Answer: A number of different beetles will "skeletonize" hollyhock leaves--they chew away the soft parts of the leaves, leaving behind the veins and creating a lacy look. Japanese beetles and rose chafers are two common pests; however, both these pests lay their eggs in the soil.
It's hard to know if the "fly-like" bugs you've seen are the culprits. For example, another group of pests are moth larvae; have you seen any small caterpillars on the backs of the leaves?
In any case, your best bet would be to go outdoors in the cool of early morning, and knock any pests you see chewing on the leaves into a can of soapy water. (Insects move more slowly at cooler temps.) At the same time, squish any eggs you see on the backs of the leaves. You might also try a neem-based repellent, such as Neem-Away (sold by Gardens Alive, 5100 Schenley Rd., Lawrenceburg IN 47025; 812/537-8650). If you find that caterpillars are the culprits, then the biological control B.t. would be a good choice. Both of these are considered organic controls.
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