Friday, August 31, 2012

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!

Wednesday, August 29, 2012

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.

Monday, August 27, 2012

Seeing the spider for the eggs

Not all eggs stuck on plants are difficult to identify.  Determining what laid them is simple when the mother is still there -- as long as you notice her.

I first saw the egg sac pictured below from across the yard.  The white of the spider silk stood out brilliantly against the brown of the plant stem.  As I got closer, I could see the contours of the individual eggs neatly wrapped within the silk. 

A spider egg sac attached to a plant stem.
I wondered what kind of spider had laid them, but deciding that I wouldn't be able to identify them until they had hatched, I began to inspect the seeds on the neighboring stems.  When I looked back at the egg sac from a different angle, I was surprised to find that a rather large spider was standing guard over the eggs. 

The female spider guarding her eggs.
Of course, she had been there all along (as you may have noticed from the first picture).  I had been so focused on the bright white egg sac that I had ignored all the surrounding brown.  I was lucky that on this occasion I had decided to leave the eggs where they were.  If I had attempted to collect these eggs to raise in a jar, I might have gotten a bite instead!

Friday, August 24, 2012

A tall tail

How do wasps get their eggs inside other insects? First, the female wasp must find its host insect. This task may not seem difficult when the host is large and out in the open. However, many wasps parasitize insects that live deep within plants. The hosts of the wasp featured in this video are burdock seedhead moth (Metzneria lappella) larvae.

* 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.

To detect the moth larvae feeding within burdock flower heads, the wasp (Agathis malvacearum) uses its sensitive antennae. Once a host has been located, the wasp pierces through the flower head and into the larva with its long ovipositor (from Latin, the "egg placer"). Although the ovipositor resembles a giant stinger, it is used to inject an egg rather than a painful dose of venom.  In fact, the stingers of other wasp and bee species are modified ovipositors; thus, only the females are capable of stinging.

Thursday, August 23, 2012

The egg snatchers

Summer is ending and there are fewer flowers blooming in the garden.  As a result, the foliage gets more of my attention.  It may not be changing color yet, but it is covered with insect and spider life.  Earlier this week, I noticed several clusters of small eggs on lamb's ear (Stachys byzantina) leaves and on grass.

I was curious to know what had laid all these eggs.  Although most of them had already hatched, I did not see any insects nearby nor any damage to the leaves from hungry young insects.  Therefore, when I found a cluster with about half the eggs still unhatched, I decided to keep the eggs in a jar and observe what emerged. 

The leaf and eggs in my "incubation chamber": a jam jar with a damp paper towel.
The next morning, I saw my first hatchling -- but it was not the offspring of whatever had laid the cluster of eggs.  Instead, it was a parasitoid wasp.  Some time ago, this wasp must have hatched from an egg laid inside one of the already small eggs visible in the picture below.  It then grew, consuming the insect that was developing in the surrounding host egg. 

A parasitoid wasp emerged from one of the eggs.
Two more days have passed and the first wasp has been joined by several more wasps.  Nearly all the eggs have hatched, but I am no closer to finding out what laid them!

Monday, August 20, 2012

The pincer attack

Despite the fact that they have never done me any harm, I have always had a strong dislike of earwigs.  Their large pincers are threatening enough without the suggestion that they could be brought into my ears.  My insect field guide asserts that though earwigs do seek refuge in enclosed spaces, those spaces do not include human ears. 

A European earwig (Forficula auricularia) deep inside a hollyhock (Alcea rosea) flower.
Whether earwigs really do crawl into ears is not something I am willing to test for myself.  However, I was willing to test how much of a pinch the pincers can give -- as long as I wasn't the one getting pinched.  Watch the video below to find out what happened.

* 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.

I was somewhat disappointed with the response of this European earwig (Forficula auricularia).  Although the earwig did use its pincers to grapple with the grass stem, it did not seem to do any serious pinching.  What was more impressive was that the earwig barely paused chewing on the hollyhock (Alcea rosea) leaf as it fended off the attack.

Friday, August 17, 2012

It's a bird... it's a plane...'s a sphinx moth!

