Tinier than poppy seeds, spiderlings just hatched from their egg sac are often seen in a tight, huddled cluster.
Spiderlings huddle together just after hatching. Seattle Times photographer Steve Ringman shot this picture this week on the Sammamish Plateau.
Just why they huddle up like that isn’t known, said Rod Crawford, spider expert at the Burke Museum. To me, it looks like they are chilly and want somebody to throw on a down quilt.
When they scatter, that, Crawford notes, is not to disperse to new habitat, but to defend themselves from some perceived threat. They may, or may not regroup, so to speak, after the scare has passed.
Spiderlings disperse if they feel a threat at hand.
Steve Ringman photo
Watching them, Ringman said the spiderlings looked like the tracery of popped fireworks — an image I can see perfectly in my mind, because the pace of the explosion of firework sparks is just the same as the scatter of the spiderlings … poof!
When I asked Crawford if they were ballooning to a new place, he thought not. To him, this species looks like a European cross spider, an orb weaver, an invasive species that is virtually the only orb weaver found on vegetation in urban and suburban yards in our area.
Spiderlings do often balloon, but “this species is not a very big-time ballooner,” Crawford wrote in an email to me. “It disperses more often by crawling and by being transported by humans planting nursery stock instead of using the perfectly good plants Mother Nature put on their property. Some other orb weavers balloon much more often than this one. Microspiders, wolf spiders, etc. balloon most of the time. At any rate, ballooning is a very efficient (though very risky) form of dispersal, something all organisms need to do if they are not to be confined to the one spot on earth where they first evolved.”
The time of year of dispersal by ballooning varies by species, as does the number of egg sacs and eggs. Araneus diadematus (the cross orb weaver) seldom makes more than one egg sac, usually in the fall. The eggs hatch before winter, but the spiderlings remain inside the egg sac usually until about May 1, “but there have been great delays this year thanks to our miserable spring,” Crawford notes.
To learn more about spiders, see Crawford’s Spider Myth Website .
For a beautiful account of ballooning spiders, read this account, The Aeronautic Flight of Spiders, written in 1877 Proceedings of the Academy of the Natural Sciences of Philodelphia: