Suborder SYMPHYTA 



By David R. Smith 



The suborder Symphyta, commonly known as sawflies and horntails, has also been recorded in 

 the early literature under the names Chalastogastra, Sessiliventria, or Phyllophaga and 

 Xylophaga. The suborder includes about 10,000 world species grouped into about 1,000 genera 

 and 12 families. Representatives are found on all continents except for Antarctica, and they are 

 also absent on many of the more isolated islands of the world such as Hawaii and many other 

 Pacific islands. The most northern record is that for Pachynematus parvilabris (Thomson) on 

 Ward Hunt Island in Canada, 83" 05' N., and several species are found as far south as Tierra del 

 Fuego. The North American fauna consists of around 1,000 species in 10 families. The two fami- 

 lies that have no living representatives in North America are the Megalodontidae and 

 Blasticotomidae,both of which are Palearctic, though the Blasticotomidae is represented in North 

 America by the fossil species Paremphytus ostentus Brues from the Miocene of Florissant, 

 Colorado. The Blasticotomidae contains only several species, very secretive and rarely found, 

 the larvae of which bore in the stems of ferns. Living forms may yet be discovered on this con 

 tinent. Other than the families discussed here, a number of fossil families have been described, 

 most all fi im the Old World. These are Anaxyelidae, Gigasiricidae, Karatavitidae, Myrmiciidae, 

 Parapamphiliidae, Pararchexyelidae, Paroryssidae, Pseudosiricidae, Sepulcidae, Xyelotomidae, 

 and Xyelydidae. 



The common name sawfly, applied to members of most families, is derived from their flylike 

 appearance and the sawlike female ovipositor which is used to cut open plant tissue for insertion 

 of eggs. The name horntail is usually applied to members of the family Siricidae, the females of 

 which have a long slender ovipositor. Adults of the suborder may be distinguished from other 

 Hymenoptera by the abdomen which is broadly joined to the thorax, the trochanters which are 

 always two-segmented and the hindwing which usually has three closed basal cells. The larvae of 

 most sawflies are entirely different from other Hymenoptera larvae and are most often con- 

 fused with those of Lepidoptera, though sawfly larvae lack crochets on the prolegs, have only 

 one pair of ocelli, and normally have more than five pairs of prolegs. Some larvae, especially 

 those modified for an internal existence, resemble the grublike larvae of other Hymenoptera but 

 normally have a projection at the apex of the abdomen and vestiges of thoracic legs. 



The higher classification of the Symphyta in most universal use at present is that proposed by 

 Ross (1937) and Benson (1938). The suborder is divided into two major series, the Orthandria 

 and Strophandria basically separated by the male genitalia which remains normal in the former 

 but is turned 180° prior to eclosion in the latter. The Strophandria is expressed as the super- 

 family Tenthredinoidea. The Orthandria have been further divided on the basis of characters of 

 the mesosternum and head capsule into three superfamilies, the Megalodontoidea, Siricoidea, 

 and Cephoidea. Some authors have recognized the superfamily Xyeloidea including only the 

 family Xyelidae. This has some merit, as both positions of male genitalia are found, the orthan- 



