Blister beetles derive their name from the fact that they secrete a yellow blood-like substance called hemolymph which contains the blistering compound cantharidin. Severe burns and even poisoning can occur if the quantity encountered is large enough. (Baled hay containing the carcasses of blister beetles can be lethal to livestock that eat it.)
Defense isn’t cantharidin’s only function, however. Cantharidin is secreted by the male blister beetle and given to the female as a copulatory gift during mating. Afterwards, the female beetle covers her eggs with it as a defense against predators.
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The Common Green Darner (Anax junius) is one of our most common dragonflies. often seen near ponds. The family of dragonflies known as “darners” consists of species with large eyes and long abdomens that tend to rest infrequently and when they do rest, usually hang vertically. The Common Green Darner is the only North American darner in which the male and female usually fly in tandem when the female is laying her eggs on emergent vegetation.
Up to 50 of the world’s 5,200 dragonfly species migrate and the Common Green Darner is one of them. In the fall most (but not all) adult Common Green Darners migrate south to Florida, eastern Mexico and the West Indies. Huge clouds of migrating dragonflies have been seen along the East Coast, Gulf Coast and the Great lakes in autumn. Transmitters weighing 1/100th of an ounce that have been attached to migrating dragonflies confirm that they migrate much like birds. Just like avian migrators, they build up their fat reserves prior to migrating; they follow the same flyway as birds, along the Atlantic Coast; and like birds, dragonflies don’t fly every day but stop and rest every three days or so.
Some dragonflies mate and lay eggs along the way, while others do so when they reach their destination. The eggs hatch, larvae develop and the adults head north in the spring. Unlike birds, migration is only one-way for dragonflies. It is the offspring of the fall migrating generation that migrate north in the spring. Here in the Northeast, most arrive before any resident Common Green Darners have emerged. (photo: female Common Green Darner)
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How do you distinguish a millipede from a centipede – both multi-segmented arthropods that have a lot of legs? Although there are many less obvious differences, centipede bodies are relatively flexible and they have one pair of legs per body segment. Most of a millipede’s segments have two legs, and their tubular body is quite rigid.
Depending on the species, millipedes have between 80 and 750 legs, with most having fewer than 100, but they didn’t start out their lives with this way. When they hatch, millipedes only have three pairs of legs; every time they molt, they add more body segments and legs. When threatened, millipedes quickly coil their body into a spiral, protecting their legs and fragile underbody with their armor-like body plates (tergites).
If you come across a millipede, know that you’re looking at one of the earliest animals to breathe air and make the move from water to land. Pneumodesmus newmani, a fossil found in Scotland, dates back 428 million years and is the oldest fossil specimen with spiracles for breathing air.
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Everyone knows that grasshoppers disappear once cold weather arrives. Where do they go and what is their strategy for surviving the winter? Most grasshoppers overwinter as eggs. They mate, lay eggs and die in the fall. The female Red-legged Grasshopper, New England’s most abundant species of grasshopper, deposits clusters of eggs one to two inches deep in the soil in the late summer and early fall. During this process, a glue-like secretion cements soil particles around the egg mass, forming a protective “pod.” Each pod is roughly three-quarters to one-inch long and curved. The top third is dried froth, the bottom two-thirds contain 20 to 26 eggs. Each egg is just over 1/10th of an inch long and pale yellow.
In the spring, nymphs hatch out of the eggs, crawl up to the surface of the soil and start to feed on grasses and other herbaceous plants. It takes about three months for them to mature and begin the cycle all over again. (Photo: gravid female Red-legged Grasshopper in late summer)
There is a group of butterflies known as greater fritillaries, or silverspots (their underwings often have multiple silver spots). Three species of greater fritillaries can be found in the Northeast: Great Spangled, Atlantis and Aphrodite. All three are similar in appearance, with differences so subtle that the butterfly in a Naturally Curious post last month was mis-identified as a Great Spangled Fritillary, when it was actually an Atlantis Fritillary. Thanks to a sharp-eyed reader, Sue Elliott, this was brought to my attention. If you can approach a fritillary close enough to see the color of its eye, identification is a snap! Great Spangled Fritillaries have amber-colored eyes, Atlantis Fritillaries have blue-gray eyes, and Aprhrodite Fritillaries have yellow-green eyes. Can you identify the two species of fritillaries that are pictured? (Upper right, on thistle – Great Spangled Fritillary; main photo, on Joe-Pye Weed – Atlantis Fritillary)
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American crows obtain most of their food on the ground as they walk along in search of seeds, insects, frogs, snakes, bird nests and small mammals. Their hunting techniques are varied and most involve the use of their bill. In search of invertebrates, crows will probe the soil with their bill, flick aside leaves, dig in the soil and even lift cow paddies. They fish for tadpoles and dig nearly an inch deep with their bill for clams. In winter, their foraging continues and as these tracks indicate, when the snow is only a few inches deep they will walk around and around in a given area, probing tufts of grass for hibernating insects, mice, voles, or any other form of life these opportunists find.