This sphinx moth is aptly, if somewhat unimaginatively, called the Hummingbird Clearwing (Hemaris thysbe).  Like a hummingbird, it beats its wings rapidly, hovering by a flower for a moment, then abruptly darting off to the next flower. Although the number of legs, the number of wings, the proboscis (the mouthparts, shown coiled in the picture above), the antennae, etc. give it away in a photograph, as it flies, it can easily be mistaken for a hummingbird.

The wings of the Hummingbird Clearwing (Hemaris thysbe) seem to disappear as it hovers.
Even in bright light and with the flash, the wings frequently moved too fast for the camera shutter.  The wings also seem to disappear in the photographs because, as the moth's name suggests, they have large sections that lack scales and are transparent.

A Hummingbird Clearwing (Hemaris thysbe) hovering while drinking nectar from a flower.

Wednesday, August 15, 2012

Insects beware: here be spiders

My backyard has been looking very dry and brown from the summer heat.  Not hoping for much, I went out in search of life.  A few plants are still blooming and I was very pleased to see a small crab spider on one of the first flowers I checked. 

A crab spider and ladybug on a common hollyhock (Alcea rosea) flower.

Then there was another... and another.  On the bush pictured below, I found a tiny crab spider on almost every flower!

A tiny crab spider sits between the two petals on the right side of the flower.
I watched in suspense as a small bee visited one of these flowers.  However, just as for a previously featured crab spider, the little crab spider on this flower posed no threat for the bee.  The real danger for the bee came immediately after it left the flower -- and flew straight into a funnel-web.

A funnel-web spider eating a small bee.
The funnel-web spider, responding to the motion of the web, sprang up at the bee -- but missed.  The bee managed to force its way through the web and then sat on a nearby leaf for a few moments, grooming off the bits of web that had come with it. (The bee being eaten by the funnel-web spider in the photograph was an earlier catch.)

I then decided to check the front yard.  There it was the same: spiderlings everywhere. 

A tiny crab spider sitting on an aster and eating something even smaller.
The little one pictured above had found something even smaller to eat.  It won't be very long, though, before some of the dozens of young crab spiders have grown large enough to hunt bees.

Monday, August 13, 2012

This flower isn't big enough for both of us

Even when there isn't a crab spider lurking in ambush, a flower can be a rough spot for a bee.  Nectar and pollen are often in short supply and competition for these limited resources can be intense.  Bees start foraging very early in the morning (as long as it is warm and clear), but this is not enough.  Once a bee finds a rewarding flower, it must defend against newcomers that would poach its hard-sought prize.

Two bumble bees (Bombus spp.) competing for space on a flower kick at each other.

The coneflower (Echinacea sp.) pictured above wasn't big enough for the two bumble bees (Bombus spp.), which kicked out at each other until one abandoned the flower.  To see the full action of another bumble bee kick-boxing match, watch the video below.

* 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.

Friday, August 10, 2012

A tale of two nests

Three weeks ago, I wrote about two bird nests we had found in the bushes.  One had four eggs and the other had only two.  What has happened since that post? 

Every few days, I would take a quick peek into each nest to see if anything had changed.  A couple of the times that I searched the dense shrubbery for the nest with four eggs, I was startled by a shiny black eye staring back at me.  The parent, a song sparrow (Melospiza melodia), was incubating the eggs.  Then, one day, there were no longer four eggs -- but four almost featherless chicks.  Although their eyes were not yet open, they would open their beaks wide at any movement above the nest. 

Four very young song sparrow (Melospiza melodia) chicks.
Meanwhile, the parents were busy catching insects to feed to the hungry chicks.  Just like the Eastern Phoebe parents, the song sparrows would not approach the nest when we were nearby.  Even if one had caught a juicy insect (as in the video below), it would wait until we were no longer visible before darting into the bushes to deliver the food.

 * 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.

The four chicks grew surprisingly quickly and my mother reports that they have already left the nest.  She has heard them chirping from the undergrowth some distance from the nest and seen the parents watching from the trees.

