges and starts its migration south for the winter.

Tobacco Hornworms & Brachonid Wasps

Tobacco Hornworms, Manduca sexta (often found feeding on tomato plants and confused with Tomato Hornworms, Manduca quinquemaculata) are often the target of a species of Brachonid wasp that parasitizes beetle, moth, fly and sawfly larvae. The adult wasp lays her eggs inside the hornworm with her long ovipositor. The eggs hatch and the wasp larvae feed on the caterpillar. Eventually the wasp larvae emerge and form white pupa cases on the skin of the dying hornworm larva, inside of which they transform into winged adults. Braconid wasps are extremely good at locating hornworms, even when there are very few to find. Because they parasitize hornworm, cabbage worm, aphid and gypsy moth larvae, Braconid wasps are considered important biological control agents. If you want to discourage Tobacco Hornworms in your tomato patch, allow the wasps to complete their metamorphosis – this accomplishes both the demise of the hornworm, as well as an increased population of Braconid wasps.