Sunday, October 13, 2019

Twig Girdlers

Twig girdler, Oncideres cingulata - Dave Rintoul
This is the time of year our forest floor becomes littered with small tree branches with a distinctive break at the end.  They look like they have gone through a blunt pencil sharpener, ending in a jagged tip.  This is the work of twig girdler beetles, Oncideres cingulata.  These are long-horned beetles of the Cerambycidae family.  



In the summer after mating, the female straddles a small branch and chews a V-shaped groove in the outer portion around the twig, leaving the center portion intact.  Her feet grip the tender bark, leaving a series of horizontal grooves in the distal branch.

Hole for egg - Chris Barnhart (CB)
Next she chews a small hole in the bark of the outer half of the branch and deposits an egg under the bark.  
The eggs are long and narrow, fitting into a tiny hole usually at the site of a side branch.
Egg in its chamber - CB  Click to enlarge

The number of eggs per twig normally ranges from 3 to 8 but may range up to 40. Adults live 6 to 10 weeks. 

Each female deposits 50 to 200 eggs which hatch in about 3 weeks.   OKstate.edu

Larva writhing around in its frass chamber - (CB)
This will be her offspring's home until next summer, slowly enlarging its chamber while living in its woody poop (frass for insect connoisseurs).  Her larvae require dead wood to develop and the cut effectively cuts off the twig's circulation.  They cannot fully develop in green twigs with high moisture content. 

The legless grub will live in the twig all winter whether it falls to the ground or occasionally dangles from the tree. The chamber hollows to provide a winter home as the grub rests.  It starts feeding again in the spring and grows up to an inch long, living in a world of its frass which provides some insulation.  Eventually it chews an exit hole for the future, then pupates in the frass before emerging as an adult beetle in late summer.

You can see some of the action in Dr. Chris Barnhart's video here.  Meanwhile a couple of beautiful final portraits from Chris of the emerged adult, Oncideres cingulata.  
Note: 2013 blog updated with video.


Sunday, September 29, 2019

Wolf Spider Hole

A front hall made from dried grass and silk - REK
Another view
On our MN training field trip to Henning CA we came across several of these mystery features in the barren ground between grass clumps.  They were approximately 6-8mm in diameter (1/4 inch) and extended 8mm above the ground.  They were constructed from bits of dried grass.  I sent it to Chris Barnhart while we were in the field and he suggested a wolf spider hole.





Burrowing wolf spiders are in the genera Geolycosa (geo=earth, lycosa=underground).  Most of these are found in Florida but one species, appropriately enough named Geolycosa missouriensis, is found all the way into Canada.  Based on circumstantial evidence alone, I am calling this its home until someone comes up with a better suggestion.



Kurt Schaefer
Geolycosa missouriensis is a common species of spider within the wolf spider family, Lycosidae.  These are all ground dwellers, efficient predators with good eyesight that hunt with speed and strength to capture prey items.  They don't build webs and reserve their silk for lining their tunnels and collecting debris to form a little raised opening.

This Bluejay Barrens blog has good photographs of the spider in its burrow.  Looking closely you can see the diagnostic eye arrangement of a Lycosidae. 

As usual, insect guru Bug Eric has a lot more detailed information.  Finally, here is a video of an unidentified wolf spider goaded out of its home.

Friday, September 20, 2019

Yellow Garden Spider Revisited

I took one look at you ....and my heart stood still--------Rogers & Hart
stabilimentum
On a field trip with the future teachers of Discover Nature Schools we ran into this beauty.  The distinctive zigzag pattern seen vertically through the web is called a stabilimentum. It is common among the Argiope sp. (Ar-gee-O-pee) spiders but is produced by over 80 spider species.  A. aurantia makes an especially thick stabilimentum. It is called a "writing spider" from an old old folk tale that says if you see your name written on its web you are about to die.  So much for the kind and empathetic writing of Charlotte's WebNo students were lost on this trip.

This is a female Argiope aurantia, the yellow garden spider.  The females are three times larger than the males with a body length of 19-28 mm.  The Araneidae family members all have eight eyes in a distinctive arrangement but with black eyes on a black face they are hard to photograph.  This is a very active spider that crawls all over our hands.  I was finally able to get head shots by gently holding it between soft foam rubber pads.  Her pedipalps are long and narrow compared to a male's which are specialized for the job of transferring sperm.

