It is winter now, and orb weavers (family Araneidae) are mostly spiderlings snuggled inside cozy silken egg sacs created by their mother. They will emerge when day-length is suitably long enough, and warmer weather more consistent, for prey animals to be more common. By late June, and into October, adult Arizona specimens of the Western Spotted Orbweaver, Neoscona oaxacensis, will be abundant, especially around wetlands and fields close to water.
This is by far the most common orb weaver I encountered while I lived in Tucson, and the Sweetwater Wetlands was a great spot to find them. The species occurs from Texas to Kansas, Illinois, and Indiana, and west to Colorado, Utah, Nevada, California, and eastern Washington state. It also ranges through Mexico and Central America to Peru. They are fairly large as adults, females 11-17 millimeters in body length, males 5-12 millimeters. No two specimens are alike, though, at least in color and pattern.
Much like each zebra has its own unique pattern of stripes, so, too, do individual N. oaxacensis spiders have their own individual pattern of spots, if it has spots at all. Note among the images shown here how variable the dorsal pattern on the abdomen can be. Interestingly, the ventral pattern (image below) is much more consistent and can help place the spiders to genus in places where there are other similar orb weavers.
One study in avocado orchards in San Diego County, California revealed that spiderlings begin emerging in the first week of March, with more emergences through April. The spiders then began decreasing in number from May until late October when few adults could be found. The adult spiders do not overwinter (Pascoe, 1980).
Repairing the web, feeding, and mating, are mostly early morning or nocturnal activities, though the spiders often occupy the hub (center) of their webs during the day, too. Sometimes a spider may retire to the periphery of its web, in some kind of retreat such as a curled leaf. This can be a common behavior in regions with intense midday heat and a lack of overhead shade from a tree canopy. The spider needs to avoid overheating and dehydration from the blazing sun. The retreat may be connected to the hub by a bundle of “signal threads,” but again this is uncommon for Neoscona.
Prey consists of flying insects, especially barklice, beetles, and moths. Webs usually stretch between vegetation at a height of 1.3-1.7 meters (4-5 feet) off the ground, though I have found them at lower levels. The prey-catching portion of the webs may span from 9 centimeters to over 39 centimeters ( 3.5-15 inches), varying according to the size of the spider. Younger spiders obviously spin smaller webs.
The Western Spotted Orbweaver can occasionally exhibit large, localized populations whereby the spiders can be exceedingly abundant in a small area (Allred, 1973). Do keep your eyes open for these wonderful arachnids. There are other common members of the genus Neoscona that can be found in eastern North America, too. More on those in later posts.
Sources: Allred, Dorald M. 1973. “An unusual population of spiders in Utah,” Great Basin Naturalist 33(1): 51-52.
Jackman, John A. 1997. A Field Guide to Spiders & Scorpions of Texas. Houston: Gulf Publishing Company. 201 pp.
Pascoe, Frank Henry. 1980. “A study of Neoscona oaxacensis (Araneae: Araneidae) in commercial avocado orchards in San Diego County, California,” Avocado Society Yearbook 1980 64: 153-186.
This year I saw the last ones (adult female) in January along the Santa Cruz River / Ina Rd. A very strange winter.ReplyDelete
Wow! We haven't had much of a winter here, either, though it did get very cold a couple days ago.ReplyDelete
Wow, thanks for the info. They are one of the most popular spiders on our site...ReplyDelete
Thanks for the info. I have 1 large spider and 3 baby spider with webs in one area of my yard. The large spider is huge .. I like spiders in my garden - just didn't know kind they are. Thanks.ReplyDelete
You're very welcome, Melissa! Thank you for sharing your own experience :-)ReplyDelete
We've had six of these in the last week! I live in northern Virginia and each spider has looked very similar to the third and sixth pictures you have posted. I think I may have brought them back on my car from two weeks spent in the woods. They've built very large webs between my house and the house next door and are certainly the biggest spiders we've seen in our little corner of suburbia.ReplyDelete
Thanks for the information!
