Friday, November 30, 2012

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.

Wednesday, November 28, 2012

Down with the thistles

Canada thistle (Cirsium arvense), an invasive species from Eurasia, is common in this area.  However, so too are its enemies.  Even though the thistles have died down for the winter, I have found several Canada thistle bud weevils (Larinus planus) in the yard.  These weevils seem to be seeking out spots where they can stay sheltered until the spring.

A Canada thistle bud weevil (Larinus planus) sheltering on the lavender bush.
Another of the thistles' enemies has found a very cozy way to spend the winter -- within galls on the thistles' own stems. 

A gall on a Canada thistle stem.
As I was clearing dead plants out of the garden, I came across a couple of dried thistle stems interrupted by these large galls.  I was curious to see what, if anything, was still inside.  Cutting open one of the galls, I found several very odd larvae.

Inside the gall there were several larvae of the Canada thistle stem gall fly (Urophora cardui).
The larvae did not have anything resembling legs or even heads.  They also failed to show any sign of life.  Thus, I initially thought that I must have cut them in half.  However, on closer inspection, I determined that they were all whole.  Although strange to me, this form is normal for Canada thistle stem gall fly (Urophora cardui) larvae at this time of year.  In the fall, the larvae finish growing and suspend their development.  Only in the spring will they pupate and then emerge from the gall as adult flies, ready to parasitize a new generation of thistles.

Monday, November 26, 2012

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

Friday, November 23, 2012

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.

Wednesday, November 21, 2012

Coming in from the cold

When it is cold and rainy, it becomes more difficult to find insects and spiders outside -- but easier to find them inside.  Each day, I discover one or two new "guests" that have arrived in the house.  Although they are all uninvited, I have been letting most of them stay.  Many, such as the spider and ladybug pictured below, are predators that should help to keep the number of other "guests" low.

A spider that was roaming the floor.
A seven-spotted ladybug (Coccinella septempunctata) that has been patrolling my houseplants.
Others are simply too troublesome to handle, such as the several western conifer seed bugs that have gotten inside.  They won't cause any problems as long as they are left alone, but they may release an unpleasant smell if they are disturbed.

A western conifer seed bug (Leptoglossus occidentalis) climbing the blinds.

Monday, November 19, 2012

Saved for a rainy day

It has been cold and rainy for several days, making it difficult to see much of interest in the backyard.  Even when I dared to take my camera outside during a slight break in the weather, my potential subjects were still in hiding.  After some searching, I did find several insects sheltered in various spots around the yard.  The fact that they were not engaged in any interesting activities was somewhat compensated for by their being much more obliging than usual and staying very still as I moved the camera close.

A fly shelters from the rain beneath some flower buds.
Although I did not find much outside, I did discover some unedited videos on my computer.  The video below is from a time when the air was full of insects, rather than water.  I took it to illustrate the surprising number of woolly aphids flying around in early October.  If you look closely at the cotoneaster branches, you can also see the shimmering of spider webs (where many of the aphids ended up). 

* 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, November 16, 2012

The better to see you with

With winter quickly approaching, prey must be getting scare.  Yet, I still find many predators roaming the garden.  In addition to numerous spiders and ladybugs, I recently found one predator that is uniquely endowed to seek out whatever prey remains: a big-eyed bug.

A big-eyed bug (Geocoris sp.) on a hollyhock leaf.
These small bugs use their disproportionately large eyes to locate their prey, which include even smaller insects, insect eggs, and mites.

Wednesday, November 14, 2012

Clones in a row

Pine needles are tough and don't seem like they should be very appetizing.  Nevertheless, after my close encounter with a western conifer seed bug, I decided to start paying more attention to the pine tree in the backyard.  In one of my searches, I found a needle that had been colonized by aphids.

Five aphids on a pine needle.
These aphids can pierce through the pine needle to feed on the sap.  Despite the apparent difficulty of feeding on a needle, they seem to be doing quite well.  When I first found this group of aphids, there were five of them.  When I went back to check three days later, they had already produced three more clonal daughters!

Eight aphids on the pine needle.

Monday, November 12, 2012

In the pink

Leafhoppers are a common sight in the garden, yet I rarely consider writing about them.  One reason is that I never see them do very much.  They feed on plant sap and, consequently, spend most of their time sitting still on plants.

