This week we visit a spooky spider just in time for Halloween. Arachnophiles, spider lovers, may recall a story that made headlines two years ago when anWebs of social spiders cloak a spooky tree. click *here* to see a larger image.
enormous spider web was discovered in Lake Tawakoni State Park in Texas. This leviathan enshrouded several trees along a trail. Scientists concluded that it was the work of legions of spiders from at least twelve different families of spiders. A few weeks ago I happened upon a similar massive web enshrouding a forty foot elm tree on the Little Patuxent River near Columbia, Maryland. The creepy gossamer web was composed of scores of smaller webs encasing almost every branch of the tree and spilling onto smaller trees and shrubs nearby. Each small web was filled with adult and juvenile cob-web spiders, Anelosimus studiosus, and the remains of planthoppers, flies, and other small insects - former meals of the hungry horde. It was an eerie, magnificent sight to behold. Spiders are ferocious predators and cannibals known to eat their kin. Why then would a spider risk being eaten by brother, sister, or mom while sharing a web?
Scientists learned that some species of cob-web spiders like Anelosimus studiosus gain significant advantages from communal life. By transplanting spiderlings, researchers discovered that young spiders placed in the web of their birth were more likely to survive and developed quicker than those forced to spin webs of their own. Building and occupying large communal webs enables social spiders to capture more prey than they might if they occupied smaller webs of their own. Researchers also discovered that social spiders cooperate in subduing large prey that might be difficult for an individual spider to kill.
Except for eating an unhatched egg every now (who can resist an omelet), female Anelosimus studiosus are pretty darn good mothers as well. For protection, each female Anelosimus studiosus encases her Thousands of spiders large and small scurry about the webs. click *here* to see a larger image.eggs in sacs made of tough silk. After tiny spiderlings hatch, escaping from the sac is an essential but challenging task. Fortunately, mom and other females living in the colony tear and puncture the silken sac thereby enabling youngsters to emerge and move about on their own. To further assure the success of their young, some species of social spiders feed their spiderlings by regurgitating food much the same way a mother bird feeds its nestlings. So, by setting aside an instinct to eat whatever moves, including one’s relatives, communal spiders enjoy the benefits of life in the big web.
Bug of the Week thanks Dr. Jeff Shultz for identifying our social spiders and Tara Boyle and Sam Litzinger for providing the inspiration for this episode. Two awesome spider studies “Delayed juvenile dispersal benefits both mother and offspring in the cooperative spider Anelosimus studiosus (Araneae: Theridiidae)” by T. C. Jones and P. G. Parker and “Mechanisms underlying egg-sac opening in the subsocial spider Anelosimus cf. studiosus (Araneae: Theridiidae)” by C. Viera, S. Ghione, and F.G. Costa served as references. To learn more about big spider webs and social spiders in general, please visit the following web sites.