Sawfly larvae resemble caterpillars but they have more than 5 pairs of prolegs on the abdomen. Adults are actually wasps. A common sawfly that may be found attacking hibiscus is the hibiscus sawfly. The adult is small and black with a red spot and smoky wings. The larvae are pale green with a dark head. They like to feed in groups and many may be found together feeding on lower surface of the leaves. Eventually, they may eat the entire leaf, leaving the mid-vein. Heavy infestations may cause complete defoliation. Hollyhock sawfly is another common sawfly in the garden.
Light infestations may be controlled by manually removing and destroying the sawflies. Heavy infestations of young larvae may be sprayed with horticultural oil. Even though sawflies look like caterpillars, they aren't. Bt (Bacillus thuringiensis) will not control sawflies. (Bt is a microbial insecticide that controls caterpillars).