A privet leafhopper (Fieberiella florii) on a rose bush.
The exception is when they are provoked (for example, by my camera getting too close).  Then, they can jump a very impressive distance for an insect called only a "hopper".  However, this interesting ability is difficult to capture with the camera.

A froghopper on a lamb's ear leaf shortly before it escaped the camera.
Another reason to overlook the garden hoppers is their dull coloration.  Until last week, all the hoppers I had found in my garden were some sort of brown, such as the ones pictured above.  Thus, I was very surprised to find a bright pink hopper when I was clearing away fallen leaves.

A pink leafhopper that I uncovered under some leaf litter.
Some leafhoppers are pink as adults, but the one pictured above doesn't match the descriptions I have found.  Another possibility is that it had just gone through its final molt and had not yet darkened to its adult color.

Friday, November 9, 2012

The secret to staying green

While admiring the fall foliage on the crabapple tree, I noticed that some of the leaves still had patches of green, whereas others had turned a uniform yellow.

A crabapple leaf with three green patches.
When I flipped these leaves over, I found a clue to why the patches were staying green.  Wherever there was a green patch on the top of the leaf, there was a matching mine of a tentiform leaf miner on the underside of the leaf.

Three tentiform leaf miner mines on the other side of the crabapple leaf.
Below is a close-up of another mine.  As the leaf miner feeds, it separates the layers of the leaf.  The surface layer then dries and contracts, forming wrinkles on the bottom of the leaf and a tented shape on the top of the leaf.

It seems quite convenient for these leaf miners that the patches they are eating remain nutritious, even as the leaves are senescing everywhere else -- but how does this happen?  Fascinatingly, a study has found that it is bacteria (living within the leaf miners) which are responsible for producing these "green islands" and that they do so by manipulating the plant's own hormone signalling.

Explore some more: Plant green-island phenotype induced by leaf-miners is mediated by bacterial symbionts

Wednesday, November 7, 2012

Ladybugs of a different spot

Most of the ladybugs I've found in the garden recently have had seven spots.  However, ladybugs can vary widely in their number of spots -- from none at all to more than twenty.  Many species are named after their characteristic number of spots, such as the two-spotted ladybug (Adalia bipunctata) pictured below.

A two-spotted ladybug (Adalia bipunctata) on a hollyhock leaf.
Other ladybug species have variable numbers of spots, such as these convergent ladybugs (Hippodamia convergens), which may have thirteen or fewer spots.

Two convergent ladybugs (Hippodamia convergens) on unopened flowers.
Instead of being named after their number of spots, they are named for the white lines that always converge along the edge of the pronotum (the plate immediately behind the head).

A convergent ladybug (Hippodamia convergens) on a hollyhock leaf.
The name 'convergent' is also appropriate given these beetles' tendency to converge into groups of hundreds or thousands to hibernate through the winter.

Monday, November 5, 2012

Two of these things are not like the others

Fruits all over the garden have finally ripened to a vibrant red.  There are crabapples, rowan berries, rosehips, trumpet honeysuckle fruits, and cotoneaster fruits (pictured below) -- all of which add attractive autumn color to the garden.

Berries and autumn foliage of a Cotoneaster sp. shrub.
The bright color of the fruits is not only appealing aesthetically; it also attracts seed dispersers, such as birds, that consume the fleshy fruits but fail to digest the seeds within.  However, not every red thing on the branches is aiming to be eaten.  Spot the exceptions in the photo below!

Two seven-spotted ladybugs (Coccinella septempunctata) among the Cotoneaster sp. berries.
Interestingly, in the case of the ladybugs, the red color serves as a signal that they are distasteful

Friday, November 2, 2012

Painting the garden red

We had a few days of warmer weather this week and, as a result, the ladybugs have come out of hiding.  Almost wherever I go in the garden, I find more of these little red beetles.  Some of them, such as those pictured below, appear to be just sitting around in clusters.

Seven-spotted ladybugs (Coccinella septempunctata) gathered on a hollyhock leaf.
Seven-spotted ladybugs (Coccinella septempunctata) gathered on a rose stem.
Others are going for the last remaining flowers.  Although ladybugs are predators of other insects (particularly aphids), they will consume nectar and pollen when their prey are scarce.

A seven-spotted ladybug (Coccinella septempunctata) on a dandelion (Taraxacum sp.) inflorescence.
A seven-spotted ladybug (Coccinella septempunctata) on an aster inflorescence.