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agree with Organoman, leaf miners.

"leaf miner" in english.........a bug that eats leaf tissue. Bacillus thuringiensis is a safe and effective organic biological control.

it is a "leaf miner". 🐛 What is a Leaf Miner? A leaf miner is the larva of various insect species that live inside plant leaves and feed on their tissue. Here's a breakdown: Larvae of different insects: Most commonly moths (Lepidoptera), sawflies (Symphyta), flies (Diptera), or beetles (Coleoptera). Life inside the leaf: The larva burrows between the layers of the leaf, creating characteristic "tunnels" or "blotches" that appear as pale lines or spots on the leaf surface. Damage to plants: While they rarely kill the plant, they can significantly reduce its aesthetic value and weaken it, especially if infestations are repeated. 🌱 How to Recognize an Infestation Winding pale lines on leaves Blotches or spots caused by multiple larvae feeding in one leaf Frass (larval droppings) visible inside the leaf How to Control Leaf Miners Organic methods: Use products like spinosad, which must be ingested by the larvae Mechanical methods: Remove and destroy affected leaves Biological control: Introduce natural predators Trap crops: Plants like spinach or lamb’s quarters can attract leaf miners and protect more valuable crops

It's called Phyllocnistis citrella, it's a parasite, it is usually called a "minador de hojas" here in Spain