Jumping spider shows mammal-like behaviour
Meet the arachnid with a difference – it looks like an ant and suckles its young.
T here is a species of Asian jumping spider, Toxeus magnus, that mimics unpalatable ants to escape the attention of predators. But when Zhanqi Chen, a biologist at Xishuangbanna Tropical Botanical Garden in Yunnan, stumbled upon a silken T. magnus nest and peered inside, he realised there was something even stranger going on.
“There were five very large individuals in there,” says Chen. “This is very unusual, because jumping spiders are not sociable, and the young leave their mother straight after hatching. This made me very curious.”
Further investigation revealed that the spiderlings remain in the nest for 20 days, during which time the mother feeds them with a milk-like substance secreted from her abdomen. At first, she deposits droplets of the ‘milk’ around the nest, from which her young drink, but as they grow, they start to suckle directly. Even once they have dispersed, the spiderlings return regularly to suckle for another few weeks.
Why, of the many thousands of jumping spider species out there, should this one do things so differently? “The adults are similar in size to the ants they mimic, but the young spiders are too small to look like the ants even though their body shape is similar,” says Chen.
In which case, the spiderlings should stand a better chance of survival if they remain in the nest until they are big enough to look like ants.
But to reach that size, they need sustenance. The spider ‘milk’ contains four times the protein of cows’ milk. Because the liquid is exuded from the female’s genital opening, Chen suspects it is derived from the same nutritious stuff with which females provision their eggs. Indeed, other spiders are known to provide hatchlings with a batch of non-viable eggs as a first meal before they disperse.
Meanwhile, Chen is keen to investigate whether the mother spider provides more than just milk during this prolonged period of parental care. “Perhaps she also teaches them how to care for their young,” he says. Stuart Blackman
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