A caterpillar green around the gills, part three

The wasp pupae did not look particularly remarkable, but inside a rapid transformation was taking place. In just one week, the wasps emerged as adults.

The newly emerged wasps gathering on the lid of the vial.

They were, of course, still just as small. Nevertheless, looking closely, it is possible to see that there were two types of wasps. While some of the wasps had typical antennae, the antennae of the other wasps were branched, giving the appearance of delicate antlers.

A view of the wasps from underneath.

The two types of wasps did not mean that the caterpillar host had been parasitized by two different species, however. The two types were males and females. As in some other insects (for example this moth and this mosquito), the more elaborate antennae belonged to the males.

The wasps likely belong to the tribe Eulophini in the family Eulophidae.

Finally, it was time for the wasps to go off in search of their next hosts -- though the one pictured above spent some time inspecting my hand before disappearing into the air.

A caterpillar green around the gills, part two

After emerging from their caterpillar host, the young wasps quickly lost their plump, bright green forms.

Day 1: The wasp larvae (right) emerge from the moth caterpillar (left).

Over the next two days, they first faded to a dull yellow...

Day 2: The wasp larvae begin to pupate.

...and then shriveled and blackened.

Day 3: The wasp larvae have become pupae.

However, the wasps were not sickening and dying -- they were progressing normally through their development from larvae to pupae. Meanwhile, the moth caterpillar that stood by, apparently healthy except for its inertia, had its own development frozen. To be continued...

A caterpillar green around the gills, part one

This Halloween, instead of featuring a seasonable insect or spider, I will share a spooky story of a "possessed" caterpillar.

Parasitoids may be among the smaller enemies that a caterpillar has, but they are also among the most insidious.  When a female parasitoid (generally a small wasp or fly) finds a suitable caterpillar, it lays its eggs on or even inside the caterpillar.  The parasitoid larvae then emerge from the eggs and proceed to feed on the caterpillar.  What becomes of the caterpillar once the parasitoid invasion is complete?  It may be mummified, vanish from inside a fuzzy shroud, or perhaps more strangely -- be left apparently unharmed.

A copper underwing (Amphipyra pyramidoides) caterpillar and recently emerged parasitoid wasp larvae.

The light green caterpillar shown above and below is surrounded by the darker green larvae of a parasitoid wasp.  The wasp larvae had recently finished feeding inside the caterpillar and had broken through the sides of the caterpillar to finish their development outside.

The slits that the wasp larvae emerged through are visible behind them.

Meanwhile, the caterpillar just sat there as if unperturbed by the litter of parasitoids.

However, the caterpillar was hardly passive.  When the parasitoid larvae were threatened by an approaching object, the caterpillar became surprisingly aggressive.

The parasitoids had left the caterpillar alive, but not at liberty.  Though the caterpillar was no longer needed as food, it could still be manipulated into serving as the parasitoids' protector.

To be continued... but in the meantime, you can explore some more: Parasitoid Increases Survival of Its Pupae by Inducing Hosts to Fight Predators

On the safe side

When feeding in a large group, caterpillars may be more noticeable to predators -- but they may also be better able to defend themselves.  Groups of tent caterpillars and webworms can consist of hundreds of individuals, which makes them easily spotted (and probably smelled) even from a distance. To thwart their many enemies, these caterpillars surround themselves and their feeding zones with a protective netting of silk.

A nest of fall webworms (Hyphantria cunea) on a mulberry branch.

The caterpillars then proceed to devour nearly everything within their tightly woven nest.  As they move along a branch, all that they leave behind are leaf skeletons wrapped in silk.

The larvae can completely skeletonize large leaves.

Meanwhile, any predators that locate the caterpillars are likely to depart without obtaining a meal. Watch a wasp get foiled by the silk enclosure in the video below:

Springing to life, part one

Just in time for the first days of spring, the Texas bluebonnets spread from sparse glimpses of blue to cover all the nearby meadows.

A field of Texas bluebonnets (Lupinus texensis) in bloom.

Though the bluebonnets were not yet swarmed with visitors (the way they were last spring at the peak of their bloom), I found a variety of insects on the blossoms, including honey bees, lady beetles...

A seven-spotted lady beetle (Coccinella septempunctata) on a bluebonnet inflorescence. 

...and even large, menacing wasps.

A paper wasp (Polistes sp.) feeding from bluebonnet flowers.

However, the many butterflies that also appeared with the mild spring weather were mostly attracted to another type of flower.  To be continued...

