Sunflowers' Headturning

Sunflowers - Wikipedia

A story in yesterday's NY Times describes sunflowers' daily cycle of facing the sun.  This heliotropism (helio-sun, trop-turn toward) is well known in a few other plants as well but these studies tell us more about how and possibly why.

The Cliff Notes version is that young flowers face the sun in its daily east-west arc across the sky, growing larger than flowers in a lab with a fixed "sun."  When those lab flowers are treated with an artificial "sun" which moves, they follow it and grow bigger.  In their natural setting, incredibly, they then reset overnight, facing the east to get an early start on the day.  When they get old, they stop moving (I can relate) and just face the east.

New studies shed more light (sorry!)* on the mechanism.  During the day, the east side of the stems grow, slowly bending the heads west, then overnight the west sides grow, pushing them back facing east, ready for the rising sun.  Meanwhile older flowers facing east all day heat up faster in the morning and attract more pollinators than west facing flowers.  Apply heat to the west facing flowers and more pollinators arrive.

There is much more to the story and I highly recommend reading the NY Times story and the heliotropism link to get a better understanding of this fascinating piece of nature.

*Editor's note: Oh no, he's not.
Thanks to Amy and Steve of the Fishin' Magicians for sending the story.

Skinky Little Eggs

 

Barb was re-potting a yucca on the deck at the creek house when she found these little eggs just under the surface.  They were small and soft like reptile eggs and the pot was too high for a turtle to reach so that left the skinks and fence lizards that race around the deck.

These turned out to be Five-lined Skinks, Eumeces fasciatus.  Mother skinks will hang around to defend their eggs* but we had to move them rather than leaving them exposed to marauding wood rats and squirrels as well as our resident Black Rat Snake.  We decided to adopt them and nestled them into potting soil in a plastic aquarium where they could live on the deck safe from predators.

Lizard eggs are thin and membranous and as such can absorb or lose water.  Soil moisture is important and more moisture tends to produce larger eggs and hatchlings.  A mother skink will cover the eggs with her body in low humidity to keep up moisture content, sometimes even urinating on the eggs.  I didn't go that far but did check the soil moisture and sprinkle it with water.


Thirty days later we found two little skinks crawling around the surface.  Once we released them, we dug into the soil and more blue tail flickered as they dug deeper to escape.  We had a total of 9 skinks out of ten eggs with no evidence of egg fragments or the missing egg. Mother skinks will eat a dead egg but she had no access to the container so its fate will remain a mystery.



Interesting research in Australia showed that at least one species of skink can deliver itself early when it senses a threat.  It was known that signals of predators sometimes prompt early hatching in frog embryos.  As reported in Science Magazine:

"Talk about hatching an escape plan. Unborn lizards can erupt from their eggs days early if vibrations hint at a threat from a hungry predator, new research shows. The premature hatchlings literally "hit the ground running—they hatch and launch into a sprint at the same time," says behavioral ecologist J. Sean Doody, who is now at the University of Tennessee, Knoxville."

Skinks are said to survive in an aquarium with adequate care for 5-10 years.  Ours are free to roam and wave their little blue tails as a thank you until they get over the blues as adults.

* Although the aquarium was moved some distance away next to a wall, we found an adult skink hiding by it several times.  Coincidence, probably as skinks run around the deck regularly, but I like to think it was mom come to visit the eggs.

Addendum:
Lisa Berger asked if other skinks have blue tails.  The answer is yes, all other immature skinks like the Broadhead Skink have blue tails.  Females and juveniles of these two species are hard to tell apart.  The Broadhead's upper lip has 5 scales, the Five-lined only 4.  We have had Five-lined on the deck in the past and I didn't traumatize these wiggling babies by trying to get a closeup side view.

Broadhead Skink- Count the 5 scales on the upper lip.

More information on skinks and the tale of their self-amputating tail is in this previous blog.

Orbweavers in the Woods

Traveling along narrow trails or in the woods this time of year means getting a face full of spider webs.  Watch closely and you will find that they are predominately made by orb weavers, small spiders that specialize in that particular niche between 2-6 feet off the ground.  The webs are rebuilt morning and evening, suspended from a single silk strand between branches of neighboring shrubs.  They are always perpendicular to the ground, perfect for catching small flying insects that are active during those hours. 

Spidermobile

Holding a broken branch in front of you as you walk will sweep most of the webs away but the spiders tend to cling to the stick with a sturdy strand of silk.  I use this technique on my ATV while riding on our trails through the woods.  At the end of a recent ride I had over 30 orb weavers on the sticks, the ATV and me, 25+ Arrowheads and 5 Spiny Orb Weavers. 

The most common species on the trails is the Arrowhead Spider, aka triangular orb weaver, Verrucosa arenata.  Most spider species are hard to identify, requiring close inspection of their eyes, palps, etc.  The female Arrowhead Spider is not only extremely common but quite distinctive with its sharp edged triangular abdomen colored white or yellow, its tip pointing away from the head.  The males have no distinctive characteristics, don't build webs, and are only found on the females' webs during courtship and mating.  As with other spider species, mating is frequently fatal for the male.