The other nest, with two eggs, had a very different story.  Although I had originally hoped that more eggs would be added, every time I looked there were still only two eggs.  Moreover, the eggs were never being incubated.  It seems that the nest was abandoned by the parents, or perhaps worse -- I had also found signs of an owl in the vicinity of the nest.

Thursday, August 9, 2012

The painted lady in distress

At the butterfly garden, monarchs weren't the only butterflies to find their favorite plants.  Painted lady butterflies (Vanessa cardui) had also been attracted to the garden and were busy drinking nectar from the many flowers.

Painted lady butterfly (Vanessa cardui) drinking nectar from a coneflower (Echinacea sp.).
Whereas monarchs specialize on milkweed, painted ladies prefer thistle (in fact, they are also known as 'thistle caterpillars').  Even when small, the caterpillars can be located easily due to the white silk 'tents' that they weave around themselves.  Once a caterpillar has eaten enough thistle, it forms a chrysalis and begins its metamorphosis into a butterfly.

Painted lady chrysalis (Vanessa cardui) hanging on a thistle, surrounded by silk webbing.
However, the tent does not protect the chrysalis from all enemies.  I found one chrysalis swaying in a gust of wind.  I waited until the wind died down so that I could get a better picture.  Surprisingly, even when the wind stopped, the chrysalis was still shaking violently.  Looking more closely, I saw that there was a small wasp sitting on it.

Painted lady chrysalis (Vanessa cardui) being parasitized by a chalcid wasp.
It was the touch of this wasp, a parasitoid of the painted lady, that was causing the chrysalis to shake.  If the wasp succeeded in laying its eggs despite the shaking, then in a few days it will be a new generation of wasps, not a butterfly, that emerges from this chrysalis.

Explore some more:
Charlotte Rhoades Park and Butterfly Garden

Tuesday, August 7, 2012

Summer in the city

This weekend I visited my brother in Portland, Oregon.  Much of the year, Portland has a cool and rainy climate -- but not this weekend!  Instead, there was a record breaking heatwave, with a high temperature above 100°F.  During the hottest part of the weekend, while more sensible people were taking shelter in whatever cool spot they could find, I explored my brother's backyard.  

Not much was stirring in the unusual and oppressive heat.  Most of the insects I found, such as the leafhopper pictured below, were hiding in the shade.

A leafhopper hides in the shade of a leaf.
The only ones keeping busy were the bees!

A honey bee (Apis mellifera) drinking nectar.
A bumble bee (Bombus sp.) foraging.

Friday, August 3, 2012

Got milkweed?

In our own garden, there haven't been many butterflies this summer.  Although there are many flowering plants, these have been attracting mainly bees and flies.  The times that I have seen butterflies, they were just passing through the garden.

To see more butterflies, we took a trip late one afternoon this week to a public garden that is designed to attract butterflies -- especially monarchs.  How does a garden attract monarchs?  With milkweed, lots and lots of milkweed.

A monarch butterfly (Danaus plexippus) drinking nectar from a milkweed flower.
Adult monarch butterflies come to milkweed flowers to drink nectar.  The female butterflies will also lay their eggs on milkweed plants.  I looked under many leaves, but I didn't find any eggs. What I did find was a multitude of monarch caterpillars and a couple of chrysalises.

A monarch caterpillar eating a milkweed leaf.
A monarch chrysalis.
Why are monarchs so attracted to milkweed?  Milkweeds contain a toxic chemical that the caterpillars ingest.  It does not harm the caterpillar, but it will poison almost any predator that  ignores the monarch's bright warning coloration.

Wednesday, August 1, 2012

A full nest

Exactly how many of the Eastern Phoebe (Sayornis phoebe) chicks were still in the nest?  Standing below, I could see two.  They weren't doing much, but I decided to leave the video camera running as I went off to check the rest of the garden.  When I came back after a few minutes, I once again saw two chicks, sitting very still.  Thus, I was in for a big surprise when I watched the footage for the first time.

* 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.

As it turned out, this was the chicks' last day in the nest.  However, the chicks have not gone far: I still hear their "fee-bee" calls from the trees around the garden.