Perhaps citrus leafminer?

See this page http://www.ipm.ucdavis.edu/PMG/GARDEN/FRUIT/citrus.html

Here is a link that might be useful: citrus

Jean is correct, Citrus Leafminer. This mainly cosmetic disease is caused by a tiny little moth that lays its eggs on the undersides of citrus leaves. The larvae hatch and tunnel through the leaf, eventually exiting as they turn into moths. Too late to do anything this season, but next year, about 2 weeks prior to damaging appearing in your area (for you, I would suggest early June), you can apply Bayer Advanced Fruit & Vegetable Insect Control which will protect your plants for 6 months. Or, if you prefer something organic, you can start spraying at about the same time and then every 3 weeks through about October with a combination of Spinosad and a hort oil (such as Volck or Neem). Just remember not to use a hort oil if temps will exceed 85 degrees, as that can burn the leaves. Leave the curled leaves on the plant. Although they may look a little gnarled, your your tree needs those leaves to continue to conduct photosynthesis and provide energy to the tree.

Patty S.