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A Guide to Common Singapore Spiders
by Joseph K H Koh
  Ant-Mimicking Jumping Spiders
Myrmarachne and Agorius
 
close-up of black ant mimic
Myrmarachne maxillosa waving
its front legs in mid-air
Some Jumping Spiders assume the appearance of an ant by having long and slender legs and what appears to be a three-part (head-thorax-abdomen) body of an insect. To add further to the deception, the fore-legs are often raised in the air like a pair of antennae.
Some scientists believe that by mimicking ants, the spiders deceive their ant-models and prey either on the ants themselves, or on the homopteran bugs "tended" by the ants. However, it should be noted that the ant-mimicking Jumping Spiders in Singapore have never been observed to have attacked the ants they imitate. A more plausible explanation is that by copying the physical appearance of ants, the ant-mimicking Jumping Spiders are actually buying insurance for self-protection, since spider-hunting wasps, birds and other spider-predators generally avoid ants which secrete the distasteful formic acid when attacked.

There are two genera of anti-like Jumping Spiders in Singapore. The more common Mymarachne have a long waist (pedicel) and an elongated cephalothorax with a constriction dividing the higher cephalic region and the lower thoraxix part. The jaws of Myrmarachne spider, especially the males, are enormously enlarged and project in front making the spider appear to be a soldier ant.
close-up of brown ant mimic with large jaws
The enormous jaws of a male Myrmarachne plantaleoides
The cephalothorax of the spiders of the genus Agorius is also divided into distinct "head" and "thoracic" regions but the division is not as obvious as that shown in Myrmarachne. The most diagnostic feature of Agorius spiders is that the first pair of legs are exceedingly long. The third last segments (patella) of the fore-legs are conspicuously more elongated than those of other spiders.
close-up of brown ant mimicThese Myrmarachne spiders copy different species of "red ants". Take a closer look and note the differences. Check the following:
  • Colour of the "head".
  • Colour of the abdomen.
  • Constriction, if any, at the abdomen
close-up of black ant mimicclose-up of reddish ant mimic

For more about ant-mimicking Sac Spiders Castianerira and Apochinomma.
Here are a few species of
ant-mimicking Jumping Spiders
found in Singapore...
close-up of black ant mimic with large jaws

close-up of black ant mimic close-up of black ant mimic with large jaws
  From "A Guide to Common Singapore Spiders" by Joseph K. H. Koh
BP Guide to Nature Series published by the Singapore Science Centre and sponsored by British Petroleum
© 2000 Joseph K H Koh