Nature Blog Network

Wednesday, October 1, 2014

Long-jawed Orb Weavers








 

We were sitting on a pond dock when someone spotted this creature stretched flat along a pole above the water.  Its slender length was dramatic enough that at first glance we weren't sure what kind of insect it was, but after counting its 8 legs we clinched the diagnosis as a spider. 

Its posture and the jaws extending way in front of its head is a dead giveaway to its identification.  This is a Long-jawed Orb Weaver (LJO) of the family Tetragnatha (four jaws in Greek).  There are over 1,000 species found world wide, especially in the tropics, but only around 15 species in the US.  Identification of the species requires a specialist with lots of magnification to see parts that you and I could not identify. 

Also called "stretch spiders", LGOs extend their legs when threatened to hide on a blade of grass.  With their long legs and light weight body they are able to run on the surface of the water like a water strider. The third pair of legs which are much shorter are used to cling to grass or other vegetation as they stretch their other longer legs out in front and behind, blending in to the leaf blade. 

Spread legs in a box
Even with a pocket camera you can still get decent pictures.  Using only a Panasonic Lumix camera with no specialized equipment you have to get your subject's permission to get up close.  I use a plastic box or container such as a margarine bin with smooth sides to keep the subject from climbing out.  If it is too active, a brief stay in the refrigerator will slow down the action.  You can see it has long jaws extending forward as well as the short third pair of legs.

"My what big jaws you have!"- note right fang.


Although named orbweaver, they are in a different family from the classical Araneidae orbweavers such as the Argiopes we discussed recently.  The Tetragnatha create their orb webs parallel with the surface of the water to pick up prey flying along the surface.  Their typical meal includes species like mayflies that emerge from their aquatic larval form into flying insects or insects that develop in the muddy banks like crane flies.

Front view - Note eyes, chelicerae with folded fangs
Once slowed down, I was able to move it into a different box to get the camera close for macro photographs. The eyes are now visible as raised black spots on the head.  The chelicerae (jaws) look blunt and club shaped, but you can see the fangs folded up along the inner edge.  Like a venomous snake, the Tetragnatha can control the amount of venom they inject.

Lip-locked mating - Youtube
Many female spiders are known to eat their potential suitors or even the male  after after they have mated.   The LJO has an interesting defense against this reproductive hazard.  They grab each others chelericia and holding on tight while the male delivers his vital fluids by using his pedipalps.  This gives a whole new meaning to the term "lip-lock".  You can see a video here but don't expect a lot of action.

More on LJW species at this website.

Sunday, September 28, 2014

Beautiful Fungi

Beautiful..... and a slime mold - Trichia decipiens
Fungus and beautiful are two words you may not think belong in the same sentence, but Mark Bower's photography may change your mind.  His updated exhibition of the mushrooms of our area will be on display through the month of October at Burr Oak Nature Center in Kansas City.


Pseudomerulius aureus - Click to enlarge
For those of you who saw his exhibit at the Springfield Conservation Nature Center this year, there is still more to see.  He has added a number of species including some that I think are his best works ever.

Stemontitis sp. (Chocolate Tube Slime) - Click to enlarge
Many of these are tiny slim molds.  The whole set are on line at this Flickr link.  Simply click on the picture and then thumb through them.  At the bottom you can get more information on the species by clicking on "for more information".

Mycena caerulea - Click to enlarge
His other Flickr albums are here.
Mark is a member of the Springfield Plateau Chapter of Missouri Master Naturalists and the Missouri Mycological Society.

Thursday, September 25, 2014

Ladies'-tresses Orchids

Photo by Mark Bower
We recently had the pleasure of botanizing at Bull Mills with Doug Ladd of the Nature Conservancy.  While we were standing in the cemetery and I rambled on about the history, Doug turned around and pointed out a few tiny orchids standing above the mowed grass, something that none of us had noticed.  These were slender ladies'-tresses orchids Spiranthes lacera, a genus he had discussed at our Master Naturalist meeting in June.


