Friday, September 19, 2014

Saddleback - Additional Views

An early morning encounter with a Saddleback Caterpillar made me believe that it may be helpful to some if I were to provide a few more images of this remarkable creature.  I’ve been seeing large numbers of this species on a variety of different trees and shrubs.  Those stinging spines suggest how this caterpillar can make a lasting impression on an unsuspecting person.

Each of those spines contains a chemical irritant that makes initial contact with the power of a wasp sting, progresses into a chemical burn and finally settles into an intense itch that lingers for several minutes before dropping to a mild irritation causing brief periods of itching for an additional hour.

The brown and green pattern on this caterpillar makes it difficult to see as it sits feeding on a leaf.  However, once you have a search image in mind, they are pretty easy to locate and avoid.  Unfortunately, it’s usually not the ones you see that give you a sting; it’s the ones hidden from view beneath the leaf that catch you by surprise.  You can easily see the caterpillar to the left, but it’s the one farther down the stem to the right that’s liable to get you.

This is the one that got me yesterday morning.  I was leaning backwards, trying to get a look at a bird in a tree, when my shoulder pressed against the caterpillar.  I think he got me with spines from all four corners.

After rubbing my shoulder and voicing my dissatisfaction with the encounter, I decided to take a few shots of my assailant.  It seemed totally undisturbed by my inadvertent blunder.

The actual head of the caterpillar is located beneath the first body segments and is generally hidden from view.  A ring of spined protrusions protects the head from undesired attention.

This is what you would see if trying to sneak up on the caterpillar from the rear.  Two white spots give the appearance of a menacing creature facing down a potential attacker.  Next year will be a lot of fun if all of these caterpillars live to produce adults in the spring.  

Wednesday, September 17, 2014

Random Caterpillars

I decided to take a couple of hours and conduct a search for caterpillars.  I’ve done that in the past, sometimes with dismal results.  This time I already knew the location of a couple of interesting specimens, so I was sure the search wouldn’t be a total disaster.  Far from being a disaster, my search was more successful than I imagined.  I begin with a species I had never seen before, the Skiff Moth caterpillar. This species looks so much like a leaf blemish that I would have passed it by if I hadn’t previously seen it in photographs.  That’s a Sycamore leaf it is consuming.

On the same Sycamore tree were dozens of these Saddleback Caterpillars.  Those spines are capable of delivering a painful sting.  The caterpillars have the habit of feeding from the underside of the leaves and are often hidden from view.  I managed to confirm the stinging ability of these caterpillars as I maneuvered the leaves in order to get some photos. 

Another with stinging ability is the Black-waved Flannel Caterpillar.  These look very much like a patch of fluff stuck to the leaf.  Head and feet are neatly obscured, but the hair generally points toward the rear where a wispy tail is formed, so you can usually figure out which end ought to be doing the eating.

Not all hairy caterpillars contain stings.  The Banded Tussock Moth may be the most noticeable caterpillar currently roaming Blue Jay Barrens.  I’ve been finding them on every tree or shrub I search.

Banded Tussock Moth caterpillars have a range of color forms from light yellow to dark gray.  I’ve seen half a dozen different colors this year.

On the same Sycamore mentioned earlier, I found several sizes of the Sycamore Tussock Moth caterpillar.

The Sycamore Tussocks also exhibited slight variation in color.  Most showed some yellow, but a few were white.  This is the head end showing the signature eyebrow and whisker tufts.

That Sycamore tree was a treasure trove of caterpillars.  My first sign of caterpillars in the tree was the sound of fras, caterpillar droppings, falling through the leaves.  Unfortunately there were only a few branches low enough for me to reach.  I saw many American Dagger caterpillars resting beneath the leaves, but this was the only one close enough for me to photograph.  Turning the head back toward the body is a characteristic posture for a resting American Dagger caterpillar.

This White-marked Tussock Moth caterpillar has already eaten a large part of the Redbud leaf.  The forward and rear tufts of hair make me think scorpion whenever I see this caterpillar.

The Delicate Cycnia caterpillar feeds on Dogbane.  A patch of Sweetclover that I mowed earlier this summer also contained several Dogbane plants.  Those plants regrew and now have the fresh, young leaves preferred by this caterpillar.

Not all of the caterpillars I found were covered by hair.  I’m still finding Monarch caterpillars on the Milkweeds.  I can’t remember ever having a year where I’ve seen so many Monarch caterpillars.  If Monarchs are doing this well elsewhere, the wintering grounds will be overloaded.

I found this bright little Calico Paint caterpillar feeding on Lance-leaved Goldenrod.  This is an early instar individual and has yet to reach the most colorful stage of its development.

