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Larvae

Milkweed Tussock Moth Caterpillars Feeding

milkweed tussock moth2 038Female 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 and make them resemble little mops. When still fairly young, the siblings stay together, skeletonizing the leaves they consume, leaving only the strongest veins that contain sticky latex. As they mature, the caterpillars tend to wander, and it’s unusual to find large groups of them on a single leaf. At this point they often cut through a vein in order to prevent the latex from reaching the area of the leaf where they are feeding. (Older monarch caterpillars use this same tactic.) Like monarchs, milkweed tussock moths, because they’ve consumed the cardiac glycosides contained in milkweed and dogbane leaves, are toxic to predators.

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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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Second Brood of Woolly Bears Hatches

8-18-14  woolly bear 093Typically we start seeing Woolly Bear caterpillars in October, when they are searching for sheltered spots in which to spend the winter as larvae. With only two months between now and then, it came as a surprise when my great nephew and budding naturalist Eli Holland discovered a very young Woolly Bear recently. It turns out that in New England, there are two broods of Isabella Tiger Moths (whose larval stage is the Woolly Bear). The caterpillars that hibernated last winter emerged from hibernation this past spring, pupated, transformed into adult Isabella Tiger Moths, and proceeded to mate and lay eggs. It is these eggs that have recently hatched, and the Woolly Bear caterpillars that are no bigger than the length of your baby fingernail right now will be eating dandelions, grasses, nettle and meadowsweet nonstop for the next two months in order to survive the coming winter.

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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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Tortoise Beetle Larvae Making Fecal Shields

8-1-14  tortoise beetle larva with fecal shield 049Instead of discarding feces, or frass, some insects save their waste matter for defensive purposes such as “fecal shields.” These are coverings over the back of the larvae that are made largely of feces and provide either physical or chemical barriers to predation. Adult Tortoise Beetles have a type of shield (hence, their name), but it is formed from expanded, hardened forewings, and is not a fecal shield. The larvae of these beetles have fecal shields which serve as chemical deterrents, preventing most predators from even touching them. The deterrent in the feces comes from the beetles’ food source — plants in the order Solanales. Tortoise Beetle larvae have what is known as a “fecal fork” on their last abdominal segment, which they hold over their body. The larvae maneuvers its muscular, telescopic anus, or “anal turret” in such a manner as to excrete its feces and bits of shed exoskeleton onto the fecal fork, forming an umbrella-like fecal shield.

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Caterpillars Molting

6-25-14 caterpillar molting 044A caterpillar is the larval stage of a moth or butterfly. It is the only stage that has chewing mouthparts, and therefore a caterpillar spends most of its waking hours eating. This consumption of food results in massive growth, making its skin/exoskeleton very tight. When this happens, a hormone called ecdysone is produced, prompting the caterpillar to molt, losing its old exoskeleton (to left of caterpillar in photo) under which is a new and larger exoskeleton. After the molt, while the new exoskeleton is still soft, the caterpillar swallows a lot of air, which expands its body. Then, when the exoskeleton hardens, it lets the air out and has room for growth. Caterpillars molt four or five times as they grow. Each different caterpillar stage is called an instar. (Photo: Forest Tent Caterpillar)

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Fern Balls

fern ball 216At this time of year, many new sterile fern fronds have “fern balls” at their tips – something has taken the last few inches of the tip of the frond and stitched it together into a ball-shaped shelter bound with silk. If you open one of these balls, you may find frass – droppings from the immature insect that was dwelling within the ball while consuming the terminal leaflets of the fern. Sometimes, but not always, you’ll find the larva responsible for the frass. Many species of ferns, as well as other plants, are host to many species of larvae, and many of these larvae are immature moths. Pictured is Christmas Fern, Polystichum acrostichoides, which is likely the host of the larva of Herpetograma sphingealis, the Serpentine Webworm Moth, or its close relative, H. aeglealis. Larvae live in these shelters for about a month before pupating and emerging as small, brown moths.

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