Identifying orchid species can be intimidating but ladies'-tresses are distinctive.   The genus Spiranthes comes from the Greek speira, meaning "coil". Their inflorescence (cluster of flowers) is arranged in a spiral down the stem.  I was able to identify it as S. lacera because of the distinctive green or yellowish-green spot on the center of the labellum (lower modified petal).*

Photo by Mark Bower
The details of the tiny petals were impossible for me to capture with my equipment so I called Mark Bower.  He came down the next morning and took these beautiful pictures which show the orchid's distinctive features.  You can easily see the "yellowish-green spot on the center of the labellum" that was hard to see at ground level with a magnifier.

S, lacera range- Wikipedia
Orchids, like bobcats and black bears, are what I think of as common yet uncommon Ozark species.  If you look at a range map, orchids occur over the Eastern US and Canada and yet we haven't seen them before and native plant enthusiasts will make field trips just looking for them.  Their brief period of flowering and diminutive size lead to their infrequent discovery.  Even on the mowed grass we had a hard time finding all of them.  However once you've seen one you are much more likely to recognize another.  On subsequent days Barb found them while eliminating some sericea lespedeza between  trees bordering a bottom land field and under a power line cut.

Photo by Mark Bower
Gobotany.newenglandwild.org has details.


What is it?
Below is a photograph I was sent by our friend Georgia, who found it on the edge of her dog's water bowl.  She asked me what it was and I was way off with my first guess.  Now you can try before we answer it in a posting next week.
Animal, vegetable or mineral?

Monday, September 22, 2014

Pawpaw Poacher

Asimina webworm
Click to enlarge
While I was checking out a pawpaw (Asimina triloba)  grove for fruit, I noticed that most of the trees had some of the leaves hanging down, pale to dry and shriveled.  The damage seem to occur along the petiole and they were usually stuck to an adjoining green leaf with silk.  This was my introduction to a pyralid moth, the asimina webworm moth, Omphalocera munroei.

Wrapped in silk, heading back into the frass
When I began to carefully unwrap these leaves I found occasional caterpillars, small and brightly colored.  They were deep inside the leaves which were bound together by silk and filled with frass (insect poop).  As soon as I exposed one, it quickly crawled further into its protective frass-filled pouch.  When I put one on the hood of the truck it thrashed violently and crawled to escape much faster than the average caterpillar.

Adult asimina moth -  Mark Dreiling
The tiny moth lays it eggs on the underside of older pawpaw leaves.  Although studies have shown that their caterpillars grow better on fresh young leaves, the older tougher leaves make a better protective shelter.  The earliest larvae pull leaves together with their silk to create a communal home while later instars will live singly in rolled leaf edges.  Both types of shelters have been shown to help protect them from predatory wasps which lay their eggs on caterpillars for parasitic development of their young.

Green and dead leaves form the shelter
A caterpillar will chew on the petiole, causing the leaf to die and dry out.  It will then tie it onto a fresh leaf with silk, the dry leaf providing protection while it chews on the green one.  Soon there may be four dead leaves forming its cave before it heads out to another branch.  Eventually the moth can even defoliate the tree late in the season as well as bore into the fruit.

Chewed leaves and new leaf growth
While this is not good for the individual pawpaw tree, it may benefit the zebra swallowtail whose caterpillars require pawpaw to grow to adulthood.  The zebra cats also grow best eating younger leaves.  After the asimina caterpillars kill leaves, the pawpaw responds by growing new fresh leaves that the zebra cats need.  Meanwhile, the asimina stick to their mature leaf diet for their shelter properties.  In Florida this has been shown to increase the number of second summer broods of zebra swallowtails
.
Our asimina babies

Editor's note
We are currently raising Asimina caterpillars out of curiosity, just to see the adult moths.  Who knows why, as there are more than enough of them this year at Bull Mills.

  • Details on the zebra swallowtail-pawpaw connection are in this blog.
  • Pawpaw is also host to the pawpaw sphinx moth, pink-spotted hawk moth, and tulip tree beauty moth.

