An online resource based on the award-winning nature guide – maryholland505@gmail.com

Insect Signs

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.


Common Aerial Yellowjackets

Common Aerial Yellowjackets derive their common name from the fact that their nests are often aerially constructed, unlike the underground yellowjackets we’re more familiar with. Being in the same genus, it’s not surprising that Bald-faced Hornets and Common Aerial Yellowjackets build nests that are almost identical. The nests of both species have two to six horizontally-arranged layers of comb (for eggs and larvae) inside several layers of protective paper envelopes. The easiest way to tell which species made a nest is to see if there are yellow (yellowjacket) or white ( hornet) markings on the residents. The yellowjackets on the outside of the nest in the photograph are all busy making paper-mache out of wood fiber and applying it to their nest in order to enlarge it.


Monarch Butterfly Chrysalis

Of the multitude of discoveries that every summer offers us, one of the most magical is that of  a Monarch Butterfly chrysalis.  While locating a Monarch larva is not all that difficult, especially when they are as prolific as they are this summer, finding a chrysalis doesn’t happen all that often. Most butterfly chrysalises are a rather drab brown, but the Monarch’s is a beautiful green which serves to camouflage it in fields where the caterpillars feed on milkweed and eventually pupate (form a chrysalis).  The Monarch caterpillar, when mature, usually seeks a sheltered spot under a leaf or branch where rain will not cause the silk button by which it hangs to disintegrate.  The chrysalis in the photograph is attached to a blade of grass which was anchored with silk to another blade of grass in order to make it more secure.  No matter how many I’ve seen, each one still takes my breath away.


Botfly Puparium

Congratulations on some very creative guesses!  Yesterday’s post  was a botfly puparium – a hard case made from an insect’s larval exoskeleton (skin) that covers and protects the pupa.  Most insects that go through complete metamorphosis (egg, larva, pupa, adult) don’t have this added protection for their pupal stage, but certain flies, including botflies, do.  Botflies are fairly large, hairy flies that resemble bumblebees and are internal parasites of many species of mammals, including humans. Depending on the species, the botfly deposits its eggs on or near the host animal, or on another insect, such as a mosquitoe or housefly, which carries them to their host. The eggs of some species of botflies are ingested or inhaled; those of other species hatch and the larvae bore into their host. After entering and crawling around inside of the host animal for a week or so, most species of botfly larvae settle in a spot just under the host’s skin and remain there for three to ten weeks, consuming the flesh of its host.  The lump, or “warble,” that forms just under the host’s skin where the botfly resides increases in size as the larva grows. A tiny hole chewed in the skin allows the larva to breathe, and eventually it exits through this hole.  The larva falls to the ground, where it pupates in the soil and later emerges as an adult botfly. (The two yellow bumps at one end of the puparium are spiracles, through which the pupa breathes.) The whole story of this particular puparium is that Jeannie Killam  found it in her old farmhouse’s kitchen cupboard, where it probably popped out of a visiting mouse.  (Illustration is of a human botfly.)


Monarch Butterfly Eggs Hatching

It appears that this may be a good year for monarchs in the Northeast, as with very little looking, you can find their eggs as well as young monarch caterpillars. Look on the underside of the top leaf or two on young milkweed plants – these leaves are tender and monarchs often lay their tiny, ribbed eggs there (usually one per plant) as they (leaves) are ideal food for young larvae. The first meal a monarch larva eats is its egg shell. It then moves on to nearby milkweed leaf hairs, and then the leaf itself. Often the first holes it chews are U-shaped, which are thought to help prevent sticky sap (which can glue a monarch caterpillar’s mandibles shut) from pouring into the section of leaf being eaten.


Close-up of Entire Organ Pipe Mud Dauber Nest

The images in a slideshow are smaller than if they were posted individually, so I thought I would include a single shot of the first image, showing all of the cells in the nest’s three tubes.


