#theridion

[razehider]

a Theridion mom guarding her jelly children. spiderlings disperse quickly and eggs are often hidden in vegetation or under bark or rocks, but when it comes to theridiids you can reliably find some on literally any human infrastructure imaginable as long as it's three-dimensional

(June 11th, 2025)

[drhoz]

#3664 - Theridion zantholabio

A combfooted spider found across much of New Zealand.

It was first described by Swiss-born naturalist Arthur Torrane Urquhart 1886, and named for the yellow lips, presumably.

Queenstown, NZ. I saw this one on the last trip, but didn't get an ID until recently. On THIS trip, we only stopped in Queenstown long enough to pick up an external harddrive for all the photos I was taking.

[onenicebugperday]

@avendesura submitted: Hi, I LOVE your blog - its definitely helped me face my fear of insects! These 4 little cuties have been living in my window sill for a couple months and i was wondering if you could tell what they are? (and are those little balls eggsacs?) I'm in Southwest Florida. Thank you!!!

Thank you, I'm so glad it's helped with your fear! They do look like egg sacs, yes. I can't tell what the spider is without closer/clearer photos since it's toooooo tiny to see any details. The most specific I can get is probably a cobweb spider in the family Theridiidae, and mayyyyyyyyybe a tangleweb spider in the genus Theridion.

[drhoz]

#1860 - Theridion sp. - Tangle-web Spider

Photographed by me, in Banjup, Perth. 

A large genus with some 600 described species around the world. Notable examples include the Hawaiian happy face spider T. grallator, named for the symbol on its abdomen, and T. nigroannulatum, one of few spider species that lives in social groups, and dogpile prey.

[yangrina]

I found this little girl a while ago under my window and had to move her and her egg sac. I'm happy to see that almost all babies hatched 😄 now i can release them soon again 😊 #spinne #webbing #spiderwebs #spider #spidersofinstagram #spidergram #instaspider #theridion #melanurum #eggsac #spidersac

[britsnana2]

7/4/14

Order Araneae- Cobweb spider- Unknown -Theridion- Female -adult 4mm

She ate a green caterpillar!!

[libutron]

Happy-face Spider

Although this charismatic spider is scientifically named Theridion grallator (Theridiidae), certainly is better known as the Happy-face Spider because of the interesting color pattern on its abdomen, which closely resembles a smiley face.

Endemic to Hawaii, this species is found in the rainforest from O’ahu to the Big Island. However, they are very hard to find due to its extremely small size (about 0.6cm long).

Theridion grallator is highly variable for color and shows diverse morphs, the frequencies of which are very similar among populations, although the genetic basis for them differs between islands. The most common color morph is yellow, which makes up about 70% of any population. The other 30% is composed of “patterned” morphs generated by patches of red, white, or black pigments superimposed on a yellow background. The common name happy-face spider comes from the pattern of red and black shown by the color morph named "Red front".

The yellow background of any morph can be modified through ingestion of highly pigmented prey. 

The "Yellow" morph, the most abundant, is highly cryptic and very difficult to see against the filtered green light that penetrates the leaves under which the spider lives. This, in conjunction with morphological and behavioral attributes, suggests that predators do represent an important selective agent in the species.

This spider exhibits behaviors that are extremely rare amongst spiders. One of the more interesting is maternal care, a behavior that is exhibited by less than 1% of all the spiders species on the planet.

References: [1] - [2]

Photo credit: ©Stuart Wilson | Locality: Hawaii

[sciencetoastudent]

New spider species discovered by USU students | KSL.com

By Morgan Jacobsen

LOGAN — Stephanie Cobbold and Lori Spears knew they had found something rare. A spider they had collected while earning Ph.D.s in ecology at Utah State University wasn't fitting any description in their species identification keys. But they knew the odds of discovering a new species in Utah were slim at best, and the two researchers weren't about to get their hopes up. Cobbold and Spears sent the spider to Herbert Levi, an arachnid classification expert at Harvard. Months later, he had the answer. "He said, 'Yes, it's a new species,'" Spears said. The Journal of Arachnology ratified the discovery in November in an official description of the spider, which bears the name Theridion logan after its discovery in Logan Canyon. "I was very, very excited," Cobbold said Friday. "Discovering a new species is something that many biologists dream about." So far, the spider is known to exist in Cache County's Green, Logan and Blacksmith Fork canyons — and nowhere else, according to Cobbold. Spears says finding a new species in Utah is especially significant because most new species are discovered in tropical areas, which have greater biological diversity. "When new species are found, we usually think of areas that are remote and not well-studied," Spears said. "We basically found this spider right next door to campus. It goes to show that new species can even be found in our backyard."

At only 1 to 2 millimeters long, Theridion logan is black and white with a series of chevron shapes on its abdomen. Although the shrub-dweller is in the same family as the black widow, it poses no threat to humans, Spears said. Spears says the spider wasn't classified until now probably because it was either misidentified or it wasn't collected by researchers. Though the spider appears to have a limited range that is frequented by recreationists, Cobbold said there is no immediate cause for concern. "Some people have expressed concern that parts of the canyons ... might become closed to the public to protect this new species," Cobbold said. "We do not have nearly enough information to know whether Theridion logan truly has a restricted range or not, and we have no evidence suggesting that this spider is affected by recreational use of the canyons." The discovery indicates there is still much to learn about Utah's wildlife, Cobbold said. "This new spider suggests that other species remain to be discovered, which is exciting," she said. "Given that this spider was found near the city of Logan, I would imagine that there must be several other undescribed species in the more remote parts of Utah." Cobbold and Spears made the discovery while studying spider communities at USU. Spears continues to work at the university as the coordinator of the Cooperative Agricultural Pest Survey and Cobbold just finished working as a biologist for Idaho Fish and Game.