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...

More than an itch, part three

For most insects, tiny bug nymphs pose a negligible threat.  The threat is hardly increased when the nymphs are in a group (which they often are).  However, unlike the beetle being assailed by the stink bug, there are some potential victims that lack the mobility to attempt an escape.

A group of bright red bug nymphs (Largus sp.) feeding on a white object.

The group of bug nymphs pictured here had located one such immobile victim on a leaf.  In order to see what they had found, I blew air at them.  The nymphs quickly scattered across the leaf, revealing a while cocoon.

The bugs scatter revealing a cocoon.

Nearly as quickly, the bug nymphs began to return to the cocoon and to resume feeding on whatever had been developing inside.

The bugs begin to return.

All sewn up, part three

After sealing itself up inside the hydrangea leaves, what did the hydrangea leaftier caterpillar do?  From the outside, there was no obvious sign that the caterpillar was feeding on the leaves.

Hydrangea leaves after an encounter with a hydrangea leaftier (Olethreutes ferriferana) caterpillar.

Pulling apart one of the older leaf capsules to see what was happening inside, I found something that did not look very much like a caterpillar.

Nested inside the sealed leaves was a sealed bundle.

It looked a lot like a clump of moldy frass, but I tried separating it anyway -- and out popped a twitching pupa.

Inside the cocoon was a hydrangea leaftier (Olethreutes ferriferana) pupa.

By tying the hydrangea leaves together and then forming a cocoon inside, the caterpillar had made a snug refuge with multiple layers of security to protect it during its metamorphosis into a moth.

Caterpillars on the grass, part four

By the time fungus-infected caterpillars crawl up to the tops of grass stems  (or to other elevated positions), they are almost certainly doomed.  Therefore, it might seem reasonable to assume that this 'height seeking' behavior is instigated by and for the benefit of the fungus.  Yet, there is another possibility.

Though it is too late for the dying caterpillars to save themselves, they may be acting to save their relatives.  Female moths and butterflies sometimes lay their eggs in clumps, with the consequence that sibling caterpillars develop in close proximity.  For these families, it would be advantageous if diseased individuals left the group to avoid infecting the others.  Furthermore, being stuck at the top of a grass stem may have significant drawbacks for the fungus if large herbivores or predators of the caterpillars are around.

Whether climbing up grasses was more beneficial for the caterpillars or the fungus, there were some caterpillars that avoided infection.  About the same time and in the same area that I found the sick, green caterpillar, I caught a much healthier version that had been crawling across the ground.

A healthy moth caterpillar.

I took the healthy caterpillar home to observe whether it too would fall victim to the (at the time) mysterious epidemic.  However, unlike the sick caterpillar, which was rapidly engulfed in fungus, the healthy caterpillar soon metamorphosed into a pupa...

A healthy moth pupa.

... and later emerged as a nondescript, grayish brown moth.

The fallen monarchs

Last winter, we found a monarch chrysalis that had fallen to the ground.  We brought it inside and several days later the story ended happily as the monarch successfully emerged and took flight.  This winter, falling was still a danger -- my mother found two chrysalises on the ground -- but there were also more serious threats lurking in the garden.

The remains of a caterpillar that had begun to form a chrysalis.

When I arrived in Florida and surveyed the garden, the only monarchs that I found were a caterpillar that had died while metamorphosing into a chrysalis (possibly due to disease or parasitism) and a chrysalis that did not look much healthier.

Something seems to have gone wrong for this monarch chrysalis.

The chrysalis was a dark brown color instead of bright green.  Although a healthy monarch chrysalis should turn dark shortly before the butterfly emerges (see here), something was wrong in this case -- the monarch's wing pattern was not visible.

A few days later, the chrysalis was still intact... but empty.

After a few days, the chrysalis was hollow with no obvious sign of what had happened to the butterfly that had been developing inside.  Meanwhile the chrysalises that my mother had rescued from the ground were also brown and hollow.  What had happened to all the monarchs? 

Pupae (left) from the flies that parasitized this monarch chrysalis (right).

Looking in the container below the rescued chrysalises, we found several pupae. These pupae belonged to flies -- flies that had parasitized the chrysalises and then emerged instead of the butterflies.  Unfortunately, since the container was not sealed, the adult flies had already escaped.

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.

Cleaned out of house and home

When some of the spotted oleander caterpillars (Empyreuma affinis) looked large enough to leave the oleander tree, I decided it was time to clean away the old, empty cocoons from the surrounding area.

Spotted oleander caterpillar (Empyreuma affinis) cocoons in the corner of a window frame.

I wanted to be able to keep track of the new pupae, but I couldn't do that very easily with tens of cocoons from past generations filling every nearby sheltered spot.  However, I acted a bit too late -- there were already a few new pupae hidden among the old cocoons.  Some were already several days old...

Spotted oleander caterpillar (Empyreuma affinis) pupae.

... and one was still being formed.

A brand new pupa of a spotted oleander caterpillar (Empyreuma affinis).