Falling back

Spiders can be predators of wasps, but sometimes the relationship is reversed and the spider becomes the prey.  This summer I watched a dramatic encounter that unfolded too quickly for me to capture on camera.  A spider was sitting on a leaf at the end of a tree branch while a large wasp hunted nearby.  As the wasp drew near, the spider edged away and then dropped down a thread to hang in mid-air.  For a few moments, it appeared that the spider had escaped the wasp's attention -- but then the wasp struck.  I had a brief glimpse of the wasp and spider grappling each other before they plummeted to the ground.  By the time they landed, the spider was already paralyzed or dead.

Not all spiders are so easily subdued, however.  Take, for example, the black-and-yellow argiope, one of the largest orbweaver spiders in North America (along with the giant lichen spider and the golden silk spider).

A black-and-yellow argiope (Argiope aurantia) orbweaver spider.

As I was photographing this very imposing spider, a wasp came up and hovered to inspect the spider too.

A wasp approaches the orbweaver spider.

If the disparity in size wasn't already enough to discourage the wasp from taking further action, a wave of the spider's legs seemed to complete the message.

The orbweaver spider waving its legs.

The wasp retreated, leaving the spider undisturbed.

A taller tail

Wasps with "stingers" the size of hypodermic needles may sound like the stuff of nightmares, but they are quite real.

A giant ichneumon wasp (Megarhyssa nortoni quebecensis).

Happily, they are also quite harmless (at least to people).  Their needle-like "stingers" are used for laying eggs, not injecting venom.

A size comparison.

The ovipositors (literally, "egg placers") of giant ichneumons are so disproportionately long because of where their eggs need to go.  Giant ichneumons, just like their more modest relatives, are parasitoids of other insects.  The unusual challenge they face is that their hosts, the larvae of horntails (a.k.a. wood wasps), feed deep within wood.  To reach them, female giant ichneumons must pierce directly through the wood with their ovipositors.

The giant ichneumon searching for signs of larvae below.

However, first the wasps must complete another difficult task -- locating their hosts within the wood.  The wasp that I watched spent some time circling around and feeling the wood with its long antennae, but it appeared that there were no horntail larvae in reach.

The vanishing act

The monarchs were not alone in facing danger in the garden this winter.  On the papaya, there were signs that Alope sphinx moth (Erinnyis alope) caterpillars had been chewing on the edges of the leaves.  However, the caterpillars themselves were nowhere to be seen.  These caterpillars can be well camouflaged against papaya leaf veins, but in this case the caterpillars were not simply disguised.  The caterpillars were gone, and in their place, something else was lined up along the leaf veins.

A ball of white fuzz along a papaya leaf vein.

On several of the papaya leaves, there were fuzzy white objects.  Although the objects were roughly cocoon shaped, they were obviously not the cocoons of the sphinx moths (which pupate on the ground).  Looking from another angle, I could tell that the white fuzz was hollow inside -- just as if it had been made around a caterpillar.

The hollow center of the white fuzz.

Indeed, it looked that way because it had been shaped around a caterpillar.  Parasitic wasp larvae had eaten the caterpillar and then spun their own cocoons within a fuzzy matrix around the quickly disappearing remains of their host.  In a previous year, we kept some of this white fuzz in a jar to find out what was inside; the result was a jar full of tiny black wasps!

Explore some more: Erinnyis alope life cycle

Going for a ride? Take a Beetle or a Vespid!

Since I am sitting in an airport, it seems like a good time to write about travel.  Though insects seem small from our perspective, many of them are able travelers.  They can cover long distances by walking, jumping, swimming, digging, and flying.  Additionally, they can use their sensitive antennae to detect faraway food (such as carrion, in the case of the burying beetle shown below).

A tomentose burying beetle (Nicrophorus tomentosus) attempting to scurry away from the camera.

These characteristics make insects an attractive mode of transport for a group of much less mobile arthropods: mites.  If you look closely at the burying beetle below, you can see the mite that had crawled out from some hidden spot onto one of the beetle's wing covers (elytra).

A mite (Poecilochirus sp.) riding on the back of the tomentose burying beetle.

Poecilochirus mites are commonly found riding on burying beetles, since these mites also need to get to carrion in order to feed.  Some Poecilochirus mites consume fly eggs and larvae on the carrion, while some are predators of the burying beetles' own eggs.  Meanwhile, other mites prefer foods unrelated to carrion and, correspondingly, take different forms of transport in search of those foods.

A group of mites rides on the back of the thorax of a mason wasp (Vespidae).

Are mites at best hitchhikers or free riders?  Perhaps not, as some evidence suggests that insects can benefit from the mites too.

