Arachnida

Arachnids


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Arachnida

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Cyrba algerina
Cryptocellus goodnighti
Maevia inclemens
Aelurillus luctuosus
Gluvia dorsalis
Micrathena gracilis
Dolomedes
Dolomedes
Amblyomma americanum

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Classification:

General Description

GeneralDescription

Source and Additional Information
Author
Phil Myers, Museum of Zoology, University of Michigan
Rights
©1995-2008, The Regents of the University of Michigan and its licensors
Indexed
September 07, 2010
Citation
Myers, P. 2001. "Arachnida" (On-line), Animal Diversity Web. Accessed September 05, 2010 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Arachnida.html. 

   

This large Class of arthropods includes over 60,000 described species (and most likely a very large number of so-far undescribed ones). Spiders make up the majority of these (over 50,000 described species); with mites and ticks next largest (around 48,200 species). The Arachnida also includes a diverse array of smaller groups, including scorpions (1200 species), whip scorpions (100 species), palpigrades (60 species), pseudoscorpions (2000 species), solpugids (900 species), and harvestmen (5000 species). Nearly all species are terrestrial.

 

Arachnids have a pair of tagmata called a prosoma and opisthosoma. The prosoma is partially or completely covered with a carapace-like shield. The opisthosoma may be segmented or unsegmented. The appendages on the opithosoma are absent or modified, being used as spinnerets (spiders) or pectines (probably sensory in function, found in scorpions). Respiration is via tracheae or book lungs; it is cutaneous in many small arachnids.

 
 

Sources:

 
     
  • Hickman, C.P. and L. S. Roberts. 1994. Animal Diversity. Wm. C. Brown, Dubuque, IA.
  •  
  • Brusca, R. C., and G. J. Brusca. Invertebrates. 1990. Sinauer Associates, Sunderland, MA.
  •  
  • Pearse, V., J. Pearse, M. Buchsbaum, and R. Buchsbaum. 1987. Living Invertebrates. Blackwell Scientific Publications, Palo Alto, Ca.
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The information highlighted in yellow below has not been reviewed.

Pholcus phalangioides

Source and Additional Information
Supplier
Nancy Landrum
Indexed
November 04, 2009

I couldn't find him in the list of arachnids, I know the fault is mine being so fascinated by the other spiders that I became distracted. I had never see one of these, what I all clown spiders because of the way they spin and vibrate their webs when disturbed, and I originally saw them at my Mothers house only a couple miles away. At that time we were building an addition on the house, and the only thing that separated the new crawl space from the basement was insulation. Of course no vents had yet been installed on the block work of the addition so our house became the camping ground of every sort of spider,including the giant Huntsman, which were beyond my ability to tolerate. While working on the drywall, a Huntman came crawling over the wall, and in my panic, I dumped a blob of joint cement on a broom, covering him with it as the broom transported him back out an open window. Two hours later, I looked out the open window, and this magician of a spider was trying to get back in almost completely free of the joint cement. Later on I started to notice that these "clown" spiders had come to my house, and my husband said one day, that the only spiders he ever saw anymore were the Pholcus phalangioides. But by this time the huge opening had been secured in the basement, so I doubt if "clowny" would be much of a match for the royal Huntsman. I fear spiders with all my heart, but this little guy became my best friend, and when his numbers dwindle in the winter I fear he won't come back or survive. I have gotten up in the morning and found their webs in the corner of the couch with one just sitting there. I have also had them come very close to using me as a web anchor, I wonder about their eyesight, but the lighting attacks from them I have witnessed on larger spiders is amazing. I watched one baby that was so tiny he was barely visible race to attack a large black spider on the wall. It was like Pholcus phalangioides, the baby appeared from nowhere and went right towards the big spiders mouth. The big spider didn't move as I think he was shocked, but the baby retreated for a bit and I got the big spider out of the house. I have watched them strum the webs of other spiders trying to trick them, but the most amazing sight I saw was I had a small black spider in a corner who had just hatched a bevy of babies. This web went into a cone shape about one foot from the woodwork. I saw these tiny white spiderlings working up the web towards independence, and of course I was really enjoying this unfolding of new life, when all of a sudden I noticed one of the white babies was already to the very top of the web, and on closer inspection discovered it was a baby clowny, and next to him in a pot of artificial flowers sat two large Pholcus phalangioides, like the baby was sent on his first mission. I cherish these clown spiders as my best friends because the look like nothing and I have found web encrusted leftovers that were so large, the fangs were all that were visible, so I know they are doing their jobs. If I see a strange running spider hide under a rug, my first instinct in to track him down with Hotshot, but I realize he won't last long anyway, so I pity him. I know this is just a human interest story, but I have watched them just spin webs so fast to catch prey, and the most certainly don't bite the prey first, so the poor critters are totally aware of their fates.
References
  • Observation of this remarkable species.
"Arachnida". Encyclopedia of Life, available from "http://www.eol.org/pages/165". Accessed 09 Sep 2010.