Not all things tubular are caterpillars, just like not all caterpillars are tubular. The Dogwood Sawfly is actually in the wasp family. It is completely unrelated to butterflies and moths, but its larvae look just like caterpillars. Even though it is part of the wasp family, the larva does not sting. The number of prolegs is one feature that is helpful in differentiating between real caterpillars and sawfly larvae. Caterpillars have legs at the head and no more than 5 pairs of prolegs by the rear end. Sawfly larvae have at least 6 pairs of prolegs and they run the whole length of the body.
This species has a few appearances depending on where it is in this life stage. A colorful one has a black and white banded pattern on the top and a yellow belly. The white bands alternate: a long one, then short one on each segment. A white dorsal stripe runs down the 'spine'. Another look is powdery white and waxy. Sometimes they are mostly white or yellow with faint black dots forming on the 'back'. The Dogwood Sawfly larva feeds on dogwood leaves late in the season, and at dusk or nighttime. During the day, it curls up and hides under leaves. It may be found in a group. It eats entire leaves, and removing groups from a tree while they are still small can prevent spotty and unattractive defoliation. Very young trees may suffer from severe defoliation, but mature trees can handle the nibbling.
Sawflies look like plump flies and do not sting. The female uses her ovipositor to cut or saw into the edge of a dogwood leaf or stem. She then inserts her fertilized eggs into the slit. As soon as the eggs hatch, the larvae can begin consuming the leaves around them. While they feed, the sawfly larvae may become victims to wasps and hornets, where they are taken back to nests to feed those young larvae. Dogwood sawfly larvae that survive will overwinter and pupate in the spring, emerging as adult Sawflies later in the year.
The map above showcases (in blue) the states and territories of North America where the Dogwood Sawfly Larva may be found (but is not limited to). This sort of data can be useful in seeing concentrations of a particular species over the continent as well as revealing possible migratory patterns over a species' given lifespan. Some species are naturally confined by environment, weather, mating habits, food resources and the like while others see widespread expansion across most, or all, of North America.*NOTE: States/Territories shown above are a general indicator of areas inhabited by the Dogwood Sawfly Larva. Insects generally go where they please, typically driven by diet, environmental changes, and / or mating habits.