Ambush Bugs are true bugs, in the order Hemiptera. (Although insects are often referred to as “bugs,” technically, only insects in this order are considered and referred to as bugs by entomologists.) All true bugs have piercing and sucking mouthparts, and wings which are membranous and clear at the tips, but hardened at the base.
Ambush Bugs are usually brightly colored (yellow, red or orange) and have thickened front legs which are used to capture prey up to ten times their own size. They live up to their name, patiently lying in wait, motionless, often in goldenrod flowers where they are very well camouflaged, for unsuspecting prey. The Ambush Bug, upon sighting prey, suddenly seizes the prey in its powerful forelegs and quickly dispatches it with a stab from its sharp beak. It then injects digestive enzymes into its prey, after which it drinks the resulting liquid innards.
This time of year you often see the smaller males riding around on the backs of the larger females while the females continue to feed. This behavior is part of the courtship ritual – males actively guard their mate prior to and following copulation. Mating takes place side by side, after which the female deposits her eggs among the leaves or on the stems of flowering plants. Look for Ambush Bugs in yellow and white flowers, especially goldenrod.
In the spring, the 4mm-long cynipid gall wasp, Diplolepis rosae, lays up to 60 eggs (through parthenogenesis) inside the leaf bud of a rose bush. A week later, the eggs hatch and the larvae begin feeding on the leaf bud. This stimulates the abnormal growth of plant tissue, and a Mossy Rose Gall, covered with a dense mass of sticky branched filaments, is formed. The gall provides the larvae with food and shelter through the summer. In late October, when the Mossy Rose Gall is at its most colorful, the larvae stop eating and pass into the prepupal stage, in which they overwinter inside the gall. In February or March, the prepupae undergo a final molt and become pupae. If the pupae aren’t extracted and eaten by a bird during the winter or parasitized by another insect, adult wasps exit the gall in the spring and begin the cycle all over again.
While meadows and fields are experiencing a sharp decline in insect life at this time of year, one habitat where insects remain active in the fall and often through the winter is ponds. Among the year-round active pond invertebrates are Predaceous Diving Beetles, which can still be observed as they row through the water, intermittently surfacing to thrust their abdomen above the water line in order to procure a bubble of air from which they breathe. Their middle and hind legs are fringed with long hairs, making them efficient at rowing through the water in search of prey or detritus to eat.
Predaceous Diving Beetles lay their eggs on and in plants above the waterline in early spring. When the eggs hatch, the larvae drop into the water. Mature larvae crawl out of the water to pupate in damp chambers on the shoreline. They emerge as adults and re-enter the water, where they remain active through the winter, under the ice. (Water Scavenger Beetles look a lot like Predaceous Diving Beetles, but they stroke first with one leg, then another, not simultaneously like Predaceous Diving Beetles, and they come to the surface of water head first to secure air.)
Black vine weevil larvae overwinter in the soil. In the spring, the flightless adults emerge and feed at night on the outer edges of leaves, causing the leaves to have a notched margin. They mate and lay as many as 500 eggs in the soil near the base of host plants. The larvae hatch in a week or two and feed on plant roots until cold temperatures drive them further underground. The larval stage is quite destructive, especially to landscape plants such as rhododendron and azalea. Female black vine weevils have the ability to reproduce parthenogenetically. Fertilization of eggs is required to produce males, but no males have been observed in North America. (photo: adult black vine weevil on Jack-in-the-Pulpit fruit)
A number of unrelated spider families in North America spin webs with funnel-shaped retreats. These spiders are all referred to as funnel weavers. The spider lies in wait in the funnel, and when an insect flies into or lands on the web, the spider rushes out, checks to see if it is prey, and if it is, bites it. Its venom is fast-acting, and as soon as the prey is largely immobile, the spider drags it back into its funnel to safely consume it out of sight. Many species’ funnel webs are horizontal, and found in grass and bushes, but others are vertical. Like most spiders, funnel weavers are nocturnal. Many species die in the fall, but a few live a year or two. If you find a funnel web inhabited, it is likely to be a female. Males spend most of their life wandering in search of a mate, and after finding one and mating a few times, often die.
Funnel weaving spiders are docile and non-aggressive, and their bite is rarely as bad as a bee sting. Funnel weaving spiders are sometimes referred to as “funnel web spiders.” True funnel web spiders are not found in North America, but in Australia, where their bite is considered harmful.
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.)
