Jaws – Spidey Galore #1

June 4, 2010 at 11:22 am | Posted in itchy fingers | 1 Comment
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Ever since Itchyfingers saw that Leaf Insect nymph, we had become more and more interested in insects and macro photography. Through magnification of the lens, we were then able to pick up details of the insects which would otherwise go unnoticed with the naked eyes. Only then would you be able to appreciate these tiny creatures more. 🙂

As we look more carefully in parks and gardens, we were amazed by the number of different insect species, especially that of the spiders. Well, strictly speaking, we all know spiders are not insects. All insects have six legs while most spiders have eight. Spiders belong to the group Arthropods, which have jointed legs and an outer skeleton whose components include a horny substance called chitin. They have no wings or antennae but have a spinneret, the silk-spinning organ.

One of the most interesting things about spiders is their ability to mimic. Like other insects that display mimicry, spiders also mimic ants.


At a glance, this looks like an ant, with the typical head, thorax and abodmen
as well as long slender legs. The forelegs are often raised in the air like a
pair of antennae


But look at the numbers of legs…and the eyes! Eight for both! This is from
the Jumping Spider (Salticidae) family


You can see the four pairs of eyes clearer here


Jumping spiders have unique eye arrangement. “Viewed from the top, the
eyes are arranged in three rows – two pairs in front, a pair of usually tiny
ones in the middle, and another pair further back. This arrangement allows
them to have an almost 360 degree field of vision. Two of the four eyes in
the front row are typically enlarged and have certain anatomical features
which give the spiders a telephoto system. The lateral eyes function as
stereoscopic wide-angle lenses. Together, the eyes allow the spider to
detect movement, recognise their prey, and judge distance accurately before
they pounce for the kill.” – A Guide to the Common Spiders of Singapore,
by Joseph Koh

So which ant does it mimic?


The
Common Spiny Ant (Polyrchachis sp.), also called the Golden Backside
Ant or Golden-tailed Spiny Ant. This ant moves constantly and it is so
difficult to take a decent photo of it!


This one we saw was the Giant Ant-like Jumpe
r (Myrmarachne maxillosa).
Just look at the humungous jaws! It makes the spider look like a heavily
fortified soldier ant. This is a male, with total length ranging from 5.5 -8 mm
and 7.5 – 12 mm if including the jaws


Jaws opened! Looked scary!

So why do these spider mimic ants? According to the guidebook, it says that “spiders deceive their ant-models and prey either on the ants themselves, or on the hotmopteran bugs ‘tended’ by the ants. However, ant-mimicking Jumping Spiders in Singapore have never been observed to have attacked the ants they imitate.” No wonder we saw so many of the Spiny Ants crawling around, none hunted by the spider…


The much smaller female. We had initially thought that this was the male, as
some other species of spiders have larger females than males. So we thought
it was funny when one of the Spiny Ants went close to ‘him’, ‘he’ quickly ran
off immediately! Maybe it was because ‘he’ was smaller in size…but it was
really funny!
😀


The female looks even more like ants…Mimicking ants may be a form of
self-protection, as predators like the spider-hunting wasps and birds
generally will avoid ants cos they secrete distasteful formic acid when attacked

So now you agree that spiders are interesting? Itchyfingers have more to share, do come back for more! 😀

Also see related posts:
> ‘Leaf’ Me Alone
> Masters of Disguise and Camouflage
> A Visit to the Hospital
> Attaining Immortality – Body Preservation

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  1. pretty image


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