The Checkered-fringe Prominent caterpillar is a leaf edge mimic.  Its body fills in the void left by feeding and gives the appearance of a portion of leaf that has withered due to some unfortunate experience.  This guy fed much more slowly than I’ve come to expect from caterpillars.  Perhaps rapid feeding spoils the mimicry effect.

I found this fellow beneath the leaf of a Persimmon.  This is a Wavy-lined Heterocampa.  Although it is supposed to be very common, this is the first I have encountered. 

I was lucky enough to find an early instar caterpillar that still displayed its antler-like growths.  It’s an attractive caterpillar, but it would have been overlooked had it not been silhouetted by the sun shining through the leaf.

Not all of the caterpillars I found were in perfect health.  This Red-humped caterpillar was on the barn wall a short distance from a hole used by wasps going to and from their nest.  Bodily fluids were leaking from a puncture located about two-thirds of the way back from the head.  It moved very slowly and later fell to the ground.  I suspect it may have been wasp prey that escaped its captor while it was navigating the entrance hole.  It fled the wasp, but was still immobilized by the sting.

Some caterpillars had finished their lives as hosts for various parasites.  This Banded Tussock is nothing but a hollowed shell.

If I carried a ladder with me I might be able to reach some of those caterpillars that feed farther from the ground.  There were several caterpillar-like blobs and shadows high in the trees that were beyond the ability of my eyes or camera to make clearer.  The camera zoom did allow me to extend my reach some, but the results were never great.  I was able to change a gray splotch into a group of early instar Turbulent Phosphila caterpillars feeding on Greenbrier.  I’ll have to check back and see if I can get a better view once these guys have put on some size.

Monday, September 15, 2014

Ants and Scale Insects

If I’m just out looking around, I never fail to investigate anything that draws the attention of the Allegheny Mound Ants.  If the ants are involved, there is undoubtedly something of interest to be seen.

In this case, I was led to a colony of Scale Insects.  Scale insects spend most of their lives immobile on the branch of a tree and create a thick dome-like casing that hides their entire body.  They feed by drawing sap from the tree through a tube shaped mouth that is permanently imbedded into the tree’s bark.  These were feeding on Tuliptrees, Liriodendron tulipifera.  I’m going to go out on a limb here and call these the Tuliptree Scale, Toumeyella liriodendri.

The affected trees were all small and growing out in the open.  A large colony of sap draining insects could cause severe damage to a tree of this size.

Despite their protective covering, Scale Insects are plagued by many predators.  Fortunately for the Scales, the ants are on hand to ward off any potential threats.

Guard duty is not a free service.  It is a benefit resulting from the ant’s actions to protect a valuable source of food.  Like many sap consuming insects, some Scale Insects produce a sugary byproduct called Honeydew that is regularly secreted.  The ants are quick to imbibe this liquid as soon as it becomes available.  The ant on the right in the above photograph has an abdomen distended to a point of semi-transparency by honeydew.

Large Tuliptree Scales found during this time of year are all female.  They are just reaching the end of their year long life cycle and like this one, are soon to die and fall from the tree.  As the immobile females develop, they lose many of their extremities, but the three basic insect body parts are still recognizable.  In the above photo of the underside of a mature Scale Insect, the head is toward the top and the sections of the abdomen are still visible in the lower half of the body.

The female of this species holds the developing eggs inside her body until they hatch.  The newly hatched insects are then held inside the waxy shell until they have developed enough to strike out on their own.  The dark mass to the left is a mass of developing eggs.  Eggs hatch and young are released over a two to three week period.  When the last of the eggs has hatched, the female dies.

The young crawl from beneath the shell and spread out over the tree.  Once they find a suitable site, they will attach themselves to the bark and begin feeding.  The females will never move from that site.  Males will form a shell in which they will pupate next spring. Sometime in early summer, winged males will emerge and search out females with which to mate. 

Females typically grow a dome with a large oval-shaped base.  When conditions get crowded, irregular shapes are formed to fit available space.

The ants have gathered cedar needles and used them to form a temporary shelter at the base of the scale infested tree.  The ants will use this as a base as long as there is honeydew to be collected.

Construction of temporary nests is a common activity among Allegheny Mound Ants.  I’ve seen them make these shelters anything from baseball to basketball sized and use them for weeks or months before once again merging with the main colony.  I have yet to see any activity that gives clues to how the bounty collected by this satellite group is shared with the colony.  I may just have to camp out with the ants until I figure it all out.