Milkweed leaves make excellent platforms for all kinds of insects, particularly those such as dragonflies and robber flies, which sit, wait and watch, surveying the landscape for prey to ambush. This robber fly could quite easily be mistaken for a bumblebee. However, the short, straight antennae and the presence of only two wings (instead of four) tell you it’s in the order Diptera (true flies). The pointed, stout proboscis, bearded face, fleshy feet and long, tapering abdomen narrow it down to a species of robber fly. Robber flies in the genus Laphria resemble bumblebees – they are typically quite hairy, with black bodies and yellow stripes on their abdomens. Like other species of robber flies, they hunt by perching and snagging prey such as other robber flies, bees, wasps or beetles. They often return to their perch, inject the prey with enzymes that dissolve its innards, and then have a long drink. Why mimic a bumblebee? To deceive unsuspecting honeybees, wasps and other insects that would make a good meal.
The Clymene Moth, Haploa clymene, is noted for the striking upside-down cross pattern on its forewings. Because of this design, some people refer to it as the “Crusader Moth.” A member of the Tiger Moth family (as is the Woolly Bear/Isabella Tiger Moth), the Clymene Moth can be seen flying day or night. Typically they inhabit deciduous forests and fields adjacent to them where the black, bristly larvae feed on a wide variety of plants, including willows, oaks, and members of the Aster family. In contrast to its white forewings, the Clymene Moth’s hind pair of wings is bright yellow. Its long proboscis allows it to reach deep inside the nectar-bearing hoods of Common Milkweed.
Beetles in the family Scarabaeidae share several characteristics, including specialized antennae. The last three to seven segments of each antenna form flat plates, or lamellae, that can be expanded like a fan (see Japanese Beetle insert) or folded together into a club (see June Beetle photo). When these plates are separated they are being used as sensory devices to detect odors. When folded together, the antennae are used as clubs by some species of fighting male scarabs. The next time you see a June Beetle, Rose Chafer or Japanese Beetle, take a second to inspect its antennae before parting company.
Swallowtails are North America’s largest butterflies, and their tropical relatives are the largest butterflies in the world. At this time of year, Tiger Swallowtails emerge from their chrysalises and seek nectar wherever they can find it, often in gardens. The two common species in the Northeast are the Eastern Tiger Swallowtail and the Canadian Tiger Swallowtail. Those of us living in northern New England are most apt to see the Canadian Tiger Swallowtail, which replaces the Easter Tiger Swallowtail this far north. Both species can be found further south. There are ways to tell these two swallowtails apart (although sometimes where their ranges meet, it can be difficult). The Canadian Tiger Swallowtail is smaller than the Eastern Tiger Swallowtail, but unless you have them side-by-side, this isn’t all that helpful. The easiest way to tell the two species apart is to look on the underside of the butterfly’s forewing and see if the yellow band along the margin is solid (Canadian Tiger Swallowtail, Papilio canadensis), or if it is broken up into spots (Eastern Tiger Swallowtail, Papilio glaucus). (Photo is of a Canadian Tiger Swallowtail)
This is the time of year when moths rule the nights. Many moths in the silkmoth family, Saturniidae, emerge in June, including giant silkmoths such as Luna Moths and Cecropia Moths. A smaller member of this family also appears at this time of year. While the 1 to 2-inch Rosy Maple Moth (Dryocampa rubicunda) wingspan doesn’t come close to many of the giant silkmoths’ 5 to 6-inch wingspan, its pink and white or yellow coloring is stunning. Adults emerge mid-May through mid-July in the late afternoon, and they mate in the late evening. Females begin laying eggs at dusk the next day in groups of 10-30 on leaves of the host plants (Red, Sugar and Silver Maples, as well as Box-elder and some oak trees). The eggs hatch in about 2 weeks and the larvae are referred to as Green-striped Mapleworms. They occasionally do considerable damage to their host trees when their population soars. In New England there is only one brood per summer, with the larvae pupating and overwintering underground.
To appreciate the parental demands on birds, consider the feeding habits of a pair of American Robins with a nest full of young. Both parents feed their 3 – 4 nestlings, delivering 6 – 7 feedings an hour, each one to a single nestling. (Parents tend to arrive with food at a particular location on the nest rim, so there is much jockeying for a position near this spot on the part of the nestlings.) Each nestling gets 35-40 feedings per day. This amounts to almost half a pound of food delivered to the nest every day for the 13 days that young are in the nest. Even then, the parents’ work is not done, as they continue to feed their fledglings for up to three weeks after the young leave the nest.
Slugs mate and lay eggs in the spring and fall, and can live 12 to 15 months. Eggs laid in the fall overwinter in this stage, and hatch in the spring. Some members of this generation of slugs may die in the fall, while others hibernate underground or beneath loose bark. The survival rate of the hibernators depends upon the harshness of the winter. Look in and under rotting logs to find slug eggs, and behind the bark of dying trees to find slug hibernacula.