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Incidentally, if you're interested in seeing some newly hatched Lehmannia valentiana slugs, I'm in the process of posting some pictures on my blog. They're only about 0.5 cm long and so adorable!
You're very welcome. I enjoy discussing these things. And you're exactly right about the slugs: they are basically mothers to one set of eggs and father to another, although it gets tricky if an individual mates more than once: which sperm to use? Decisions, decisions. Haha, I'm interested now to see if you find any more of those eggs. I found my earwig eggs under a bordering-brick, so I guess it's best to literally not leave any stone unturned!
By the way, my earwig mother seems to be moving her eggs deeper and deeper into her burrow. I guess she's tired of my uncovering her home every day and thinks if I can't see the eggs I'll lose interest!
No, I'm pretty sure you identified the slug correctly. The features point towards Lehmannia valentiana. So that's not an issue. Now, I've seen several clutches of L. valentiana eggs in my yard (that's our predominant slug species) and they look nothing like your eggs. From my observation, courting among L. valentiana occurs after investigation by tentacles. It involves trail following (where one slug follows another over some distance), circling (the slugs get into a sort of yin-yang position), and nibbling body mucus. The pair you observed was engaging in tentacle investigation (a precourtship phase) but obviously they didn't form a partnership, as they soon separated. There are evidently criteria involved in selecting a mate, which even scientists debate.
I wouldn't call a slug a "mother" as they're hermaphroditic, meaning they possess both male and female organs, performing both roles. Typically both mating partners donate sperm during copulation and after a few days both lay eggs.
Looking at photos of Leopard Slug eggs, those don't match your eggs either. My inclination is still towards earwigs, but earwigs don't lay that many eggs and the shape is still too elongated. The only certain way to identify the species is to observe what the eggs hatch into. If you spot any more yellow eggs, make a note and check them frequently. Most creatures seem to take at least several days to hatch. But depending on the temperature, the incubation period may be as long as a few months. It's hard to be patient. I know from experience. But it's worth it to solve the mystery. However, in the South the temperature usually doesn't get too cold to halt all invertebrate life.
I think stickiness is a common characteristic of mollusk eggs, but isn't always present in insect eggs.
I'm glad I could be of some assistance. In terms of size, I don't think the clump is too large. 1-1.5 cm is pretty small, around the diameter of the clump of earwig eggs I found. Earwigs can be up to 2.5 cm long, European earwigs around 2 cm long. Also, when I first found my earwig eggs, the mother was hiding in her burrow, not protecting them. She moved the eggs into the burrow later. So an earwig may have laid your eggs in the gutter to move later. Earwigs can overwinter as eggs, and they can lay eggs in either spring or fall.
In terms of the shape, though, I think maybe your eggs are too elongated for an earwig to have laid them. Earwig eggs are oval, but not quite that long, in my understanding. I don't think these are the eggs of a flying insect (they would be upright and more ordered), so it must be a creature on the ground. Do you have any other species of slugs in your yard? Do you have any species of land snail? Some snails can lay quite a clump of eggs.
From my observation, Lehmannia valentiana doesn't show any parental care after laying eggs. I also have this species of slug in my yard, and its eggs are clear, not yellow. I'm not sure why Terrestrial Mollusc Tool lists them as such, because I've seen baby Lehmannia valentiana slugs hatching from whitish eggs. As for your eggs, I've seen a clump of similar-looking ones in my yard, and they belong to a female earwig (Forficula auricularia). Earwig mothers do guard their eggs and move them to shelter.