The Arrowhead's web is a large circular spiral, one to two feet in diameter.  It is rather loose, billowing like a sail in a slight breeze.  The female spider hangs in the center with her legs tucked in and her head up, unlike the other orb weavers which hang upside down.* 

M. gracilis - Wikimedia

Spiny Orb Weaver - Richard Hover

CD Web - Wikimedia

The Spiny Orb Weaver, Micrathena gracilis, is a common species which also builds its web in the 2-6 foot range above the ground.  It is also called the CD spider as its tightly woven circular web the size of a CD which can look like one when the light is right.

The spider's large spiky abdominal structure is disproportionate to its thorax and is frequently confused for something that it has captured and is carrying away.  Although this growth seems cumbersome and energy wasting, it apparently serves its unknown purpose.  The male has much smaller spines, is usually only seen while mating and often ends up being eaten, giving a whole new meaning to a "dinner date."

Spiny Orb Weaver female - "Does this silk make me look fat?"

In both species only the females build webs; circular structures quite different in size but identically suspended vertically from strong silk lines stretched across trails and openings between woody vegetation.  These are pathways frequented by small flying insects and incidentally, humans.  They specialize in tiny flying insects like mosquitoes, gnats and flies.  After the prey hits their sticky, closely woven silk, the spider bites it, injecting its venom which digests it internally.  The spider then returns later to suck up its predigested juices.

Other side of the branch - Spiny Orb Weaver being sucked dry by the Arrowhead Spider.

I was surprised by the Arrowhead's prey in the picture on top.  After taking the picture, I went to the other side of my spider shield and photographed the prey.  It was only when I enlarged the picture that I could identify as a Spiny Orb Weaver.  Ordinarily it would not be trapped by another spider.  In this case the two species were wildly swinging together from silk threads on a windy ride and once I stopped they came in contact and the Arrowhead won.

* More research on V. arenata's head up position and its effect on speed and web construction is at this Pubmed article. 

 Now photographing their webs has become an obsession.  Stop me before I click again.......

Yellow Mushrooms and Houseplants

Lantana and Leucocoprinus at the Butterfly House - Chris Barnhart

   Wikimedia

The question of the month has been "what are the yellow mushrooms in my plantings?"  It has cropped up twice in the lantana pot in the Butterfly House and is commonly seen in potted plants inside houses.  Meet Leucocoprinus birnbaumii, described in detail at Mushroomexpert.com.

This mushroom has been called a flowerpot parasol, yellow houseplant mushroom and many other names reflecting its presence in gardening and potted plants.  It is native to the tropics and subtropics although the first descriptions were in greenhouses.  It is a saprophyte that lives on decaying plant matter and where does it find comfort in our temperate climate?  How about a greenhouse or a warm sun porch with potting soil and mulch in a pot.

I might argue that in Missouri L. birnbaumii meets my criteria of an invasive species, albeit a rather benign one.

• It is exotic, that is nonnative to the ecosystem under consideration, i.e. the temperate midwest.
• It is spread by humans to those regions, in this case in potted plants.
• Causes environmental or economic damage or a danger to health.  While mild, the number of gardening sites answering questions on removing or preventing it suggests some folks are spending time and effort fighting it.

Later, parasol now open - Wikimedia

Some have suggested that it could be poisonous.  This is one more opportunity to tell your children to never eat a mushroom unless it is identified by an expert.  Don't let your pet eat it.  I have never seen any of our dogs eat a mushroom (although Duke eats everything else he finds outdoors.)

I would argue that it should be considered a bonus, an unexpected if somewhat temporary colorful gift from the soil.  Some resources have even proposed that florists should consider selling mushrooms in pots, or at least throw in a few L. birnbaumii spores with each purchase.

Sumac Gall Wasp

Wasp in a sumac gall - REK

  James Trager

Continued:
That evening when I cut into the largest smooth sumac gall there was a small 5mm black insect laying among the living aphid larvae.  The gall had been intact with no visible entry point.  I photographed it with the microscope and sent it off to Chris Barnhart for an explanation.

"Appears to be a gall wasp, Torymidae (Superfamily Chalcidoidea, the Chalcid wasps).  I think that it developed in there (grew from an egg laid in the gall by the parent) and you opened the gall just before it would have emerged. They have to chew their way out. Yours grew up as a larva eating aphids, I suppose." CB

Since then this ID was confirmed by Bugguide.  Key features of this Torymidae family are their metallic bodies and the large hind legs.  They are small, from 1.1mm to 7.5mm, (less than 1/3") and have a long ovipositor, sometimes longer than their body.

