Differences in black widow species

Spooddood

Arachnopeon
Joined
May 30, 2019
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I'm just curious if there are any really noticeable, visual differences between Latrodectus hesperus and mactans or if it's more just a matter of the region they're from. I'm having a bit of trouble IDing 2 widows I have. Although I'm pretty sure they're both Hesperus as they were both caught in Utah, I'm still curious to know if there are ways to tell them apart other than location. One is more brown than the other and is more robust. The other is jet black and a on the thinner side, but still plump.
 

NYAN

Arachnoking
Active Member
Joined
Dec 23, 2017
Messages
2,287
I'm just curious if there are any really noticeable, visual differences between Latrodectus hesperus and mactans or if it's more just a matter of the region they're from.
It depends on the region, as there are variations of each species. For the most part, hesperus are jet black except for the hourglass as adults. Mactans, on the other hand, will often have a red dot on the spinnerets. Additionally, the hourglsss shape is different. In mactans the bottom part nearest to the spinnerets is more square. Hesperus is more triangular, and will occasionally be broken. It takes more experience to tell slings and juveniles apart, so I’ll leave it at that.

Although I'm pretty sure they're both Hesperus as they were both caught in Utah, I'm still curious to know if there are ways to tell them apart other than location.
Mactans is not found west of Texas.

One is more brown than the other and is more robust. The other is jet black and a on the thinner side, but still plump.
The brown one is likely immature.
 
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