Myrmarachne colombiana is the first species of ant-mimicking spider ever found in copal (fossilized resin) from Colombia.
Myrmarachne colombiana. Image credit: George Poinar Jr. / Oregon State University.
“Ants are particularly good creatures for spiders to pretend to be — many animals find ants distasteful or dangerous to eat,” said Oregon State University’s Professor George Poinar Jr.
“Ants are aggressive in their own defense — they have a strong bite as well as a stinging venom, and they can call in dozens of nestmates as allies.”
“Spiders, meanwhile, have no chemical defenses and are loners, which makes them vulnerable to being hunted by larger spiders, wasps and birds — predators that would rather avoid ants. So if a spider can be like an ant, it’s more likely to be unbothered.”
Myrmarachne colombiana was found in a type of fossilized resin known as copal.
“Copal is a less mature form of fossilized resin than amber, which is routinely dated to be 25 million or more years old. Still, copal can be up to 3 million years old,” Professor Poinar said.
“The age of the resin in this case, however, could not be determined.”
“The resin block I was working with, which came from Medellin, Colombia, was too small to age-test without risk of damaging the spider inside.”
According to the study, there is no record of any currently living ant-mimicking spider making its home in Colombia.
“It is a challenge for spiders to accomplish this magical transformation to ants. Ants have six legs and two long antennae, while spiders have eight legs and no antennae,” Professor Poinar said.
“To get around those anatomical differences, spiders typically position their two front legs in a way that approximates the look of antennae.”
“But number of legs and absence/presence of antennae are not the only characteristics differentiating an ant’s appearance from a spider’s.”
“The abdomen and cephalothorax of spiders are closely attached, while in ants the equivalent of these body parts are separated by a narrow segment called the petiole.”
“And there are many other lesser structures that need to be modified in spiders for them to closely resemble ants. How is this accomplished? Most scientists say it begins with spider mutation, adaptation and then natural selection.”
“However, I think there is some spider reasoning and intelligence involved too since the spiders often model their body changes after specific ants in the same environment.”
“In the early days, we were told that all habits of insects were the result of instincts, but that is no longer the case.”
“Several groups of spiders have developed the ability to look and behave like various types of ants, he added. There are also spiders that try to blend in as other insects, such as flies, beetles and wasps.”
“Most of the copycat spiders belong to a few families of hunting spiders, including Salticidae or jumping spiders. The specimen in the Colombian copal appears to be a jumping spider.”
“Spiders that practice mimicry also come from the Corinnidae (sun spiders), Thomisidae (flower spiders) and Zodariidae (spotted or ant spiders) families.”
The study was published in the journal Historical Biology.
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George Poinar. Myrmarachne colombiana sp. n. (Araneae: Salticidae), a new species of ant-mimic spider in copal from Colombia, South America. Historical Biology, published online March 7, 2024; doi: 10.1080/08912963.2024.2320190
Source : Breaking Science News