Explore some more: Parasitic mites as part-time bodyguards of a host wasp

More than a pain in the neck

Since beetles are well defended against spiders by their tough exoskeletons, I was curious how Japanese beetles were falling victim to the candy stripe spiders.  However, each time I found a Japanese beetle and a candy stripe spider together, I had already missed the decisive moment.  Therefore, I was limited to reconstructing events by inspecting the aftermath of the beetle-spider encounters.

A Japanese beetle (Popillia japonica) being eaten by a candy stripe spider (Enoplognatha ovata, ovata color morph).

While watching the spiders consume their prey, I noticed that they were exploiting a weakness in the beetles' defenses.  Like human armor, beetle exoskeletons are vulnerable at the joints.  In the pictures above and below, you can see that each spider has bitten between the beetle's head and its sternum (where the beetle's neck would be if it had one).  Though these spiders had already moved on to feeding, the same spot seems a likely target for the killing bite.

Another Japanese beetle being eaten by a candy stripe spider (Enoplognatha ovata, lineata color morph) in 2012.

Going back through some of my other photographs of the candy stripe spiders, I found that the strategy of "going for the throat" also appears to be effective with other difficult types of prey, such as wasps.

A female candy stripe spider (Enoplognatha ovata, redimita color morph) with a wasp.

A dirty job

On the same excursion during which I encountered the strangely attractive crab spider, a fellow walker called my attention to a wasp that was on the path.

A mason wasp (Eumeninae) collecting mud from the ground.

The ground was still moist from rain in the previous days and the wasp appeared to be digging in the mud with its mandibles.  Then, as I was pressing the shutter button of my camera, the wasp suddenly took flight.  By chance, the wasp and the mud ball it was flying off with were caught in the picture.

The mason wasp flies off with the mud ball held in its mouth.

What could a wasp do with mud?  It could build the walls of a nest!  I had seen similar wasps around the house which had done just that.  The wasps had constructed their mud nests in crevices and had progressed to provisioning the nests with food.  In the picture below, you can see a mason wasp's nest in the frame of one of our windows.  Just inside the entrance to the nest, part of a green caterpillar (a.k.a. food for the wasp's offspring) is still visible.

The nest of another wasp, complete with a green caterpillar to feed the wasp's offspring.

Long live the queen butterfly

Although one encounter with a parasitoid wasp ended without incident, the queen caterpillars (Danaus gilippus) were not out of danger.  As I was looking over my pictures from the previous day, I noticed another wasp -- sitting on top of the largest of the queen caterpillars.

A queen caterpillar (Danaus gilippus) and a parasitoid wasp.

If you have trouble finding the wasp in the picture above, look between the 5th and 6th yellow stripes from the left, or just look at the close-up below.

A close-up of the parasitoid wasp on the queen caterpillar.

In the subsequent pictures that I took (which unfortunately are not focused on the wasp), the wasp's abdomen is curved down and the wasp appears to be ovipositing (laying eggs) into the caterpillar.  After inspecting this series of pictures, I decided to monitor the caterpillar closely for any sign that it was indeed parasitized.  However, the next morning, the caterpillar had disappeared from the milkweed.  By searching the surrounding area, I eventually located the caterpillar in a sheltered spot where it was beginning its transformation into a pupa.

The queen caterpillar preparing to pupate.

One day later, there was a very healthy-looking chrysalis where the caterpillar had been.

The chrysalis of the parasitized(?) queen caterpillar.

Over the next few days, the chrysalis continued to look as it should, without any dark discoloration to suggest that there were a couple hundred wasps developing inside instead of a butterfly.  I left Florida before I could be sure what the result would be, but I have been informed that in the end the wasp's attempt failed and it was a butterfly that emerged from the chrysalis.

This is a different queen butterfly (Danaus gilippus), since I didn't get to see the one that emerged from the chrysalis.

Royal parasite

Many plants protect themselves from herbivory with toxic chemicals.  However, some herbivores not only tolerate these compounds, but also actively sequester them to become distasteful themselves.  For example, caterpillars such as monarchs (Danaus plexippus) and queens (Danaus gilippus) prefer to feed on milkweeds, which contain toxic cardiac glycosides.  Nevertheless, this dangerous diet does not deter all the caterpillars' potential enemies.  One day when I went to check on the caterpillars, I found a parasitoid wasp roaming the milkweed plant.

A parasitoid wasp on a milkweed stem.

With its antennae twitching up and down, the wasp walked along the milkweed stem...

The wasp walking along a stem above a queen caterpillar.

...and gradually closed in on one of the queen caterpillars.