Friday, September 19, 2014

Scelionidae Wasp Hatching


Mark Bower sent me these pictures last month, a good example of what you can find with curiosity.....and a good photographer.  These eggs are 1mm in diameter (1/25 of an inch), hard to see with a magnifier and impossible to photograph.  I asked him to describe his find.
"These eggs were deposited on a wooden post on our front porch. When the first one emerged, it stayed with the eggs constantly. When others hatched, the first one watched intently, and immediately either attacked or mated with them. I say two "hatchlings" get attacked and expelled from the egg cluster, one gets mated with, and several others die (why?) before they could get out (after opening their eggs). Not sure what all was going on there; it all seemed sort of odd."
We sent this to Chris Barnhart who explained that "these are parasitoid wasps, emerging from eggs of hemiptera. The wasp is likely in the Scelionidae family."  Hemiptera are the order of "true bugs", the order that contains aphids, planthoppers, leafhoppers, shield bugs, and stink bugs that often plague your garden.  In this closeup Youtube video by Mark, at 1:03 you can see a wasp emerging from a hemipteran egg and an immediate attempted mating by a newly emerged male who was waiting for her to come out.

Not all species are black
The scelionidae family contains over 3000 species of parasitoid wasps.  They all lay their eggs on the eggs of insects or spiders where their young grow by using their host  as food.  Generally they are careful to eat only nonessential parts at first, prolonging the life of the host to obtain maximal nutrition.

These wasps and the eggs they attack are tiny!
Antennae with 9 visible segments
A typical scelionid wasp is black and slender although some are various colors and shapes.  In general they have long elbowed antennae with 9 or 10 segments.  These are tiny creatures, ant sized, and could be mistaken for them without magnification.  Most are winged except for some species that parasitize wingless beetles.

A miniscule wasp measuring 3mm in length would have a difficult time fly all over looking for insect eggs to parasitize but they have developed a strategy to find a host for their young- hitchhiking.  They get on the back of a female insect and hang on until she starts laying her eggs.  Then the wasp gets off and starts laying her eggs inside her hosts fresh laid eggs.  Finally, she adds a strong odor, warning away any other parasitic wasp that these are taken.*

Winged scelionid wasp
We tend to be judgmental about plants and animals, classifying them as "good" or  "bad" by our personal criteria.  In ecological terms, many "bad" bugs and plants are just misplaced, located where it is inconvenient or problematic for us.   Eating our garden or the caterpillars of butterflies we treasure labels them "bad".   Meanwhile they are, to paraphrase Arthur Dent in Hitchhikers Guide to the Galaxy, "just these bugs, you know", making babies the best they can.  And if you look closely, they can even be a little cute.
Cute? -  Compound eyes, "The better to see many of you with."
 *  More details at this beesnwasps.com page.

Thursday, September 18, 2014

Monarch Migration

Monarch emerged, dry and ready to take off
Chrysalis before emerging
As we watch the last of our monarch butterflies from Linda Bower emerge from their chrysalids to head south to Mexico, we are reminded of the challenges facing them.  First there is the emergence from the dried skin of the chrysalis itself.  They must hang on while pumping blood down into the veins of their deflated wings, expanding them with the help of gravity until they dry.  Falling or failure to hang properly can lead to deformity that sentences them to a brief stationary existence.

Failed wing expansion
Once their wings have dried and we release them from the rearing cage, they have to warm up their flight muscles, not easy on these last few cool, overcast rainy days.  Under these conditions they take off later and land earlier, frequently dependent upon the sun.   An observer from Ontario a few days ago reported, "We conservatively counted 1,000 monarchs from 11 a.m. to 2 p.m., at 4 - 8 per minute. Then the sun went behind clouds and all stopped!"*

Migration progress 9/17/2014 - Learner.org
You can follow the progress of migration thanks to citizen science reports on
Learner.org  including some day to day personal observations from Canada and the northern states as the migration begins.  The Learner.org maps show the day to day progress of the wave of monarchs heading to their winter quarters in Mexico.  Other maps show the location of adult butterflies, eggs and larvae, and fall roosts.