Inside Look at Organ Pipe Mud Dauber Wasp Cells

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Each “pipe” of the Organ Pipe Mud Dauber nest consists of several sealed cells (four, in this photograph), each stuffed with spiders (typically orb-spinning spider species) and one wasp egg. When the egg hatches, the white wasp larva consumes the paralyzed spiders, which are still fresh because they are still alive. Eventually, upon finishing the spiders, the larva will form a pupa case, and spend the winter inside it. In the spring the adult wasp will emerge from the case and chew its way out of the mud cell. If you look closely at the open, back side of these three “pipes” you can see that the oldest pipe is on the left, and contains cells with wasp larvae, whereas you can see mud dauber eggs lying on top of the spiders in two of the cells on the far right, in the most recently built pipe.


Organ Pipe Mud Dauber Wasps

There are basically two groups of wasps: 1) social wasps, such as hornets, yellowjackets and paper wasps and 2) solitary wasps, species that live solitary lives and typically hunt prey for their larvae (the adults consume nectar). Mud daubers are a type of solitary wasp.   Organ Pipe Mud Daubers builds cell out of mud in which they put prey (usually spiders) that they have stung and paralyzed, but not killed. They then lay an egg on top of the spiders, and seal the cell. After the egg hatches, the larval wasp consumes the still-fresh spiders, pupates, emerges as an adult wasp and chews its way out of the cell. In this picture a female Organ Pipe Mud Dauber wasp has collected a ball of mud and is applying it to the most recent cell she is making. The name “organ pipe” comes from the shape of the “pipes”, which consist of several cells, placed end-to-end, with the most recent cell at the bottom. (Notice the new, wet mud is darker in color.)


Leafcutter Bee Cell Leaf Sections

At the risk of boring readers, I wanted to include one final Leafcutter Bee post, showing the two basic shapes that these bees chew out of leaves in order to make their incubator/nursery cells.  There are oblong pieces, roughly an inch long, as well as perfectly round, ¼-inch diameter pieces.  Each cell consists of several layers of oblong pieces rolled lengthwise which are sealed at one end with a round piece of leaf.  The round end pieces appear to be glued into place (perhaps with the pollen/nectar mixture?) at one end of the cell, leaving the opposite end open.  The cells are arranged end-to-end, with the open end of the cell placed against the sealed end of the next cell.  Together they form a nest that is somewhat cigar-shaped and is typically located a few inches down in the soil, or in a cavity.


Inside View of Leafcutter Bee Cell – Larva and Pollen Supply


Leafcutter Bee Cell

Congratulations to those who recognized yesterday’s Mystery Photo!  The tiny green cells are made from the leaves of almost any deciduous trees, and are cut and folded by leafcutter bees (Megachile genus). These solitary bees are about the size of a honeybee, but are much darker, almost black. They construct cigar-like nests (often in soil, holes in wood made by other insects, or plant stems) that contain several cells. After gathering and storing a ball, or loaf, of pollen inside the cell, the bee lays an egg and seals the cell shut. When the egg hatches, the larval bee feeds on the pollen and eventually spins a cocoon and pupates within it. An adult bee emerges from the cocoon and usually overwinters inside the cell. In the spring the bee chews its way out of the cell. Leafcutter bees pollinate wildflowers, fruits and vegetables and are also used as pollinators by commercial growers of blueberries, onions, carrots and alfalfa. (Photo submitted by Jan Gendreau.)


Bloodroot Seeds and Myrmecochory

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Bloodroot seeds, as well as the seeds of as many as 5% of flowering plants, have a fatty white appendage called an elaiosome attached to them which ants are very fond of.  This adaptation benefits both the ants as well as the plant.  The ants collect the seeds and take them down into their tunnels where they feed the elaiosomes to their larvae. The actual seeds are discarded underground, often in with ant compost, where their chances of germinating are enhanced. The dispersal of seeds by ants is referred to as myrmecochory. As the photographs indicate, ants don’t always wait until the seeds have dropped out of the seed pod to collect them.


Rusty Tussock Moth Egg Case

There are many species of tussock moths, and in their larval, or caterpillar, stage, most are covered with tufts of hair-like setae, some impressively long.  The female rusty tussock moth, Orgyia antiqua, is flightless, so after emerging from her cocoon, she stays put, releasing alluring pheromones and awaiting the arrival of a male suitor.  After mating, she lays up to several hundred eggs on top of her empty cocoon and then dies.  The flat-topped, cylindrical eggs (with a dark depression on their top) overwinter, and as soon as leaf buds start opening, the eggs hatch, with ready-made meals inches away.  Larvae feed on the leaves of birches, oaks, crabapples and black cherry, among others.  Pictured is an egg mass on an apple leaf.