Friday, September 12, 2014

Army of Caterpillars - Datana ministra

Now for more hungry caterpillars.  This is Datana ministra, in the same genus as the Major in the previous post.

I found this species feeding on a small Blackjack Oak, Quercus marilandica.  It was evident from quite a distance that this tree had seen caterpillar damage.  Many of the upper branches were left with nothing but stout petioles where there should have been leaves.

The caterpillars are all final instar and have spread throughout the tree.  They are numerous enough to defoliate an oak of this size.  I made a count of nearly 50 individuals and may have missed a few.

Body size and shape is nearly identical to D. major, but the coloration is not nearly as bright.  The body is basically black with several yellow lines.

This species is commonly called the Yellow-necked Caterpillar.  Yellow just behind the head along with this showy orange patch are responsible for that designation.

These caterpillars displayed an interesting feeding strategy.  A pair would team up, with members of the pair working opposite sides of the leaf.  The result is a leaf that still retains its balanced shape.  Many predators search out caterpillars by targeting irregularly shaped leaves resulting from caterpillar feeding activities.  Synchronized feeding helps hide the fact that the leaf is being consumed.

The effects were not always perfect, but the result usually looked much like a naturally formed leaf.

This pairing was not an isolated incident.  Many feeding pairs were found on the tree.

The pair would feed until there was no leaf left and then would back down the petiole and move off to another leaf.

Of course, the plan was not always executed perfectly.  When three caterpillars end up on the end of the same stalk it begins to get silly.  We should stop here before things get out of hand.

Wednesday, September 10, 2014

Army of Caterpillars - Datana major

Caterpillars eat.  Their life is one of consuming and processing food until they move on to the next step of development or are themselves eaten.  Towards the end of summer, when the nights begin to get cool, caterpillars seem to go about their task with an increased sense of urgency.  Most will survive winter as a pupa and they must reach that stage before temperatures get low enough to bring their metabolic processes to a halt.

I imagine there are caterpillars in every tree or shrub you see.  Add to those the multitude of species that feed on grasses and forbs and I doubt that you are ever very far from a caterpillar when in the field.  The trick is in finding them.  This Deerberry shrub is showing signs of the recent dry weather.  Dead leaves are piled beneath the plant and live leaves all show signs of discoloration.  I wouldn’t pick this as the most likely place to find caterpillars, but I always give the Deerberries a check when I’m out.

The view from three feet away reveals what was totally obscured at ten feet.  The shrub is full of caterpillars.  These are larva of the Major Datana Moth, Datana major.  Early instars of this caterpillar are gregarious and feed as a group.  When they reach their final instar, they tend to disperse and feed individually.

It’s hard to imagine such a brightly colored creature blending into its surroundings.  The pattern however, does harmonize with the mosaic of greens, reds and browns in the leaves and the grays and blacks of the stems.  As you come into range, the materialization of the caterpillar image is similar to the moment your eyes reach the proper degree of focus to reveal the subject of one of those 3D Magic Picture prints.  It’s a definite “Ahhh” moment, not to be confused with the more cerebral “Ah-hah”.

The appearance of the caterpillar changes as it moves from one instar to the next.  The individuals with black bodies and broken white stripes represent the final instar prior to pupation.  The brown and white striped caterpillars will soon be proceeding to that final instar form. 

The profusion of cast off skins indicates that the transformation to final instar caterpillars has been a recent event.  These fragile skins are easily dislodged by wind or rain.  In fact, several fell from the branch as I maneuvered it for better viewing.  We haven’t had rain, but the open field in which the Deer Berry grows has experienced an abundance of wind.

Leaves are rapidly disappearing from the  Deerberry.  Dispersal of these larger caterpillars is necessary in order for each individual to feed without disturbance.  The caterpillars have moved out through half of the shrub and a few individuals have arrived on neighboring shrubs.  They will soon make their way to the ground where they will create a chamber in the earth in which to pupate.  Adult moths will emerge next spring to begin the process anew.

The red legs become quite visible when the caterpillars are positioned below the branches.  It’s interesting that so many colorful caterpillars eventually emerge as drab adults.  For some reason, the coloration of these caterpillars makes me think of 1950’s era vinyl patterns.

The hairs on this caterpillar serve no defensive purpose.  When threatened, the caterpillar raises its head and tail with thoracic legs thrust upward like horns.  In addition to the threatening appearance, a bit of ingested material is regurgitated at the mouth and a droplet of liquid is released from the anus.  I’m assuming that both of these substances are unappealing in some way to predators.  The anal droplet is visible in the photo as a honey colored sphere on the end of the upraised tail.  Quite an interesting little creature.