Kori: You have other, similar species out there, notably Neoscona crucifera. This is the time of year they are the most conspicuous.Delete
i have #3 from the top in my garden with its web spread between my pine and a lime. he is quite handsome with 4 yellow spots on his lower abdomen. im so happy hes here. we live in sunlakes arizona.ReplyDelete
I live in Southern Sonora, where I've spotted several of these spiders in my garden. They look much like the ones you describe but their legspan is quite larger than the one you describe, about 2 in. I could end you a pic of its belly, if you would like.ReplyDelete
I am not at all familiar with the spider fauna of Mexico; and a ventral image likely won't tell me anything conclusive. Sorry :-(Delete
Can these be kept as pets my youngest daughter said she wants an orb spider and I try and let my kids have all the pets the want so that they have the experience with all gods creatures but at same time I do t want to harm one either.. I dont like spiders myself due to bad experience kinda PTSD with them. But my kids abore them so want I g some info on them and recomidation. Any and all info would be great.. Thanks in advanceDelete
I do not recommend keeping orbweavers as pets, as tey require a great deal of space to spin the proper web, and a flight path for prey to intersect the web. Find one outdoors and watch it day after day instead.Delete
I have one of these guys living in front of my home. In fact, it is almost identical in appearance to the very first picture you have posted. I live in the Sonora Desert region of Southern Arizona in the city of Tucson. I believe that these must be very common here as another poster mentioned Ina road which is exactly the area that I reside.ReplyDelete
Nearly all of the images in this post were taken in Tucson, especially Sweetwater Wetlands. They are indeed an abundant species there.Delete
are they poisonous ?ReplyDelete
"Poisonous" means that something is harmful if ingested (swallowed). You mean to ask "is it venomous." Nearly all spiders are venomous (produce a toxin they deliver by biting or stinging), as that is how they kill their prey. Very few spiders are dangerously venomous to the average healthy human, and orb weavers are *not* among those potentially dangerous species.Delete
I have you all beat. My pet Orb Spider weaves it's web 3 feet from my front dood. One has been there every year for several years in a row. They are non aggressive and do not occupy the inside of my house. They are there for a short period of time so I don't bother them and they don't bother me. I moved one of the spiders one year to a different location in the yard. The next night it was right back by the front door. They are 6 feet off of the ground and 5 feet from the porch light. Or for the spider it's the Dinner Light!ReplyDelete
Would you be able to help me with the common name for the orbweaver I posted here... http://bugguide.net/node/view/1014929#1782625ReplyDelete
I appreciate the help!
Hi. Your image is probably of Hentz's Orbweaver. Here's my blog post about *that* species: http://bugeric.blogspot.com/2012/11/spider-sunday-hentzs-orbweaver.html. It has also been called the "Arboreal Orbweaver," and "Barn Spider" (though the latter name is shared with a completely unrelated species.Delete
I think I just had one in my house just wanted to know if I might be seeing moreReplyDelete
That would be unusual. These are almost exclusively *outdoor* spiders.Delete
I live in Oro Valley Arizona and and have 2 of these spiders in my back yard.. I also have a small puppy. Is there any concern of the spiders stinging the puppy and if so is it toxic?Delete
No species of orbweaver is considered by scientists to be dangerously venomous to healthy people or pets. Plus, the risk of being bitten by one is so remote as to be useless to worry about in the first place. Relax.Delete
i never seen them before and suddenly in the rainy season i spotted 5 in my backyard, but they are harmless and take care of mosquitoes i guess, so i let them be :)ReplyDelete
What are the predators of this spider?ReplyDelete
I have like 20 of these in my back yard. I am very scared of spiders and Im not sure if this is an orb weaver or not. I took a picture and asked google what jt was through the photo but i dont think my phone even knows lol Can someone let me send them a picture of this spider so you can let me know if that is what I have all over my yard? Im not sure how this site works. I have never been here.ReplyDelete
I have 3 of these guys at my back porch light, 2 of them are sharing a web. In the past couple of weeks they've built their egg sacs and hide there during the day. It's great to know they won't come inside. I can't wait until the babies come! Hope I can see them hatch.ReplyDelete
I was looking for information on how many can be found in one small area. I am from MI and have been traveling. Now I'm CA and I just happened to run across a "large localized population" as you mentioned. On one bush, about the size of a fiat car, I counted no less 73 spiders, both male and female, but I had never seen them before. Huge spider fan and it was obvious they were orb weavers and I thought they were mating because the males were found on the outskirts of the orb staking their claims. But it is mid summer so after reading this site I am not sure what they are doing there!ReplyDelete
I'm very scarred of them even tho they are harmless I went to a park and all in the trees I could see there eggs and everything I almost passed out thank god my mom was with me!!!!ReplyDelete
Found a vibrant one on my house in NW Tucson!ReplyDelete