Male and female - Jay Barnes
The beautiful circular web A. aurantia builds is temporary, as they eat all but the long foundation webbing every night, spinning a new web for the next day. Some sources suggest they may do this to add tiny particles to the webbing which look like food to small insects, drawing them to the web.

The zigzag stabilimentum is especially interesting. It is made of a slightly different webbing which reflects UV light, possibly attracting insects to it. It is important to recall that other species frequently see different light waves. Other biologists believe the stabilimentum is made to strengthen the web, confuse predators, or to warn birds not to fly into the web.


A stabilimentum didn't save this hummingbird that flew into a web in front of one of our cardinal flowers, Lobelia cardinalis.  The closely related Argiope trifasciata spider went into its reflex action of wrapping up its prey (or bycatch in this case).  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.

Whether you like Latin names or not, the name Argiope aurantia is necessary to confidently identify the species.  Using "binomial nomenclature" creates a universal name recognized in all languages. Between three different authoritative sources it carries the common names of writing spider, corn spider, black and yellow garden spider, zipper spider, banana spider, x spider, corn spider, the yellow and black garden spider, the black and yellow argiope, the golden orb weaver, and yellow argiope.  This impressive list demonstrates the importance of a scientific Latin name.


The story of a female spider eating the male after mating is a familiar one in many species (see black widow blog). The Argiope is different.  The male effectively commits suicide by sex. Spiders transfer their sperm to females using their specialized palps which the male inserts into the female.  In the case Argiopes, they die right after inserting their second palp, their heart stops beating several minutes later.  This gives a whole new meaning to Rogers and Hart's lyric, "...and my heart stood still."

The second palp remains inserted into the female, effectively plugging the opening and preserving the male's genes from contamination from another male. In other words, he makes the ultimate sacrifice to preserve his inheritance.*
The male’s death is also described as an “irreversible seizure” and apparently this takes place to form a kind of “chastity belt” (James 2003*). Once the male Kamikaze has inserted the second palp, he’s stuck, despite what the surrounding males would like. "The other males go berserk, bite into the legs and try to pull him off." Securing himself inside of her also gives the male’s sperm sufficient time to fertilize the eggs.**
Meanwhile the female never gets to enjoy her 1000+ kids.  She makes a round brown egg sac, attaches it to the web and watches over it.  The spiderlings hatch but the newborn spiderlings remain in the sac over winter while she dies.  They will emerge in the spring to spread out into new territory.  I wonder if the thought of raising 1000 kids is what kills her?

"Bug Eric" Eaton's blog
*    See this NIH publication.
**  Comprehensive A. aurantia information with references is at this link.

More photographs in Bugguide.

Tuesday, September 17, 2019

Life on a Spicebush

Life on a spicebush leaf -Tonya Smith
I borrowed these photographs from Tonya Smith MN who has recently become addicted to macro photography.  Recovery is seldom possible so I am using this blog as a warning to others who might be spared.  She found this on a spicebush leaf and sent it in to Bugguide on September 5th as a Bug Track.  On the 10th, she had this reply.
"This is a row of eggs inserted under the leaf epidermis. The little lid-like appendage at the top of each one suggests Heteroptera, and my first guess is Miridae (plant bugs), but I don't have any experience with their eggs, so it would be great if you could collect the leaf and see what pops out. Great photos!"… Charley Eiseman, 10 September, 2019 - 5:49am
Closeup with "lid-like appendage on top" - Tonya Smith
There are several lessons to be learned here.  First, there is a community of fellow "macrophiles" out there who are willing to give a helping hand, although some like me can be wrong at times.  Charley Eiseman, quoted above, is the guru and has helped me out several times and is generous with his expertise.  After years of assisting me in my gall addiction, he has ventured into life "in a leaf."

