Symphyta

Symphyta is a suborder of insects within Hymenoptera that includes the sawflies and their close relatives, such as horntails. They are distinguished from the Apocrita (ants, bees, and stinging wasps) by a broadly joined abdomen, lacking the narrow constriction or "waist" found in the other lineage. Adults generally have chewing mouthparts and range from small to medium in size. The larvae resemble caterpillars, with numerous prolegs on most of the abdominal segments, and most feed on plants—leaves, needles, or stems. Some species bore into wood, particularly in the family Siricidae (horntails), where larvae develop in dead or decaying wood.

Reproduction involves females laying eggs with a saw-like ovipositor; the term “sawflies” derives from this tool. Eggs hatch into larvae, which molt through several instars before entering a pupal stage and emerging as adults. Like other Hymenoptera, Symphyta undergo complete metamorphosis.

Systematics: Symphyta comprises several superfamilies, including Cephoidea, Pamphilioidea, Tenthredinoidea, Xiphydrioidea, and Siricoidea. The group is considered paraphyletic with respect to the Apocrita, the lineage that gives rise to most stinging wasps, bees, and ants. Taxonomic relationships within Symphyta are subject to revision as phylogenetic studies refine family-level classifications.

Ecology and importance: Most Symphyta larvae are herbivores feeding on a variety of woody and herbaceous plants. Some species can become forest or orchard pests by causing defoliation or damage, while others play roles in natural plant–insect interactions and nutrient cycling. They occur worldwide in a broad range of habitats.