The citrus leafminer is an insect of scientific name Phyllocnistis citrella that in its larvaria phase lives as parasitic under cuticle of the leaves and tender shoots of the citrus trees of any species, feeding on the vegetal cells to which empty perforating its cytoplasmic membrane and sucking its liquid content. Exceptionally, in the absence of leaves, also it can parasitize the green fruits.
A day about 7 years ago taking a walk by my garden a tiny small bird, Phylloscopus collybita, drew attention to me, that jumped of small branch in small branch on an old lemon tree and watched underneath each leaf. Of as much as soon as it found a small worm, it squashed a little with its smallest tip of insectivore and swallowed it as if outside delicious food. The bird overflowed joy and realised a species of dance with small jumps and movements of the tail whenever a worm swallowed. I was observing it during a good short while and it did not seem to bother my presence, so engrossed was with its big spread. When it was sated of worms went flying until the drinking trough of geeses, drank several times and it disappeared. Suspecting that it had been fed on leafminer larvae, I look under the leaves where the bird had been and indeed all cuticle had broken and the larva had disappeared.