Leaf miner on Verbesina virginica - REK
While chasing chasing tiny critters on leaves I frequently see these scars.  They may occur on the upper or lower surface, sometimes on both.  I had always assumed that they were caused by something browsing the epithelium but it turns out to be something much more interesting. 
A leaf miner is any one of numerous species of insects in which the larval stage lives in, and eats, the leaf tissue of plants. The vast majority of leaf-mining insects are moths (Lepidoptera), sawflies (Symphyta, close relatives of wasps), and flies (Diptera), though some beetles also exhibit this behavior.  Wikipedia
Leaf miner tunnels with trails of frass - REK
Note that it says "lives in."  These tiny larvae mine in between the upper and lower surface epithelium, frequently leaving little tiny strings of dark frass (insect poop).  Eventually they emerge, leaving through a small exit hole which you may see under magnification.

If you want to pursue leaf miners beyond the Wikipedia reference, Charley has just published  Leafminers of North America.  It is 1857 pages long (plus a 54-page table of contents, 20-page glossary, and 68-page bibliography), illustrated with thousands of color photographs.  To prevent injury to the UPS delivery drivers it is only available as an ebook but it is a great reference.  "Abandon all hope, ye who enter there" for I have sampled the incredible deep dive into my copy and it is hard to emerge.

=====================
He and Noah Charney wrote Tracks & Sign of Insects and Other Invertebrates which is an indispensable book for those who wander through nature wondering "what made that?" be it a gall, egg case, pupae, exuviae or an engraving left by an insect. 

Sunday, September 15, 2019

Little Stinkpot


Saturday's field school for the Master Naturalist training class turned up a cool cold-blooded specimen in the creek, an eastern musk turtle, Sternotherus odoratus, the smallest Missouri turtle and one of the smallest on the planetOdoratus is Latin for "fragrant" and its alternate common name of stinkpot sounds ominous.  This is because of scent glands from the edge of its shell which can release a foul musky odor. possibly to deter predation.  Realizing that these were naturalists, it held its fire (or maybe he was just too young for his hormones to arrive.)

"Just call me spike."
Working with the WOLF School, the students almost always give a name to a turtle, snake or even a worm.  I tend to refer to specimens I pick up as "he," a trait that frequently gets me in trouble with my wife.  In this case I am justified as Wikipedia says that "males can usually be distinguished from females by their significantly longer tails and by the spike that protrudes at the end of the tail.

This is a very wise looking turtle, somewhat anthropomorphic but said with affection.  The MDC Discover Nature Field Guide described it this way.  "There are normally two thin, yellow stripes on each side of the head and neck. Small projections of the skin called barbels are present on the chin and throat."  To me it looks like it missed a few spots on its chin while shaving.  Technical note: even male turtles do not shave.


The MDC Field Guide describes its diet writing "A variety of small aquatic animals are eaten by this small reptile, including aquatic insects, earthworms, crayfish, fish eggs, minnows, tadpoles, algae, and dead animals."
"This species is most abundant in slow-current sections of rivers and larger streams of the Ozarks, the swamps, sloughs, and small ditches of the Bootheel, and in a few rivers in the northeastern part of the state. They can also be found in reservoirs. It favors shallow water but also basks on logs, rocks, or small, horizontal tree trunks"
You can't buy Master Naturalist fun like this!  Photos by Becky Swearingen.
For more details go to this Virginiaherpetologicalsociety.com link.

Wednesday, September 11, 2019

Velvet Ant Revisited

Some years ago I was out with some young naturalists.  All kids are naturalists if given a little freedom and encouragement.  They found this critter running rapidly through the cropped grass and weeds by our swimming hole.  The consensus among my young colleagues was "Wow, look at that ant!" and they were partially correct.  It is a velvet ant, an "ant that ain't," actually a solitary wasp of the family Mutillidae.

I chased this swift creature for several minutes before I was able to get it into a bug box.  Due to its formidable appearance, I was never tempted to touch it during the chase, a wise decision.

Male velvet ant - C. S. Lewallen - Entnemdept.ufl.edu
Velvet ants are characterized by their dense hair in vivid shades of red, orange or yellow.  The males have wings and usually have different coloration from the wingless females.  Bright colors in insects are frequently warnings of toxicity or the ability to hurt predators like us.  Other harmless insects may also have these colors, a form of mimicry.

