Scorpion

 

This is a vicarious two-part digital field trip to Rocky Barrens Conservation Area with Kevin Firth and Chris Barnhart.  This find led me and the WOLFs on a deep dive.

They photographed this cute little creature which has the typical features of a scorpion, immediately recognizable to most of us who have never seen one in the wild.  It has a long tail with a stinger curved over the body and large pincers in front like a beached crayfish.  

This is a striped bark scorpion, Centruroides vittatus, the most common and widely distributed scorpion species in the US.  MDC says "This is the only species of scorpion in Missouri. It occurs in glades and other dry, warm, rocky areas, and sometimes in buildings and shelters and under piles of wood, brush, or garbage."

Scorpions are arachnids like the ever popular spiders, ticks and mites.They all have an exoskeleton and 8 legs unlike the insects' 6 legs.  They also have a pair of chelicerae for feeding and defense and a pair of multipurpose pedipalps.

They consume soft-bodied prey such as spiders, cockroaches, ants, crickets, beetles, and butterflies. Grabbing the prey with their pincers, they sometimes use their stinger to subdue it. 

The tail and stinger was familiar to me from childhood where every cowboy worth his saddle would encounter them in the movie westerns.  Although they had a deadly reputation on film only 25 of the 2,500 known species have venom capable of killing a human.  Usually a sting is mild although allergic reactions can cause more severe problems.  Mexico on the other hand is one of the most affected countries, with the highest biodiversity of scorpions in the world, some 200,000 envenomations per year and at least 300 deaths.*

I enjoy Fun Facts just like my 5th grade WOLF School colleagues.  Here are a few:

• Their hard exoskeleton is fluorescent when viewed under ultraviolet light.  Most species are nocturnal hunters and can be found with a UV flashlight at night.
• Unlike their other arachnid cousins, they are viviparous, meaning they give live birth.  The female hoists the young onto her back where they remain until their first molt.
• Scorpions have two eyes on the top of the cephalothorax (fused head and thorax), and usually two to five pairs of eyes along the front corners of the cephalothorax. While unable to form sharp images, their central eyes are amongst the most light sensitive in the animal kingdom, especially in dim light, and makes it possible for nocturnal species to use starlight to navigate at night! * 
  

*Wikipedia

Thanks to Kevin and Chris for the glade trip.  We hope to tag along again sometime.

Tarantula!

Chris Barnhart was hiking Rocky Barrens Conservation Area with Kevin Firth when he got these pictures of a tarantula.  Kevin goes there regularly to check on burrows that hold them, knowing which rocks to lift up where they are hiding.  

This is the Texas brown tarantula (TBT) Aphonopelma hentzi.  There are over 900 tarantula species world wide.  The MDC website says it is the largest spider in Missouri and the only species of tarantula found in Missouri versus 50 species in the US, mostly in the southwest.  The female's body length averages 2" so you can imagine the length of the legs above.

Tarantula in hole to left, note silk lining

Our TBT spends its days in its silk lined hole, predominately on rocky barren glades.  They use holes created by rodents and reptiles and provide their own lining.  Emerging at night to hunt, they predominately feed on crickets which they paralyze with venom, then chew while mixing their digestive juices with it before slurping up the liquid dinner.

After mating, the male pushes away vigorously, at times even causing her to fall on her back.  He is avoiding the female's attack as he is no longer useful except as dinner where he would be nourishing his future offspring.  He doesn't live long after that anyway so she likely considers him disposable.

She will lay out a sheet of silk and deposit her eggs with a nutritious fluid.  She then guards the egg sac and even moves it to maintain the best temperature.  Some tarantula species carry their egg sac for three months before the eggs hatch into the post embryo stage.  They remain in that sac that Cowels describes in Amazing Arachnids as "eggs with legs."  Once they absorb the rest of the egg juice they proceed to molt many times as they grow to adulthood.

Like all other arthropods, molting consists of growing a new larger cuticle under the old, then splitting out of the old outer coat with enzymes that break it down.  Molting also renews the inner surfaces, such as the mouth, as well as external and for a period of time they can't eat during each molt.  They are also softer and more vulnerable during this time.  The good news is that with molting they can regrow a damaged or missing leg. 

Fishing for a tarantula with grass

Kevin was able to draw this tarantula out with a strand of grass.  It grabbed on and he could slowly pull it out.  This requires some patience as their bodies are somewhat fragile.  They are covered with urticating barbed hairs that are stinging or irritating to the skin.  Some species can shake these loose when irritated and inhaling them can be dangerous so don't make a habit of sniffing a tarantula.

They are slow moving and near-sighted.  They sense the world largely through vibrations felt in another type of hair on their legs.  To escape they can move more rapidly but not with accuracy.   Many species are able to make sounds by rubbing their hairs on their legs together, called stridulation similar to crickets and some other insects.

*Fun fact.  Female TBT have been known to live 30 years.  Chris raised one as a pet for 10 years early in his marriage to the ever-patient Deb. 

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This is a vicarious two-part digital field trip to Rocky Barrens Conservation Area with Kevin Firth and Chris Barnhart.  Next up, the Striped Bark Scorpion Centruroides vittatus.

Red Velvet Mites

Our WOLF School field trip last week included hiking down the old Mail Trace Road looking for little things in the woods.  Almost every student found one or more of these small things crawling slowly in the leaf litter, red velvet mites ( RVM). They are also called "rain bugs" because they come out after a rain like we had earlier. 

Mites are arachnids as are spiders, harvestmen, scorpions and the ever popular ticks.  Like ticks they have six legs in the first instar, then graduate to eight legs from then on into adulthood.  RVMs are members of the Trombididiidae family of mites which gives us several thousand species to choose from.  

You can see "velvet" close up.

Their lifecycle is complicated, beginning as eggs and then several inactive pre-larval stages.  The final larvae are parasites on insects and spiders (but not us mammals!)  The adults feed on the insects or their eggs, then mate and produce eggs for the next generation.

RVM are not chiggers and it is hard to find good reputable photographs of real chigger mites. There are several species with the blood-sucking habit, the most common being Trombicula alfreddugesi.  Their larva sticks its proboscis into our skin and injects digestive juice which hardens into a tube called a stylosome, the source of the itching inflammation as described here by Missouri University.

Wikipedia

Chigger mites on the other hand are tiny, requiring a magnifier to see them.  I doubt if anyone reading this has ever seen the mite.  Only the 6 legged larval stage is parasitic, feeding on reptiles and birds. The MDC Field Guide tries to reassure us that "mammals (including people) are secondary, almost accidental hosts."

"Their presence is best known, instead, by the intensely itchy welts they leave behind, usually where your skin is thin and tender (ankles, backs of knees, about the crotch, under the beltline, and in the armpits) and where tight clothing proves an obstacle to them (as where a belt or elastic band limits their wanderings).  Chigger bites sometimes have a tiny red dot at the center, which is the remains of a scablike tube your body formed in response to the chigger's irritating saliva."

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The Bug Lady has in depth information on RVMs and their interesting mating habits at this link.