The migration of species has always been of interest to nature lovers, but now with the tools of the Internet, we have the ability to follow their journey.  Citizen scientists all over the US reporting their sightings of monarch butterflies and hummingbirds allows us to see the big picture as well as understand changing patterns of migration brought on by human activity and climate change.  Someday there may be tiny chips that allow us to follow the monarchs we raise.  Waaay too much information!

Friday, September 12, 2014

Hummingbird Predator


Not much eats a hummingbird between their speed and their aversion to sitting still.  Still every creature and plant has a place in the food web, including humans.  In the case below it was truly a food "web".

I was hiking along Bull Creek and noticed a few cardinal flowers down stream, a brilliant flash of bright red on a cloudy evening at sunset.  I went down to photograph them, and while trying to focus in the low light I saw something move off to the side.  It was a large yellow spider busily wrapping up its prey, suspended from a single silk "baseline" stretched between two branches of bushes.  It had the coloration of the common yellow garden spider,  Argiope aurantia,  discussed in a previous blog but was not quite a match.  This one was the banded Argiope, Argiope trifasciata.

As I was taking pictures, I suddenly focused on a long slender beak protruding from the silk wrapping.  On the other side I could just make out the iridescent green of a hummingbird's wing under the silk cloak.  There was no ruby throat so it must have been a female or juvenile. The web had been suspended in front of the cardinal flowers which just happened to appeal to a ruby-throated hummingbird.  It is possible however that the hummingbird wasn't an entirely innocent victim.
"Hummingbirds use spider webs as a source of spider's silk in nest construction, being necessary to bind the nest to the tree branch or other substrate and to hold the nest together. Even so, the hummingbird must be careful when removing the pieces of webbing, for it may become entangled and be trapped there. Spider's silk has a tensile strength comparable to steel on a weight basis. In one report, a ruby-throated hummingbird was caught in an active web, and quickly wrapped and encased by the spider, much as an insect might be." Hummingbirdsociety.org
Spider web construction varies with the species and many spiders don't even bother to make one.  The initial strand in web construction of Argiopes' is called the "baseline."  It then drops a single line in a "Y" and builds the radials before adding the sticky web.  Most lose stickiness after a day and are eaten by the spider who then, in the ultimate in recycling, uses the ingested silk to reconstruct the web.  Details and diagrams of their techniques are at spiderzrule.com.


When most prey hits the web, the spider rushes out and bites it, killing it before its thrashing allows it to escape.  With some venomous insects like wasps they just carefully wrap it in silk. Once our Argiope realized I was intruding it slowly made its way along the single strand of baseline to the anchoring branch.  The baseline is incredibly strong and it was stretched a foot as I pulled the mummified humming bird off the strand, before the baseline snapped back in place without damage.

Most things in nature have a purpose, even if we can't guess what that is.  A recent study on the Web Orientation of the Banded Garden Spider, Argiope Trifaciata found that they oriented their webs in an east-west direction, and then suspended their ventral (underside) surface to the south, picking up the maximum sun rays.  This surface is dark on A. trifaciata, which increases its heat absorption.
"The spiders grow throughout the summer, reaching full-size in late August and September. The males, which are much smaller than the females and do not produce webs, roam around the vegetation and mate the females in late summer. The female then lays one or more egg sacks, that appear somewhat like a small kettle drum with a tough papery cover and may contain 1000 eggs apiece. The spiders die after frost and there is only one generation produced each year."  Colostate.edu
 Stabilimentum-Wikimedia
Argiopes seem to be proud of their webs, creating a beautiful radial pattern and some species even construct a "stabilimentum" decoration along the vertical axis of the web.  There are many theories about the purpose of this structure which are discussed at this site.  Even before "some pig" appeared in Charlotte's Web, folk tales said that if you saw your name in the web, you were about to die.   I don't know how to spell "hummingbird" in bird-speak, but it may be a zig-zag.


And yes, the hummingbird had gone to that big sugar water feeder in the sky.