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Larvae

Eggs Of Migrating Generation Of Monarchs Hatching

7-19-12 monarch eating eggshell IMG_4494

The Monarch eggs that are hatching now contain the larvae that will metamorphose into the butterflies that will migrate this fall to central Mexico. Unlike earlier-hatching generations that only live six to eight weeks, the Monarchs that result from late summer and early fall hatchings live six to nine months. Part of the reason for this difference in life span is that, unlike the earlier generations that mate soon after emerging from their chrysalides, late-hatching Monarchs postpone mating (reproductive diapause) until the end of winter, thereby conserving energy for their two to three thousand-mile, two-month migration. (Photo: monarch larva’s first meal – its eggshell.)

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Case-bearing Leaf Beetles Eating & Growing

8-1-16 case-bearing leaf beetle 110It’s not every day that I discover a species I’ve never seen before, but when it comes to insects, it happens regularly.  Rarely, however, are they as interesting as the Case-bearing Leaf Beetle I observed on a blackberry leaf recently.  An oval, brown, stationary case about ¼” long was at a 45° angle to the leaf it appeared to be attached to it.  Upon closer inspection and with a bit of probing, a head and six legs appeared at the leaf end of the case, and the case began to move.

How its case was created is as, or more, interesting than the beetle itself.  The adult female Case-bearing Leaf Beetle lays an egg and wraps it with her fecal material as she turns the egg, until it is completely enclosed.  Once hardened, the feces create a protective case for both the egg and eventually the larva.  When the egg hatches, the larva opens one end of the case, extends its head and legs, flips the case over its back and crawls away.  As the larva eats and grows, it adds its own fecal material to the case in order to enlarge it.  Eventually the larva reseals the case, pupates and then emerges as an adult Case-bearing Leaf Beetle.  If it’s a female it then prepares to mate, lay eggs, and recycle its waste.

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Gypsy Moth Caterpillar Explosion

e-gypsy moth caterpillars 273The Gypsy Moth was introduced into the United States in 1869 by a French scientist living in Massachusetts. Since then its range has expanded to include the entire Northeast south to North Carolina and as far west as Minnesota and Iowa.  The consequence of the introduction of this insect is staggering.  According to the U.S. Dept. of Agriculture, since 1980, the Gypsy Moth has defoliated close to a million or more forested acres each year. In 1981, a record 12.9 million acres were defoliated. This is an area larger than Rhode Island, Massachusetts, and Connecticut combined.

The Gypsy Moth females lay their eggs, usually on host tree trunks, in late summer.  The eggs overwinter and hatch in the spring.  Gypsy Moth caterpillars feed on a variety of species of shrubs and trees, with White Oak being their preferred host, metamorphose, mate and repeat this process.   Usually their numbers are not overwhelming, but due to the weather conditions we’ve been experiencing, the caterpillar population has skyrocketed in some areas, especially in southern New England.

Conditions were very dry in parts of New England in May 2014 and May 2015, which impeded the growth of a certain kind of Japanese fungus (Entomophaga maimaiga) that keeps the Gypsy Moth caterpillar population under control. Without this fungus present to keep their numbers in check, Gypsy Moths have flourished.   Although there was some rain this spring, there were many areas that did not get enough to benefit the fungus, and in these areas, trees are now stripped of their leaves.  It is possible in places in southern New England to track the pattern of rainfall simply by looking at where trees are still in full leaf.  Fortunately, the time has come for Gypsy Moth caterpillars to pupate, so most of this year’s destruction has already occurred.  Here’s hoping for a rainy May next year.

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Rosy Maple Moths Emerging, Mating & Laying Eggs

6-13-16  rosy maple moth 059Rosy Maple Moths (Dryocampa rubicunda) are easy to recognize, with their pink and yellow woolly bodies, pink legs and pink antennae.  Many adults are emerging from their pupal cases now, having spent the winter underground as pupae. Once metamorphosis is complete, the adult moths lose no time in finding mates and laying eggs, not stopping to even eat.  These members of the family Saturniidae are most active during the first third of the night, reducing their body temperature and activity in the morning and afternoon.

Mating takes place at night on the underside of a leaf, and 24 hours later the female lays clusters of 10-30 eggs (a total of 150 – 200 eggs) on the underside of the leaves of the larvae’s host plants, most often maples and oaks.  When the eggs hatch, the larvae usually remain on the same tree throughout their larval stage.

Known as Green-striped Mapleworms, the larvae initially feed together, but become independent feeders as they age.  Mapleworms change color as they develop.  When young, most have black heads and yellow bodies, but with age their heads turns reddish-brown and their bodies assume a shade of green.

