cs16-levi's Journal

Please take care when clicking the "Agree" button on someone else's ID (especially the Computer Vision / Auto-ID)

When you click agree and an observation becomes research grade it becomes available to researchers and false data can be extremely frustrating to them. "Research Grade" observations are also used to train iNaturalist's Computer Vision, so incorrectly-identified RG can mess up iNaturalist's map data and the Computer Vision for users who will use it later.

Research grade isn't a special reward for your observations. If you can't id something further thats perfectly fine.

When you click the "Agree" button, you are indicating that you believe it to be that species, based on your personal knowledge or research. It is important to remember that quite often most insects and spiders cannot be identified without microscopy. (The use of a microscope)

Furthermore, Some people’s identifications are more reliably correct in some taxa, so it seems like an easy shortcut to check how reliable the person seems and choose to agree or not agree based on that. Nobody is 100% reliable in any taxa. If you instead check the direct evidence (the photos, location, date/time, etc.) and arrive at an identification based solely on that, then the reliability (or unreliability) of the previous identifiers won’t, and can’t, have any effect on your answer.

That kind of independent identification is way, way more valuable than quickly clicking “Agree”, because it can be used to correct errors. It’s kind of like doing a long math homework question, writing down the answer, then throwing out your previous work and redoing the whole thing from the beginning. If you arrive at different answers, then you know you must have made a mistake somewhere, and if you arrive at the same answer then you can be more confident that you did not make a mistake. But if the person at the desk next to you thinks to himself “XYZ is reliable, so I’ll just copy down his answer” then having two identical answers cannot increase your confidence that the answer is correct. Please do not agree nor disagree with my identifications unless you know how to, i.e., you know what makes it what. Just withdraw the identification if you're wrong, or don't agree in the first place. Just carelessly agreeing can cause headaches for the iNaturalist identifiers. I must admit that some of my oldest identifications were just carelessly agreeing without me actually knowing what was right or wrong, and this led me to quite a few misidentifications. I also often wanted everything to be brought down to species. I am more conservative. Don't become my old self (he is really annoying at times...). I know spiders can be really difficult to identify, and often specific, generic, or even familial identifications just can't be made without examining the genitalia, a process which can be difficult and one which almost always involves killing the animal. A lot of the time, minor details must be located to confidently identify a particular spider, and some families can include members which can appear identical to another family and with other members appearing identical to a totally different family.

When we try to place an ID on an observation, we are making a best guess based on what we know about the external characteristics of different spiders. In science, specific identifications are almost always made by looking at the shape/structure of the genitalia under a microscope, along with other characteristics that are usually not visible even in high quality macro photos - things like eye spacing, number/location of hairs on the legs, etc. In many cases there are several similar-looking species or even genera that are difficult to separate even with sharp photos. Many species have significant variation in color/size, and many species have never been photographed outside of preserved museum specimens. There are also many undescribed species that look similar to the ones we know about. iNaturalist encourages us to try and figure out exactly what kind of life form we have observed (which is good! curiosity is good!) - but when it comes to small arthropods like spiders, making a confident ID from only photos is often just not possible. This can be frustrating to people who follow popular taxa like birds and butterflies, but it's just a fact of life with many diverse groups of arthropods. So, please accept that it is often not reasonable to place a specific name on a spider just from photographs, and resist the temptation to try and "choose" a species.

Thanks to Justin Williams for the concept and most of the writing on this.