The wasp perched directly above the queen caterpillar.

When the wasp reached the end of the stem, it appeared poised to descend and parasitize the caterpillar.  Yet, anticlimactically, the wasp flew off and the caterpillar continued eating the milkweed in peace.

Saved by the camera

I was standing near the crabapple tree when a dark shape on one of the leaves caught my eye.  As I moved closer, I saw that there were actually two dark shapes -- a parasitoid wasp and a jumping spider. 

A jumping spider sneaking up on an ichneumon wasp.

The jumping spider was stalking the parasitoid wasp, which was preoccupied with laying an egg.  With the spider poised to strike, I thought the wasp had no chance to escape.

The jumping spider closes in on the ovipositing parasitoid wasp.

Mysteriously, though, this was as close as the spider got.  After looking at the wasp for a couple of seconds, the spider abruptly turned and moved back down the leaf.  Perhaps it was spooked by the camera, or perhaps the wasp was simply too large for the spider.  Meanwhile, the wasp continued laying its egg.  A couple of minutes later, it turned to face the site where it had been laying an egg or eggs, then spent some time apparently chewing.

The ichneumon wasp chewing nearby its oviposition site.

Once the wasp had flown off, I turned the leaf over to see what had been parasitized.  What I found was the mine of a tentiform leaf miner, with a hole where the wasp had been facing.

A tentiform leaf miner mine with a hole (on the left) where the wasp appeared to be chewing.

The seed defenders

Many seed predators have converged upon the hollyhocks and are feasting on the seeds.  Nevertheless, things may not be as bad as they first appear for this new generation of hollyhocks -- for the seed predators have been attracting enemies of their own.  During my rounds through the garden, I have noticed that the hollyhock seed pods are also routinely patrolled by a number of predators.  The most common of these predators are wasps and ladybugs.

A European paper wasp (Polistes dominula) on a hollyhock seed pod.

A ladybird beetle (Coccinellidae) inside a hollyhock seed pod.

Although many of the hollyhock seed predators that I have seen are bugs, not all of the bugs on hollyhocks are necessarily there to eat seeds.  When I first saw the bug pictured below, I thought it was piercing through the pod to reach the seeds inside.

A bug eating a much smaller insect, speared on its mouthparts.

Upon close inspection, however, a very small insect is visible at the end of the bug's mouthparts.  In contrast, the bug pictured below was no longer a predator of any kind.  Instead, it had become the prey of a crab spider.

A crab spider (Mecaphesa sp.) eating a bug on a hollyhock seed pod.

Whatcha doin', hibernating?

Ever since I moved in, there has been an old fence post leaning against the back of the house.  I recently tried to move it -- only to be surrounded quite suddenly by about five wasps (I didn't stay to count).  From behind the safety of the glass door, I watched and waited until the air was clear of wasps again.

I hadn't seen a nest on or underneath the fence post, so where had the wasps come from?  I went back at night (when I thought the wasps would be less likely to become agitated) to look more closely. 

A group of European paper wasps (Polistes dominula) huddled together between the fence post and the wall.

The wasps had returned to the fence post and were huddled in a tight group.  This time, I was able to identify them as European paper wasps (Polistes dominula), which I had also found nesting along the fence.  These wasps spend the winter hibernating off the nest, so it seems likely that this is what the wasps were doing -- although it is still summer.

The wasps don't appreciate being disturbed.

Hibernating or not, the wasps were a bit too aware of my presence for my comfort.  That fence post may have to stay where it is for now!

Trespassers will be stung

Whenever I linger too long near the garden gate, I start to get the feeling that I ought to move on.  This feeling arises around the time that a wasp flies up to inspect me.  If I don't immediately respond to the impulse to flee the area, the wasp circles menacingly -- and the impulse grows almost unbearable. 

These "guard" wasps are European paper wasps (Polistes dominula) and they have built several nests on the fence, including right next to the hinges of the gate. 

A European paper wasp (Polistes dominula) guards its nest.

The wasps sitting on the nests are very attentive to anything moving nearby.  Thankfully, the one in the video below stayed on the nest to defend it, rather than flying up to attack.

* To see this video in high definition (1080p), you may need to (1) click "YouTube" to watch on the YouTube website and (2) change the settings at the bottom of the video screen.

When I approached the larger nest, all three wasps turned to watch me.  Unlike at the previous nest, one wasp looked like it was preparing to take flight.  I took this as a signal that I should retreat.  In order to get a better look, I had to come back at night, when the wasps were less easily agitated.

European paper wasps (Polistes dominula) on their nest at night.