Huntsman spiders (Araneae: Sparassidae) are one of the biggest families of spiders. There are 1,319 species living in many countries across the world, with habitats ranging from deserts to rainforests and even caves.
To complement their diverse living arrangements, they have a diverse family life to match, with some members of the family happy to indulge in a spot of cannibalism. However, one particular species, Delena cancerides, shows a surprising tolerance for sharing her living space with her spiderling offspring, according to new research.
The findings are published in the journal Molecular Phylogenetics and Evolution.
“Cannibalism might happen occasionally, but with Delena cancerides, it’s almost never,” behavioral ecologist Linda Rayor of Cornell University told Science News.
Even the most tolerant of spider moms can have their off days, though as Rayor says, female Delena cancerides are more likely to attack male spiders that stick around too long after they've laid their eggs.
What makes this species truly unique is the caring qualities that D. cancerides has for her offspring. While some may argue that this spider isn’t truly social, she’s not truly solitary either.
The species is not web based, preferring to live under sheets of bark that have pulled away from the tree or under rocks that have a small crevice. While most huntsman are solitary hunters, who care only briefly for their eggs and new offspring, five species have been observed to live in groups with longer-lasting parental care. These groups consist of an interactive family group with a single adult female spider and her immature or just matured offspring. These spider families may remain together for as long as a year depending on the species.
Juvenile spiders go through developmental stages called instars as they reach maturity. For most huntsman species the spiderlings will reach adulthood in their tenth instar, but disperse from their hatching place long before. D. cancerides spiderlings like to stick around with their mom until they disperse in either their ninth or even tenth instar.
D.cancerides behavior is characterized because her home will be filled with her offspring from multiple clutches, all at different stages of instar development. They share prey and most importantly don’t eat each other, as they all live together in the same space.
Most offspring of a solitary huntsman start to forage for themselves in their first instar, but the offspring of the five social huntsman spiders emerge from the egg sac with yolk-filled bellies and do not feed until they have grown up a bit and molted into their second instar.
The authors of the new paper hope to learn more about social behavior and parenting in these Deleninae spiders.
All Deleninae females chew a hole in their egg sac for their young to come out of, but why these five species stop there and don’t indulge in the cannibalism of the solitary huntsman remains to be seen.
Correction: An earlier version of this article incorrectly stated that D. cancerides live in cracks and holes in tree bark. This has been corrected to reflect that they live under sheets of bark or rocks with a small crevice