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Larvae

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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Leaf Miners

9-29 leaf miners IMG_6836A leaf miner is the larval stage of an insect (primarily moths, sawflies and flies) that feeds on leaf plant tissue. Most of these insects feed for their entire larval period within the leaf, creating tunnels between the upper and lower leaf surfaces. Some will pupate within the leaf mine, while others cut their way out when they are full-grown and pupate in the soil.

The pattern of feeding tunnels, as well as the pattern of droppings, or frass, within them (darker sections of tunnels), combined with the species of plant on which they occur, can sometimes identify the species of insect that created the mines. A moth larva, the Common Aspen Leaf Miner (Phyllocnistis populiella), leaves delicate, serpentine mines (see photo) that are diagnostic of this species.

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Second Generation Calico Paint Moth Larvae Feeding & Resting

9-16-15 calico paint 111In the Northeast, Calico Paint Moths (Cucullia convexipennis), also called Brown-hooded Owlets, produce two generations a summer. The larvae of the first generation mature in July, and the second generation matures from late August into October. Calico Paint larvae are often found on aster and goldenrod plants, resting on stems (often head down) in plain sight during the day. First generation larvae feed on the leaves and the second generation consumes the flowers of these plants. The comparatively drab, brown adult moths they turn into can often be found on Wild Bergamot and Common Milkweed flowers in the early evening. (Thanks to Joan Waltermire for photo op.)

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Pandorus Sphinx Larvae About To Pupate

9-4-15 pandorus sphinx 033The family Sphingidae consists of sphinx (also called hawk) moths. In their larval stage, these moths are often referred to as hornworms, because of the horn, eyespot or hardened button they all possess at the far end of their bodies. (Many gardeners are familiar with the Tobacco Hornworm (Carolina Sphinx Moth), a voracious consumer of tomato plants.)

Before overwintering as pupae, hornworm larvae feed continuously. The pictured Pandorus Sphinx (Eumorpha pandorus) feeds on both grape and Virginia creeper foliage. This particular hornworm comes in four colors – green, orange, pink or cinnamon and can grow to a length of 3 ½ inches before pupating. Each of the white spots surrounds a spiracle, or tiny hole through which air enters the hornworm’s body. A horn is present up until the last instar, or stage, of the larva’s life, at which point it is replaced by a button (see insert) that resembles an eye. The larva will soon burrow into the soil, spend the winter as a pupa, and emerge as an adult moth in the spring.(Thanks to Sadie Richards Brown for finding and caretaking this caterpillar until I could photograph it.)

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Caddisflies Laying Eggs

9-3 caddisfly eggs & larvae 402Most caddisflies lay their eggs in or near ponds or streams. A very few species (in the family of northern case makers, Limnephilidae) deposit their eggs above the water on aquatic vegetation in a one- to-two-inch-long mass of jelly (some species’ eggs lack the jelly). Up to 800 eggs (the tan spots within the jelly in yesterday’s post) are laid at one time in one mass. Depending on the species, the eggs take from several weeks up to ten months to hatch. These masses are usually situated so that once the eggs hatch, the larvae will drop down into the water, where they will spend their larval and pupal stages.

Caddisflies are closely related to butterflies and moths, and one of the features they have in common is that the larvae have silk glands in their lower lip. Thanks to the ability to spin silk, the caddisfly larvae build portable cases or attached retreats out of natural material that is available. Some species build elongate tubes out of pieces of plants, sand, sticks or pebbles and reside in them while they drag them along with them wherever they go. Other species attach their cases with silk to crevices in or the bottom of stones in streams. Each species of caddisfly larva always constructs the same type of case, so that you can often tell the genus or even species of caddisfly by the appearance of its case.

The larval stage of a caddisfly can last two to three months or up to two years, depending on the species. Most species spend the winter as active larvae. When it is ready to pupate, the larva attaches its case with silk to something immoveable, such as a large rock. Inside its case, the larva spins a cocoon and eventually pupates inside of it. In two to three weeks the sharp-jawed pupa cuts its way out of its cocoon and floats up to the surface of the water where it emerges as a winged adult, often using its pupal skin as a raft for support during this process. Adult caddisflies live for about 30 days, during which time the males form mating swarms to attract females. After mating takes place, the egg-laying begins.

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Baltimore Checkerspot Larvae Feeding On Turtlehead

Baltimore checkerspot larvaeAt this time of year, just as Turtlehead is flowering, a butterfly known as the Baltimore Checkerspot is mating and laying bright red eggs on the underside of Turtlehead’s leaves. This is the only plant on which Baltimore Checkerspot eggs are laid, and the only plant which the larvae eat. When the eggs hatch, the tiny larvae proceed to spin a web that envelopes them and the leaves of the Turtlehead plant that they are eating. They eat profusely, enlarging the web as they expand the area to include uneaten leaves. Eventually, as fall approaches, they will spin a pre-hibernation web where they remain until late fall when they migrate down into the leaf litter. While most butterflies and moths overwinter as eggs or pupae, the Baltimore Checkerspot remains in its larval stage until spring, when it forms a chrysalis, pupates and emerges as an adult butterfly.

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