Question About Latrodectus Hesperus (Western Black Widow) Spiderling feeding not growing

[Khaos Weaver]

So I have around 40 Western Black Widows that hatched around March 20th. I have numbered them while babies because it is just easier that way so my question is regarding one of my spiderlings #12. I have been feeding all of them flightless fruit flies, and all but one have been molting and growing. Number #12 made its first kill after being placed in its own container. I added a small cotton ball at the bottom with water for all my spiderlings to ensure they had a water source and a bit of humidity for molting. The cups have cross-ventilation holes in them. A couple of the spiderlings, including #12, I had to pre-kill the fly, but it didn't appear to bother them. They quickly started webbing it and feeding. For #12, I noticed it wasn't showing interest, so I removed the food, thinking perhaps it was about to molt. After a few days, it still had not molted. I decided to place a pre-killed fly in its web, and it quickly fed on it. I have been watching for it to molt, but it has still not changed in size nor molted. It still feeds. I have fed it and seen it latched to the prey, feeding, but it has not grown. It looks the same as when it hatched. Does anyone know what is happening here? Is there anything I can do? It doesn't seem weak or sick. It just isn't growing. If it is feeding, I don't understand how this would be possible. I'm really confused. has anyone else experienced this? Any help or thoughts would be appreciated!

 

[The Snark]

Sounds like a case of natural selection.
"principle by which each slight variation [of a trait], if useful, is preserved"

 

[Khaos Weaver]

Sounds like a case of natural selection.
"principle by which each slight variation [of a trait], if useful, is preserved"

You’re probably correct. My bathroom is a eco system of natural selection. I caught this first group shortly after they hatched in my bathroom. The mother sadly died three days before they emerged. I came into the bathroom to find a highway of web going straight up from the main web to the lightbulb above, which was covered in baby widows. I left them to their business while I went in search of containers to collect them in. When I had those and returned to the bathroom, the number of spiderlings on the lightbulb was a lot less, and it appeared a line of them was making their way down. That’s when I saw the outline of what at first appeared to be a large hairy spider on the bulb. At first, I was like, “ WTF is that!? The light from beneath it and its hair made it look like a much larger spider than it was. It was a jumping spider that apparently had made its home in the light fixture. I watched, and it was catching the spiderlings. I don't know if it was eating them or just taking them out. It took me about a week to lure it into a large container with a mealworm, but not before we did a few staring contests, and it faked me out with a few jump scares. The first time it jump-scared me was while I was looking at it looking at me when suddenly it leaped at me, and I yelped and jumped back and spent a few good minutes dumbly searching the ground for it. When I glanced up, it was sitting on the mirrored medicine cabinet, perched on the corner of it, with its attention looking downward at where I was. I could just imagine it laughing at me. Moments after looking up at it, the fluffy trickster seemed to realize I had noticed it and turned back towards the light and scurried away to hide. I eventually convinced it to move into a container I set up for it and promised I’d get it a nice luxury condo and feed it regularly. I named it Widow Reaper. It is a fun little spider it likes to watch my computer screen when I'm doing stuff and chase my finger around. I keep meaning to upload images of it, but I have been busy with feeding the babies I caught and catching new ones I find. I attached some with this reply.

 

[The Snark]

Some kind of Salticid. They can chow down on spiderlings like a king cobra mows through a pond of tadpoles. They always lay down a life line wherever they go. The jump is a survival reflex as well as their hunting method. They reel themselves back up the life line or lower themselves down - any port in the storm thing.