In New England there is only one brood per summer; further south, there are multiple broods.

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Spotted Salamander Larvae Soon To Emerge From Eggs

spotted salamander eggs2  040Roughly a month after spotted salamanders participate in frenzied courtship dances, deposit spermatophores (males) and take the spermatophores into their bodies (females), the resulting eggs have developed into larvae.  These juvenile, gilled salamanders are still contained inside the gelatinous eggs, but the eggs are dissolving fast, and the larvae will soon be swimming free within the vernal pools where the eggs were laid.

Many spotted salamander larvae do not survive this long.  Eastern newts, caddisfly larvae, leeches, fly larvae and even turtles feed on the nutritious eggs.  Meteorological conditions also contribute to the fate of spotted salamander eggs.  Their situation is especially precarious because they develop in vernal pools, which often dry up by summer’s end, thus forcing a rapid metamorphosis for amphibious inhabitants.  Hot temperatures can evaporate the water before metamorphosis is completed, and cool temperatures can slow down their development.  Inevitably some will survive to adulthood, and  the inch-and-a-half to two-inch salamanders (see insert photo), having shed their gills and developed lungs, will adapt to a terrestrial life.

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Goldenrod Ball Galls Provide Important Source of Winter Food for Downy Woodpeckers

12-11-15 goldenrod ball galls 058A number of insects cause goldenrod plants to form galls – abnormal growths that house and feed larval insects. The Goldenrod Ball Gall is caused by a fly, Eurosta solidaginis. The fly lays an egg on the stem of a Canada Goldenrod (Solidago canadensis) plant in early spring, the egg hatches and the larva burrows its way into the stem; the plant reacts by forming a gall around the larva. The larva overwinters inside the gall, pupates in late winter and emerges in early spring as an adult fly. Prior to pupating, the larva chews an exit tunnel to, but not through, the outermost layer of gall tissue. (As an adult fly it will not have chewing mouthparts so it is necessary to do this work while in the larval stage.)

Downy Woodpeckers (and Black-capped Chickadees) have discovered this abundant source of winter food, and dine on the larva after chiseling a hole into the gall. Downy Woodpeckers tend to make a tidy,narrow, conical hole by pecking, while Black-capped Chickadees tend to make a messy, large, irregular hole by grabbing bits of the gall with their bill and tugging them free. While woodpeckers prefer larger galls that are located high on goldenrod plants growing near wooded areas, these are not the only factors taken into consideration.

A woodpecker extracts the fly larva through the tunnel the larva excavates prior to pupating, as this facilitates rapid removal of the larva. Downy Woodpeckers can determine whether or not a gall has an exit tunnel, and if it doesn’t, they usually abandon the gall without drilling into it. The likelihood of smaller parasitic wasp larvae occupying the gall (and a plump fly larva not being present) is much greater if there is no exit tunnel, and these smaller prey apparently are not always worth the woodpecker’s time or energy.

NB: Correction: this week’s Mystery Photo was of a Gray Birch (Betula populifolia) bract, not a Paper, or White, Birch (Betula papyrifera) bract. While similar, there are differences between these two species of birch that I should have recognized (especially when looking at the leaf!). Thanks to Kathy, an alert blog reader, who caught this error.

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Snowberry Clearwing Larvae Pupating

snowberry clearwing larvae 125The Snowberry Clearwing (Hemaris diffinis), a type of Sphinx moth, is one of several daytime-flying “hummingbird moths,” so-called because of their ability to hover while drinking nectar from a flower, and because of the humming sound they make, much like a hummingbird. The yellow and black bands of the Snowberry Clearwing’s abdomen also cause it to be mistaken for a bumblebee. The most distinctive thing about this moth is that a large portion of its wings are transparent, due to scales falling off.

Snowberry Clearwings are often seen around the time that beebalm is in bloom, in July and August. The females entice the males with a pheromone that they produce from glands at the tip of their abdomen. After mating, the females lay their tiny, round, green eggs on their larval food plants. Like many Sphinx moths, the larvae have “horns” at the end of their bodies. Most Snowberry Clearwing larvae are green, but they can be brown, as well. Both colors enable them to be well camouflaged as they feed on the leaves of honeysuckle, viburnum, hawthorn, snowberry, cherry, mint, and plum. The caterpillars are active until late fall, when they drop to the ground, spin a loose cocoon and pupate, partially protected by leaf litter. The pupa spends the winter hidden under the leaves, and the adult moth emerges the following spring. (Thanks to Tom Wetmore and Heidi Marcotte for photo opportunity.)

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