Thursday, November 12, 2009

Arachnida!!!

Friday the 13th has a creepy connotation to some people who may believe it to be a day of bad luck. I’ll just use it as a day to talk stories about something else that some people think is creepy: Arachnids!

Arachnids are a class of invertebrates that have jointed legs. Arachnids look like insects, but a major difference is that the former has eight legs and the latter, six. This class includes spiders, scorpions, harvestmen, ticks, and mites. If you have a fear of spiders or other arachnids also known as arachnophobia, then do not proceed! I want to talk stories about some discoveries that I personally think are cool!
Crab spiders
I was admiring the beauty and appreciating the sweet smell of the oleander flowers one day. I always think about how deadly this plant is because of the cardiac glycosides, oleandrin and neriine, that they contain. Ingesting any part of the plant can be deadly to people, especially children. A closer look at the beautiful yet deadly flowers yielded another deadly agent at work! Well, deadly to other bugs, that is.

Can you see the crab spider hidden within the flowers? It is easy to miss her at first glace.
Crab spiders (Thomisidae family) are called that because they look like crabs and like crabs, they can move sideways or backwards. Their two front pairs of legs angle out and are always ready to grab their prey. They usually have flattened bodies that are often angular.
Crab spiders do not build webs to trap prey, but are hunters. Some species sit on or among flowers, bark, fruit or leaves where they ambush visiting insects by grabbing them. Some are even able to change colors to match the flower on which they're waiting.
I can't identify what type of crab spider this is. I've seen at least two kinds here. Another kind is half the size of this one with a white body and green legs. This one is ready to strike any insect seeking the oleander's sweet nectar.
Pseudoscorpions
I owe this next discovery to DJ. A few nights ago, he asked me if we had any scorpions on Saipan. I said, "yes we do" but have only seen them in pictures. DJ then told me where he could find some, and even though it was already dusk, we grabbed a flashlight and headed to the field behind his house.

He showed me where to collect them in the loose bark of a guava tree, and they were tiny! The body is about 1.5mm! Ashley, DJ's older sister remembered finding these as well when she was in grade school at Mount Carmel.
Here's a closer view where you can see the segmented body. Pseudoscorpions or false scorpions are called that because they lack the stinging tail found in real scorpions. I am sorry that I can't identify these little guys, but there are at least 5 types of pseudoscorpions in the Marianas.
Pseudoscorpions aren't dangerous to humans. They are actually beneficial since they eat a lot of other insects that we consider as pests. In fact, some of them live in books and eat book eating insects like silverfish and moths (some people call them book scorpions because of this). Because they don't have stinging tails their poison can be delivered by their pincers to kill or paralyze their prey. Some pseudoscorpions even hitch rides on flying insects, like flies, to get from one place to another!
We returned our friend back to his home soon after taking these pictures. We will now have to find some real scorpions now that we have an idea how to find them. I read somewhere that you can find them in Causarina or ironwood bark.

Well, I hope that all this talking about arachnids wasn't too creepy to you all. Until the next discovery:

Ti napu.

The Beachcomber

UPDATE November 19, 2009: A list of NMI pseudoscorpions on record can be found in the Washington Museum website. It lists 12 kinds here. The one DJ found is most likely Geogarypus longidigitatus (Rainbow, 1897). The crab spider is most likely Misumena vatia (Clerck, 1757), which is also commonly called the Goldenrod Spider or Flower Spider.

4 comments:

The Saipan Blogger said...

I found a scorpion on Forbidden Island Beach once. I've got a picture of it somewhere.

Deece said...

No offense, but this post makes me nauseous. As far as I'm concerned, there is no need for spiders in this world.

Mai said...

I'm glad I didn't see any of those "arachnida" while I was there! And, I didn't know the oleander is poisonous! (ps. long time no chat, we need to catch up sometime!)

highway_man said...

we camped at obiyan this wknd and a couple scorpions crawled out of a log we were burning.. the biggest was about 1.25 inches, 1.5 if you layed its stinger flat.. pretty interesting. didnt know we had em.