This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
[caption id="attachment_115" align="alignleft" width="222" caption="Ant, or Spider? You Decide! Top: Sandilya Theuerkauf; Bottom: Sean Hoyland (both from Wikipedia Commons)."][/caption]
Myrmecomorphy
Part of the fun in natural history is playing word detective! Naturalists speak in greek and latin and love mashing together parts of these languages to create new, yet often very descriptive, words. This month, I want to talk a little about an awesome word - MYRMECOMORPHY.
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This beauteous etymological wonder is derived from from the root words myrmex, meaning ant, and morphos, meaning form. Soooooooo, myrmecomorphy is ant-mimicking! This is a form of Batesian mimicry, which occurs between two, often very different, species are very similar in appearance. The caveat is that the initial species is usually toxic, spiny or otherwise unpleasant to eat, while the mimic is a fraud and only appears to be dangerous.
In the two photos at left did you spot the real ant? If you count the legs it's easy to tell. The individual in the bottom photo has eight legs whereas the top 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 spider family) literally means ant-spider and is characterized by these fraudulent mimics with nearly 200 species of ant wannabes, and for good reason!
While ants are nice, tiny little "fun-size" prey-items, they are typically quite dangerous to eat and mighty unpleasant to the palate. Therefore, a wide variety of potential predators of the Myrmarachne, including other salticid spiders and preying mantises, leave them well alone! Prey preference experiments have shown that these predators are not just averse to chomping on ants, but they avoid the Myrmarchne just the same.
Jumping spiders have complex mating behaviors. Nelson & Jackson describe in detail the mating behavior of the mimics Myrmarachne assimilis and M. bakeri. Its quite the romance novel so let me set the mood...
(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 as if out a dream, she appears before his eyes - all of them. The morning dew glistens off her abdomen, four eyes catching the sunrise to the east. He arches his palp, twitches his abdomen... standing erect. She faces him, eagerness dripping off the hairs of all eight legs, waves her palps gingerly in the air. He watches with the utmost anticipation. She turns away, he follows. She turns around, he waits. Eyes locked. Her cephalothorax lowers, he dances with the rising sun as if beckoning the light to share in this moment.
She lunges past him, yet is blocked by his desire. Eight eyes staring. Eight legs trembling. Two hearts melding. She tries to leave, but his approach calls to her as a primal scream. She must answer. His legs erect, brushing up against hers. She wants to run away, escape from these feelings, yet can’t seem to pull herself away. The hypnotic, primordial 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
[caption id="attachment_116" align="aligncenter" width="550" caption="Left: Oecophylla smaragdina, Right: Myrmarachne plataleoides (female). Photos by Chih Fah Shin."][/caption]
Nelson, X., & Jackson, R. (2007). Complex display behaviour during the intraspecific interactions of myrmecomorphic jumping spiders (Araneae, Salticidae) Journal of Natural History, 41 (25-28), 1659-1678 DOI: 10.1080/00222930701450504