1.1-7.5mm in length

1.1-7.5mm in length

They are commonly parasitoids of gall forming insects although some species are plant eaters and just take over the gall for housing.  Many use their ovipositor to inject their egg into a gall.  There is a wide variety of behaviors depending on the species.  Parasitoids are parasites that eventually sterilize, kill or even consume their victims.  Other Torymidae are inquilines that develop inside the gall, living in the gall space and likely eventually killing the original inhabitant. 

The study of parasitoid wasps is quite complex and I haven't scratched the surface.  I was unable to find any information on the genera or species of wasp associated with the sumac leaf gall aphid, Melaphis rhois and my photographs are not sufficient to narrow down the choices.  I am left with the wonder of this microcosm, a wasp that grows up in an aphid's gall while the sumac continues a healthy life.

More detailed information on the Torymidae family is at this link.
The parasitic way of life has evolved many times as described in National Geographic.

inquilines Inquilines

idiobiont ectoparasitoids

Sumac Gall

Smooth sumac with galls - REK

  James Trager

I found a smooth sumac (Rhus glabra) at the Watershed Center that had a number of yellow galls on the underside of its leaves.  These galls are produced by aphids but that is only the beginning of a fascinating story.  I cut into a number of galls to see the early stages of development, a view better seen in James Trager's photograph.

The process begins in the summer when a winged parasitic sumac leaf gall aphid, Melaphis rhois lays a single egg on the underside of a sumac leaf.  The egg induces the leaf to produce a protective covering where the offspring can live fed by the plant and protected from predators.  The single egg reproduces a series of generations by parthenogenesis (reproduction from an ovum without fertilization) so that an individual gall may eventually hold 3-4 generations of larvae.  I opened 6 galls and estimated that there were between 200-300 aphids per gall.  You can see the different instars in the photograph as well as in this video.

M. rhois larva - Claude Pilon

Cut gall - 4 instars of larvae - REK

 Winged female aphids - Larry Clarfeld

 Winged aphid - Claude Pilon

In late summer winged females will emerge from the gall and fly off to moss to establish asexually reproducing colonies.  These offspring are male and female and their mating will produce the eggs that will be back on sumac next spring.  This life cycle requiring two plant species is unusual but not unique.  In 1989, it was reported that the use of alternate plant hosts by the aphids dates from 48 million years before present.  This Melaphidine aphid life cycle can be dated back 48 million years when the Bering land bridge supported both the aphids and their two plant lifestyle on what was soon to be two separate continents.  See ncbi.nlm.nih.gov.  When identified, this was the oldest known documented insect-plant relationship."  Wikipedia

Complicated?  Just wait for the next blog when we will discuss this insect that I found in the first sumac gall I cut into.

An overview of gall-making insects is at this link.

Fall Webworms of Summer

When I saw the first webs the first webworms in little clusters in June I didn't think it could be "Fall Webworms", Hyphantria cunea.  I was used to the large webs covering a whole branch and these were just on a couple of leaves.  I was wrong, they were just warming up.



The web was full of caterpillars and their frass which is exactly what you think it is.  The cats were moving about very slowly even though the brisk breeze was whipping the branch around.  I grabbed the branch and they immediately sensed the difference and began to crawl around frantically (for a caterpillar), showing evasive behaviors as seen in this real time video.

"One generation per year emerges in the northern part of North America, with larvae appearing in late summer through early fall. South of an approximate latitude of 40°N there are two or more generations annually, with webs appearing progressively earlier further south."  Wikipedia

OK, so what are they doing here so early?  I suspect there are two factors.  We had a record population last fall, prompting lots of newspaper and TV reports.  This means there is a larger graduating class of adults in the spring.

As temperatures rise some moths may emerge earlier and lay their eggs ahead of schedule.  Successful reproduction requires that a food source be available when caterpillars emerge from the eggs. Studies show that the first leaf out time is occurring earlier in recent years, so there is now food for the young caterpillars available earlier.

Second instar - REK

H. cunea overwinter as a pupa (that is in cocoons), and the moth emerges to lay eggs the next year.  In Missouri that has been in late summer but with Global Warming (yes, I actually said it), they likely are emerging earlier leading to the two generation latitude moving north from 40° to our 37° N.  Contrary to Wikipedia, in southern Florida they may have 4 generations a year!

Moth - Wikipedia

The moth is small but kind of cute with a bushy head of fuzz.  The wings are white in the northern range with black speckled fore wings in the south.  It will be interesting to see if there is a change in wing coloration with time if multiple generations occur in Missouri.

Cocoon - Andrei Sourakov

Pupae - Andrei Sourakov

H. cunea is a "reverse invasive species," introduced into Yugoslavia in the 1940s it is now over all of continental Europe as well as in China and Japan.  A cynic might say this is a fair trade for Japanese Honeysuckle and Garlic Mustard but as usual we brought it on ourselves.

Fourth instar - Shelly Cox

One element of their success is their wide range of food plants.  They have been reported to eat at least 636 species of leaves.  Fortunately they haven't developed a taste for animals or we might all be in trouble.