All my life I've been interested in and loving animals, but if it weren't for the cold creeks of NY I don't think I would be. As a young kid perhaps three I would grab toads and laugh when they would pee all over me or I would jump in the small pond in my backyard hoping to finally catch a frog. As I grew up by the age of eight I had caught snakes larger than myself and returned thousands of times with my Grandmother (and occasionally going alone) to my backyard creek to catch salamanders and crawfish. Soon after, my life completely changed and my family and I moved from place to place over the course of a years before I moved into Northeast Florida where I am now and have been for the past four-ish years. (Joined back 10/15/23 with only three observations and no ids) (All of what I said is backed up by photos & stories told by family)

Now, I'm a budding birder taking place in different clubs all over the state and help out with the World Spider Catalog. I'm soon going to undergo verification with the CyperTracker evaluation and will become one of the youngest certified and trusted trackers ever. (Track and Sign knowledge and identification for verified research purposes)

On iNaturalist I've only identified a small amount for my activity, but those 20k identifications actually all took place from the time since late 2023. My knowledge of iNaturalist has expanded and instead of simply reading observations and the comments on them (which I did for most of the time my account has existed) I've now decided to take a place in iNaturalist as a site and add identifications and help out in every way I can!

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Home » Guide » Arthropods (Arthropoda) » Chelicerates (Chelicerata) » Arachnids (Arachnida) » Spiders (Araneae) » True Spiders (Araneomorphae) » Entelegynae » Cobweb Spiders (Theridiidae) » Widow Spiders (Latrodectus) » Southern Black Widow (Latrodectus mactans)
Species Latrodectus mactans - Southern Black Widow
Classification · Other Common Names · Pronunciation · Synonyms and other taxonomic changes · Explanation of Names · Size · Identification · Range · Habitat · Food · Life Cycle · Remarks · See Also · Internet References · Works Cited
Female with egg sac - Latrodectus mactans - female black widow spiderlings - Latrodectus mactans Cool small spider - Latrodectus mactans Southern Black Widow - Latrodectus mactans Pair of black widows - Latrodectus mactans - male - female Spider ID - Latrodectus mactans Southern Black Widow - Latrodectus mactans - female Latrodectus mactans - female
Classification
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Chelicerata (Chelicerates)
Class Arachnida (Arachnids)
Order Araneae (Spiders)
Infraorder Araneomorphae (True Spiders)
No Taxon (Entelegynae)
Family Theridiidae (Cobweb Spiders)
Genus Latrodectus (Widow Spiders)
Species mactans (Southern Black Widow)
Other Common Names
Black Widow - The L. mactans is often considered the original "Black Widow".
“The Hourglass Spider” because of the red hourglass shaped mark on the female’s abdomen.
“The Shoe Button Spider” due to the form of the spider’s jet-black abdomen.
Pronunciation
lat"ro-dek't[schwa]s mac'·tans
Synonyms and other taxonomic changes
See the World Spider Catalog.
Explanation of Names
See the Latrodectus guide page for the etymology of Latrodectus.
Size
Adult Female:
Approximately 8-13 mm (~1/2 inch) in body length.
With legs extended, the female measures about 25-35 mm (1 inch - 1 1/2 inches).

Adult Male:
Approximately half the size of the female, around 4-6 mm (1/4 inch) in body length.
With legs extended, the male measures 12-18 mm (1/2 inch - 2/3 inch).
See this picture for side-by-side view:
Identification
The southern black widow is one of the most common of the native widow spiders. It is the epitome of the classic widow spider, occurring in all the normal widow spider habitats.

Female: The adult female black widow spider has a glossy jet black color all over, including body and legs. The only red marks are the bright red hourglass mark on the underside of the abdomen, and a red spot just behind and above the spinnerets. The hourglass marking consists of two connected red triangles on the underside. Note, however, that the hourglass color may range from yellowish to various shades of orange or red. If the hourglass marking is not connected (e.g. - two distinct, non-touching triangles), it is most likely the northern cousin (L. variolus) of the southern black widow (L. mactans)

Males: Adult males are harmless, is 3-5 mm long with an elongated abdomen. The male’s legs are larger than the female’s and each leg segment is orange brown in the middle and black on the ends. On the sides of the male’s abdomen there are four pairs of red and white stripes. (Net Ref (3))

Immatures: Newly hatched spiderlings are predominately white or yellowish-white, gradually acquiring more black and varying amounts of red and white with each molt. Juveniles of both sexes resemble the male and are harmless. (Net Ref (1))

(Id info from bugguide.net)