 


Honeybee Hives

Rarely do you see or hear about honeybees attempting to construct a hive outdoors that isn’t inside a hollow “bee tree” or in a rock crevice.  Occasionally they do attempt it, but as the empty cells in this exposed comb attest to, honeybees aren’t likely to make it through a Vermont winter without some shelter for their hive, even a winter as mild as the one we just experienced.


Blackberry Knot Gall

12-28-10      Blackberry Knot Gall

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Winter is a good time to look for galls (abnormal plant growths caused by different agents, including insects, fungi, mites and bacteria) such as the blackberry knot gall, which is much more noticeable when there are no leaves to hide it. Whereas many galls are inhabited by a solitary insect, the blackberry knot gall contains many individual chambers, each containing the larva of the tiny wasp Diastrophus nebulosus. During the spring and summer months, this little wasp deposits eggs into the ridged stems of blackberry which stimulates the plant’s tissue into abnormal growth along the stem. This particular colonial gall can be six inches in length, although two or three inches is more typical (the more eggs that are laid, the larger the gall).  The eggs hatch and the larvae overwinter inside the gall. Adult wasps emerge in the spring and chew their way out of the gall, leaving tiny holes along the gall’s lumpy ridges. In the first photograph you can see where a hungry predator has worked its way into two of the larval chambers.  In the second, multiple chambers and larvae are exposed (sacrificed for the sake of knowledge, but popular food for chickadees on a very cold morning).

 


Mud Dauber Wasp Nest

There are many species of mud dauber wasps in New England that use mud to make cells for their eggs, developing larvae and pupae.  One of them is Pison koreense, a small, black wasp with a wingspread of less than half an inch.  This particular wasp is native to Korea, China and Japan, and was accidentally introduced in the United States after World War II.  Like other mud daubers, this wasp constructs one cell at a time with her mandibles; there can be anywhere from 1 to 12 mud cells (each roughly ¼” long) in a nest, which is often located in a crevice or behind bark.  She then hunts for spiders, stinging and paralyzing them before carrying them back to the cell, into which she stuffs them.  After collecting 20 – 30 spiders, she lays a tiny white egg on the last (and often largest) spider to be placed in the cell.  She then flies off and collects mud with which she seals the cell.   The egg hatches, the wasp larva consumes the live spiders and then pupates, spending the winter inside a cocoon inside the mud cell.  In the spring the adult wasp emerges from the cocoon and chews her way out of the cell, leaving a circular exit hole.


Beech Bark Disease

 Anyone familiar with the beautiful, smooth, gray bark of American beech is well aware that the forest landscape is changing, in part due to the disease that is affecting American beeches. Beech bark disease is caused by not one, but two, agents – an insect and a fungus.  The bark of an American beech is initially attacked and altered by the soft-bodied scale insect, Cryptococcus fagisuga, after which it is invaded and killed by fungi, usually Nectria coccinea var. faginata or N. gallegina. This scale insect was accidentally introduced to Nova Scotia around 1890 and since then has spread far and wide, affecting large American beech trees (over 8 inches) the most.  Pale yellow eggs are laid by the yellow female scale insects (there are no males – they reproduce through parthenogenesis) on the bark of beech trees in mid-summer and hatch in the late summer or fall.  Larvae begin to feed on the bark until winter when they transform into a stage that has no legs and is covered with wool-like wax. The white wax secreted by beech scale insects is the first sign of the disease – heavy infestations of beech scale can cover tree trunks with white wax. Serious damage results only after the invasion of the bark by either one of the fungi mentioned, presumably through injuries made by scale feeding activity.

 


Staghorn Sumac Seed Heads and Their Inhabitants

If you pull apart a red, fuzzy seed head of Staghorn Sumac (Rhus typhina) this time of year, you will find, in addition  to a multitude of seeds, a profusion of scat in the shape of miniscule round, grey balls.  If you’re lucky, you’ll find the larval insect that produced this scat.  Chances are, according to Charley Eisman, author of Tracks and Sign of Insects, that many of the resident insects are in the Gelechioidea family of moths.  The larvae of these moths are consumers of Staghorn Sumac seeds, and judging from the amount of scat usually present, they spend a considerable amount of time inhabiting the seed heads.  It’s likely that Black-capped Chickadees and other birds you see gleaning sumac fruit are actually there  for the larvae as much as the seeds.

