Nature Blog Network

Wednesday, September 19, 2007

Ant? Spider? You Decide!

During the course of my blogging here, I have become somewhat of a fan of spiders. My previous posts on spiders have focused on their unusual characteristics, such as doing the booty drop, showing off a little bling bling to catch the ladies eye, cutting off a leg to escape predators, and checking their web stats. I have developed an appreciation of spider diversity and behavior through reading papers that have caught my attention for this blog.

One of the reasons I absolutely adore the theory of evolution is that its predictive power can be so wonderful. The results of selection so wondrous in and of themselves. I am familiar with many aspects of symbiosis, having co-taught a class on the subject with my advisor (I covered mammalian herbivore digestion, termites, wood-eating bivalves, and bioluminescence) and working on the ecology of animals with chemoautotrophic bacterial endosymbionts for my dissertation research. I have seen alot of strange and unusual adaptations, but they just keep getting stranger and stranger the more I delve into the fantastic world of evolution and behavior. With this I now bring you the word of the week:

Its a fantastic word brought to my attention by a recent paper published in the Journal of Natural History by Nelson & Jackson. What does this word mean? The root words "myrm", "eco", and "morphic" refer to ant, home(Aydin suggests eco may derive from echo meaning repeating, which makes more sense than deriving from oiko meaning home) and form respectively. Hence this refers to species that are an "ant-repeating form".As Christopher from the Catalogue mentions in the comments below, the most plausible definition is from the roots myrmeco- (derived from myrmex, "ant") and morphic ("form"), meaning ant-form or ant-like.

Top photo by Sean Hoyland and bottom photo courtesy Sandilya Theuerkauf, Wynaad, 2006, both from Wikipedia Commons.

This is a form of Batesian mimicry, which is between 2 different species that look very similar. The caveat is that one species is usually toxic, spiny or otherwise not very pleasant to eat, while the mimic is typically a fraud in the arena of danger. In the two photos above did you spot the real ant? If you count the legs its easy to tell. The individual in the top photo has 8 legs whereas the bottom photo is the Weaver Ant, Oecophylla smaragdina, the queen nonetheless. The mimic is Myrmarachne plataleoides (female shown in photo, males have gigantic mandibles, about 33% of their body length).

The spider genus Myrmarachne (Salticidae - the jumping spiders) is characterized by these fraudulent mimics with nearly 200 species of ant wannabes.
Ants are dangerous and unpalatable prey-size organisms and a variety of would-be predators of salticids, including other salticids and mantises, avoid making predatory attacks on, or coming close to, ants. Experimental studies have also shown that salticids and mantises that are averse to attacking ants are averse to attacking Myrmarachne"-Nelson & Jackson 2007

Top: Oecophylla smaragdina, Bottom: ant wannabe Myrmarachne plataleoides (female). Photos copyright Chih Fah Shin

As I've shown with other jumping spider posts (see links in first paragraph) they have quite complex mating behavior. Nelson & Jackson describe in detail the mating behavior of Myrmarachne assimilisand M. bakeri. Its quite the romance novel. Visualize a hot steamy jungle next to a white sand beach, a gentle breeze, seagulls laughing in the distance...

He's alone, walking through the brush and then he sees her. The morning dew glistening off her abdomen. Her four eyes catching the sunrise to the east. He arches his palp and twitches his abdomen, standing erect. She faces him, waves her palps in their air as he watches with anticipation. She turns away, he follows, she turns around, he waits. Her cephalothorax lowers, he dances in response, she lunges past him, yet is blocked by his desire. Eight eyes are staring. She tries to leave, but his approach beckons her. His legs erect, they brush up against her legs. She wants to run away, escape from these feelings, yet can't seem to pull away. The power of lust overcomes all her senses. She shifts her abdomen closer, he gently places his chelicerae upon her abdomen. Softly, calmly, he applies each palp once, then its over.
"When the male disengaged his applied palp, he moved over the female (her abdomen no longer raised or rotated), tapped and stroked and then, once positioned again beside the female, the male scraped his palp across her now flexed-up and rotated abdomen and resumed copulation. Before next palp application, while centered over the female, the male sometimes stepped backwards and forwards, stroking and tapping intermittently."-Nelson & Jackson 2007


  1. The picture of Myrmarachne definitely wowed us here at work. I'm especially impressed by the fake constriction in the prosoma to make it look like it has a separate thorax. And when you realise that the eyes are all hidden in the front, and the big "eyes" that you can see are actually eyespots...

    Things like this are why I'm a biologist.

  2. Ah, I missed the 8 legs of Myrmarachne. I thought those were antennas.

    Incidentally, the eco in Myrmecomorphic probably comes from echo, meaning to repeat.

  3. Christopher, The constriction is amazing. It also took me a while to look for the eyes. Its unbelievable stuff. Jumping spiders are supposed to have image forming eyes by the way.

    Aydin, I was a bit confused about the eco part. This would make sense. I thought that eco was a derivative from oiko meaning home. But it doesn't fit well with the other two words myrm and morph. So ant-repeating-shape make a lot more sense! I changed it in the text. Thanks!

  4. Sorry, Aydin, Kevin, but you're both wrong. There's no 'eco-' in 'myrmecomorph', there's a 'myrmeco-', the connecting form of 'myrmex', Greek for an ant. Take a look also at 'myrmecophage', an animal that eats ants.

  5. Dearest Kev, you are so jealous of these ants aren't you. They have babies too though, ya know.

  6. I've seen ant-mimicking salticids up in North Queensland, where they're pretty common.

    They're very good mimics but you notice them first because there's something not quite right.

    Getting close enough to suss out what's odd can be a trial though --- green tree ants are feisty little devils.

  7. Thanks for the 8 LEGGED miracle! But I think I found something new here in INDIA - Mumbai (Bombay)! An ant species with 8 legs and two antennas! Well tha makes full five pairs of external limbs!!
    Friends and me are still trying to figure it out the whereabouts and habits of this species. Pictures are in the pipeline soon...

  8. Interesting Ayub. Make sure you let me know when you have pictures available please!


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