Their other name is "cow-killer" which probably gives you a hint of their defense. The name derives from the female's stinger.  Although one species of velvet ant has a sting rated as a three on a one to four scale, many species' venom strength is less than a honey bee.  The Schmidt sting pain index was created over the years by entomologist, Justin Schmidt, prompting insects to sting him and then grading them on the severity of the pain in terms usually reserved for a wine connoisseur

Adults feed on nectar and water.  The male flies looking for females on the ground. They are parasitoids, rearing their young which slow feed on other species, eventually killing them.  Finally they emerge, the male flying off and the female crawling away as a warm and fuzzy "ant" - well maybe not so warm.
"Male mutillids fly in search of females; after mating, the female enters a host insect nest, typically a ground-nesting bee or wasp burrow, and deposits one egg near each larva or pupa. The mutillid larvae then develop as idiobiont ectoparasitoids, eventually killing their immobile larval/pupal hosts within a week or two." Wikipedia
Ant Petiole - UCIPM
One way wasps differ from ants is by their thicker pedicel ("wasp waist"), the connection between abdomen and thorax.  Ants have one or two petiole nodes between thorax and abdomen.  For identification of a velvet ant, just go by the color, don't bother picking it up to see this detail.

Monday, September 9, 2019

Pawpaw for WOLF




This week we had a record harvest of fruit on the pawpaw trees growing along the trails.  We ended up with 17 pounds, 4 times our average year.  Many of the biggest ones were hanging in clusters.  We go after them with a long pole with a hook on the end, pulling down all we see.  We have learned that when you think you have reached all of them on the tree, give it a good shaking and more unseen fruit is likely to come raining down on your head.

Pawpaws have a tight green skin, firm until they ripen, then soft, squishy and  full of the sweet odor of a over ripe banana.  Inside, there is a pale custard-like pulp with several brown seeds.  Fortunately those characteristics make some people dislike them which means more for us.  The pulp makes wonderful pawpaw pudding, the consistency of a moist cake.  It also can be used for pawpaw bread or served on top of ice cream.

The pawpaw tree (Asimina triloba) is much more important for wildlife.  Their fruits are popular with squirrels, raccoons, and bears.  In season we see bear scat filled with seeds, the pawpaw tree's method of transporting its offspring out of the neighborhood. 

Pawpaw flowers, fresh, dead and frost damaged - REK
Bud ready to flower
Pawpaws bloom early in spring and sudden freezes turn them into shriveled dark brown blobs, robbing them of the chance to make fruit.  Their survival trick is to spread out their flower bloom times.  We have noticed over the years that the flower blossoms develop and open up sequentially over 4-6 weeks in the spring.  On the same branch there may be shriveled frozen buds, tight buds both ready to open and fully opened blossoms, the whole spectrum on a single tree. 

Pawpaw also reproduce by suckers, roots extending out to establish trees nearby in an expanding community.  Left alone they could cover a large area but as a forest matures over years around them, their expansion is controlled.

Pawpaw flowers in full bloom - REK
Like other species producing dark brown to purple flowers, the pawpaw flower smells bad, somewhat like rotting flesh.  This attracts insects that normally seek out dead animals.*  Their flowers are pollinated in a hit and miss fashion by flies, beetles and other species.  In some limited attempts to grow pawpaw commercially, growers actually hang dead fish and other lures to attract these morbid pollinators to their trees.

Zebra swallowtail - Chris Barnhart
All of these insects are important to the pawpaw but one that totally depends on it is zebra swallowtail caterpillars, Protographium_marcellusThey can only eat pawpaw leaves.  If these trees disappeared, so would the butterflies.

Zebra swallowtail egg already perched on the first unfolding leaf of the year!  REK
Megan McCarthy CC
Several years ago I was out in the woods and checking a number of pawpaw trees.   I found a few leaf buds opening and then felt the sudden thrill of discovery.  There, on a tiny unfolding leaf, sat a glistening pale green egg of a zebra swallowtail.  A female zebra swallowtail very carefully lays an individual egg on the underside of a leaf.  It seems to know that its offspring don't play well together so it lays only one egg per leaf.  When the zebra caterpillar emerges, it eats the egg case for energy, and then may eat neighboring eggs if they are available.  Since the only likely species on a pawpaw are zebras, it doesn't pay to invest the energy in eggs that will not survive.  It is interesting to contemplate how this trait occurred.


*Further information on pawpaw odors is in this paper.
Previous pawpaw blogs have covered zebra swallowtail eggs, the  butterfly's premature delivery and the Asimina webworm moth that lives curled up in pawpaw leaves.