Towards a functional understanding of the cyclorrhaphan larval head (Diptera, Cyclorrhapha)

The larval stage is thought to play a significant role in radiations of Diptera (Insecta), but for the Cyclorrhapha (Diptera), a well-supported and diversified clade, evaluating larval roles is hindered by low taxon sampling, unresolved morphology and presumed similarity. This paper reviews investigations of the cyclorrhaphan larval head based on wider taxon sampling and functional assessment. It examines whether misunderstandings and superficial levels of analysis may have overestimated these difficulties. Functional assessment is a technique for investigating larvae and begins the process of making larvae better known as living organisms. For instance, functional assessments of larvae in the lower Cyclorrhapha helps resolve structures including the antenna and mandible whose homology is unclear. The levels of sclerotisation, alignment and fusion of head structures can predict feeding mechanisms and help turn the enigmatic cyclorrhaphan larval head into an analysable component.