 

 


Larvae-seeking Downy Woodpeckers

12-3-11  Larvae-seeking Downy Woodpeckers

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When cooler days arrive and adult insects become relatively scarce, insect-eating birds are very clever at gleaning the twigs, trunks and buds of trees and shrubs for overwintering eggs, larvae and pupae.  Certain galls (abnormal plant growths that house and provide food for a variety of insects) are sought by specific birds.  Downy woodpeckers seek the larvae of the Goldenrod Gall Fly (Eurosta solidaginis), which overwinter inside Goldenrod Ball Galls (formed on Canada Goldenrod, Solidago canadensis) before emerging as adults in the spring.  A tiny1/4” to 3/8”-wide hole (and an empty gall) is evidence that a downy woodpecker had itself a meal!

   


Invertebrate Signs

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A quick look recently at the underside of a wooden bench sitting in the middle of a nearby field revealed a multitude of signs of insects and spiders that sought shelter in this protected spot.  They included the empty chrysalis of a monarch butterfly, the flat, red egg  sac of a Phrurotimpus  antmimic  spider (look closely and you’ll see bumps in the middle  made by the eggs underneath the silk), the silk and twig case of a bagworm moth larva , and a cocoon which is housing the pupa of a moth. 


Naturally Curious wins National Outdoor Book Award

I am delighted to be able to tell you that this morning I learned that NATURALLY CURIOUS won the Nature Guidebook category of the 2011 National Outdoor Book Awards.  I’m honored and humbled by this recognition.   http://www.noba-web.org/books11.htm


Bald-faced Hornet Nest

If you find a  football-size (or larger), gray, papery structure attached to the branches of a tree or shrub, you’ve probably discovered the nest of a bald-faced hornet. (The only other hornets that build a similar nest are aerial hornets, and their nests usually have wider strips, and less of a scalloped appearance than those of bald-faced hornets.)   This structure is actually a nursery, filled with several horizontal layers of hexagonal cells, in which eggs are laid and larvae are raised.  These horizontal layers are surrounded by a multi-layered envelope, which, like the cells, is made of masticated wood fiber from weathered wood such as fence posts and hornet saliva. The different colors reflect the different sources of wood that have been used.  Although only the queen bald-faced hornet survives over winter (in a rotting log or other protected spot), the workers do not die until  freezing  temperatures have really set in, so wait for another month before approaching a nest!

 


Ribbed Petiole Poplar Gall

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If you look at enough Trembling  Aspen (Populus tremuloides) leaves (and to some degree, those of other poplar species), you are bound to come across some that have an oval swelling about the size of a pea where the leaf  and stem, or petiole, meet.  This swelling is a gall – an abnormal plant growth caused by chemicals coming from the moth (Ectoedemia populella) that laid an egg at this spot this past summer, or from the chewing of the hatched larva as it bored its way into the stem of the leaf.  This gall provides shelter and food for the developing larva, which will, after the leaf falls, go down into the ground to pupate.  An adult moth will emerge next  spring.   

 


Some Monarchs Outwit Milkweed

We think of monarch larvae as being impervious to the  ills of milkweed, but they are very vulnerable when it comes to the sticky latex in the sap of their host plant.  The mandibles of young monarch caterpillars are often glued together by this latex, preventing them from eating.  Research shows that about 30 percent of monarch larval loss results from miring  in this glue-like substance.  One strategy young larvae use is to chew a near circle in a milkweed leaf, blocking the flow of latex to the enclosed surface area, which they then eat.  If a monarch survives the first few stages, or instars, of its larval life, it uses yet another strategy to circumvent the latex.  Older, larger larvae often cut through the midvein of a leaf they wish to consume, which dams the latex flow to the entire leaf beyond the cut.  Look for limp leaves as you peruse a milkweed patch.  If you find one, you may be rewarded with the nearby presence of a monarch caterpillar.