The Schizophora are a

section Section, Sectioning, or Sectioned may refer to: Arts, entertainment and media * Section (music), a complete, but not independent, musical idea * Section (typography), a subdivision, especially of a chapter, in books and documents ** Section sig ...

of true flies containing 78 families, which are collectively referred to as muscoids, although technically the term "muscoid" should be limited to flies in the superfamily

Muscoidea Muscoidea is a superfamily of flies in the subsection Calyptratae. Muscoidea, with approximately 7000 described species, is nearly 5% of the known species level diversity of the Diptera, the true flies. Most muscoid flies are saprophagous, copr ...

; this is an example of informal, historical usage persisting in the vernacular. The section is divided into two subsections, the Acalyptratae and

Calyptratae Calyptratae is a subsection of Schizophora in the insect order Diptera, commonly referred to as the calyptrate muscoids (or simply calyptrates). It consists of those flies which possess a calypter that covers the halteres, among which are some ...

, which are commonly referred to as acalyptrate muscoids and calyptrate muscoids, respectively. The defining feature of the Schizophora is the presence of a special structure used to help the emerging adult fly break free of the puparium; this structure is an inflatable membranous sac called the

ptilinum The ptilinum is an eversible pouch on the head, above the base of the Antenna (biology), antenna in Schizophora, schizophoran Diptera, flies (a section (biology), section of Muscomorpha, muscomorphan and Cyclorrhapha, cyclorrhaphan flies). It is ...

that protrudes from the face, above the antennae. The inflation of the ptilinum (using fluid

hemolymph Hemolymph, or haemolymph, is a fluid, similar to the blood in invertebrates, that circulates in the inside of the arthropod's body, remaining in direct contact with the animal's tissues. It is composed of a fluid plasma in which hemolymph c ...

rather than air) creates pressure along the line of weakness in the puparium, which then bursts open along the seam to allow the adult to escape. When the adult emerges, the fluid is withdrawn, the ptilinum collapses, and the membrane retracts entirely back inside the head. The large, inverted, U-shaped suture in the face through which it came, however, is still quite visible, and the name "Schizophora" ("split-bearers") is derived from this ptilinal or frontal suture. The term was first used by Eduard Becher. In contrast to eggs of other arthropods, most insect eggs are drought-resistant, because inside the maternal

chorion The chorion is the outermost fetal membrane around the embryo in mammals, birds and reptiles (amniotes). It is also present around the embryo of other animals, like insects and molluscs. Structure In humans and other therian mammals, the cho ...

, two additional membranes develop from embryonic tissue, the

amnion The amnion (: amnions or amnia) is a membrane that closely covers human and various other embryos when they first form. It fills with amniotic fluid, which causes the amnion to expand and become the amniotic sac that provides a protective envir ...

and the

serosa The serous membrane (or serosa) is a smooth epithelial membrane of mesothelium lining the contents and inner walls of body cavities, which secrete serous fluid to allow lubricated sliding movements between opposing surfaces. The serous mem ...

. This serosa secretes a

cuticle A cuticle (), or cuticula, is any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticle" are non- homologous, differing in their origin, structu ...

rich in

chitin Chitin (carbon, C8hydrogen, H13oxygen, O5nitrogen, N)n ( ) is a long-chain polymer of N-Acetylglucosamine, ''N''-acetylglucosamine, an amide derivative of glucose. Chitin is the second most abundant polysaccharide in nature (behind only cell ...

that protects the embryo against desiccation. In the Schizophora, however, the serosa does not develop, but these flies lay their eggs in damp places, such as rotting organic matter. The absence of schizophoran flies from

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...

rocks implies that they likely rapidly diversified during the

Cenozoic The Cenozoic Era ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterized by the dominance of mammals, insects, birds and angiosperms (flowering plants). It is the latest of three g ...

, with the first appearance of the group during the early

Paleogene The Paleogene Period ( ; also spelled Palaeogene or Palæogene) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period Ma (million years ago) to the beginning of the Neogene Period Ma. It is the fir ...

, around 53 million years ago, with it being estimated that they split off from other flies around 66-65 million years ago.

References

External links

Tree of Life SchizophoraJoyce Laing on the ptilinum pdf
{{Taxonbar, from=Q1102504 Protostome unranked clades