Don't have a clue if its an insect or not. Did they get watered while out of town? Check the stem. Scrape with your thumb nail to see if its still green and then plant and water.

Here is a link that might be useful: Propagating Perennials

Haven't had a problem with Meyer's Lemon, but my Lime tree does the same thing. All of the leaves fall off, then it begins to bloom and set fruit. Once the fruit reaches the size of a small marble, they all fall off, almost overnight, then it grows new leaves. I always considered that to be normal, for that weird tree! :Rb

I finally bought one and replanted it immediately. I am treating it as a housplant but I am going to let it live outdoors this summer. It bloomed after I bought it and had too many fruits. Quite a few of them fell off. There are several fruits that are getting bigger and bigger each day---and, it is blooming again. At first, I was not watering it enough, but now it is happy in a sunny window