I kept the pupae in an enclosure and for several days saw no change, except that the youngest pupa darkened to match the rest.  Then, one morning, two of the moths emerged.  Unlike my recent experience with the monarch butterfly, there was no sign (that I could recognize) that the moths were about to emerge; thus, I missed both events.  Later that day, we took the moths to the oleander tree and released them into the open.

The first stop for this recently emerged spotted oleander caterpillar (Empyreuma affinis) moth was my mother's leg.

The moths showed no interest in their host plant, and in this they were exactly the same as the monarch butterfly.  Although one of the moths did rest briefly on my mother's pants (as shown in the picture above), they were both soon headed high up into the trees.

One of the moths resting on a palm frond after its first extended flight.

Rapid hair loss

In addition to being toxic, spotted oleander caterpillars (Empyreuma affinis) are covered in tufts of hairs that look like they could deliver a painful sting.  Some related species do indeed have stinging (urticating) hairs.  Thus, it seemed safest to avoid touching these caterpillars.

A spotted oleander caterpillar (Empyreuma affinis) climbs up a wall to find a place to pupate.

Whether the hairs sting or not, one way that they are used by the caterpillars is in their cocoons.  As a caterpillar spins a loose silk cocoon around itself, its hairs fall out and become incorporated in the cocoon.

A spotted oleander caterpillar (Empyreuma affinis) in its cocoon of silk and hairs.

Once the caterpillar pupates, only a few hairs are left attached to the shed skin (which can be seen to the left of the pupa below).

The early pupa, before it has darkened.

The hairs in the cocoons do not seem to provide protection for the pupae, however.  While clearing away some old cocoons and searching for any intact pupae among them, I ended up touching quite a few hairs without getting stung.

Searching high but not low

Two weeks ago, I found two green caterpillars in front of the house.  I put one in a jar to observe, but left the other.  This second caterpillar had been climbing up the house and had made it about three feet off the ground.  I thought that it must have kept climbing, but I did not see it anywhere higher up on the house when I went back to look for it again.  The caterpillar had vanished, and I turned my attention to other things.

This Saturday, it was sunny, relatively mild, and the ladybugs were out again.  I was crouching down to see how many ladybugs I could spot, when I noticed an incongruous shape near the bottom of the siding.  Taking a closer look, I saw that it was a chrysalis just like the one I had in a jar, but still green.

A small cabbage white butterfly (Pieris rapae) chrysalis on the house siding.

Since I had only been looking for the caterpillar higher up on the house, I don't know whether this chrysalis was made by the caterpillar I saw two weeks ago or by a more recent arrival.  Perhaps more time -and a color change- will tell.

Out of the gall and into the jar

When I opened the thistle gall, I exposed four Canada thistle stem gall fly (Urophora cardui) larvae. These flies can reduce the seed production, and thus the spread, of the invasive Canada thistle (Cirsium arvense).  Therefore, I decided to give the larvae a new home to replace their broken gall.  I put them into a jar, but had trouble deciding where to keep the jar.  I worried that the jar might not provide as much insulation as the gall, and thus that the larvae might freeze if kept outside.  However, inside the house it was warm; would the larvae take this as a cue that spring had arrived and pupate several months early? 

A larva (left) and three pupae (right) of the Canada thistle stem gall fly (Urophora cardui).

Five days later, three out of four of the larvae have pupated.  Perhaps their pupation was just triggered by the destruction of the gall, but I think it is likely that the warm temperature inside the house played an important role.  The next stop for the jar is the garage, where I hope the cooler temperature will halt their development until a more appropriate time.

Before and after

Over the last few days, there has been a slow development in my waiting game with the chrysalis.  At first, the coloration of the chrysalis matched that of the caterpillar it had been: green with yellow spots.  Gradually, the green has been replaced by a gray remarkably similar to that of the stick I put in the jar with the caterpillar.  Although this may be just a coincidence, some species can camouflage themselves by matching the color of the chrysalis to its surroundings.

Explore some more: Butterfly Pupae in Living Color

Waiting game

This summer, I was excited to find that a painted lady butterfly (Vanessa cardui) had made its chrysalis on the house.  I visited it several times a day, hoping to catch the moment when the butterfly would emerge.

The painted lady butterfly (Vanessa cardui) chrysalis that I observed in Maine in July.

Then, one morning, I went to check on the chrysalis only to find that it was completely gone -- not even the empty shell was left.  I was unhappy that I had missed my chance to see the butterfly emerging, and worse yet, that the chrysalis might have been eaten by a predator before the butterfly had completed its development.

Last weekend, I came across another chance to observe a butterfly (or perhaps a moth) emerging.  At the front of the house, there were two green caterpillars.  These caterpillars were on the move (one climbing up the house and the other crawling along the hose), which suggested to me that they had finished eating and were searching out places to pupate.  Given my experience over the summer, I decided that this time I would go about things differently.

One of the caterpillars that I found in the garden last weekend.

I collected one of the caterpillars into a jar, gave it a stick to climb on, poked holes in the lid... and waited.  Two days later, it pupated, forming an interesting-looking chrysalis.

Two days later, the caterpillar had turned turned into a pupa.

Now I am waiting again, but with much better odds of success.