Orthorrhapha

Orthorrhapha is an informal grouping of flies within the order Diptera. This classification is based on the structure of the larval mouthparts, specifically the presence of unpaired, rod-like, internal mouth hooks. These mouth hooks are used for scraping food and for movement within their substrate. This contrasts with the other major informal group of flies, the Cyclorrhapha, which have more complex larval mouthparts with paired, heavily sclerotized structures. Orthorrhaphous larvae are often described as vermiform or maggot-like, though the degree of sclerotization of the mouth hooks can vary.

The Orthorrhapha group includes a wide diversity of families, such as the Tipulidae (crane flies), Culicidae (mosquitoes), Chironomidae (midges), Simuliidae (black flies), and Tabanidae (horse flies), among many others. These families exhibit a vast range of ecological roles and life cycles. For instance, crane fly larvae are often found in moist soil or aquatic environments, feeding on decaying organic matter, while mosquito larvae are aquatic and filter feeders.

It is important to note that Orthorrhapha is not a formal taxonomic rank like order or family. It is a descriptive term based on a specific morphological feature of the larvae. Modern phylogenetic studies, often based on molecular data, have shown that the traditional Orthorrhapha grouping is paraphyletic, meaning it does not include all descendants of a common ancestor. However, the term remains useful for descriptive purposes, particularly when discussing larval morphology and evolution within the Diptera. The distinction between Orthorrhapha and Cyclorrhapha has been a foundational concept in entomological studies of flies for a considerable time.