Symphyta

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 families 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 ostentatus 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 continent. Other than the families discussed here, a number of fossil families have been described, most all from 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 confused 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 superfamily 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 orthandrous in the Macroxyelinae and strophandrous in the Xyelinae. ~All members of this suborder are phytophagous except for the family Orussidae which is parasitic on other wood-boring insects. Host plants and habits are various. Many larvae are external feeders on the foliage of the host, but others are leaf miners, gall formers on twigs, petioles, leaves, or buds, leaf-edge rollers, stem borers, wood borers, or petiole miners. Because of their plant feeding habits, many sawflies are pests of ornamental plants, agricultural crops, or forest stands. Their occurrence is normally local, but outbreaks in forests may be extensive, covering many thousands of acres and resulting in considerable growth loss or death of trees. Appearance in epidemic proportions is commonly sporadic, suddenly appearing for a year or more then practically disappearing for several years, probably being kept under control by their natural parasite-predator-disease complex. Some of the most destructive species are aliens which were accidentally introduced from abroad and found a vacuum for development without natural enemies. Many parasites have been introduced to help combat these pests. Some of the more important sawflies are those that feed on timber species, roses, apples, pears, peaches, and wheat and other grain crops. On the other hand, a few sawflies have been used beneficially, or at least have been attempted for use in the biological control of weeds. One species, Ucona acaenae Smith (=Antholcus varinervis of authors), was introduced into New Zealand from Chile in the early 1930's to help control the spread of Acaena. This attempt was only partially successful. Another species, Priophorus morio (Lepeletier), was released in Hawaii from the western United States to help control the spread of Rubus on the islands, but this attempt failed. ~The life cycle of many sawflies follows a similar pattern, though with many variations. Adults of most species fly in spring and early summer and are very short-lived. It is difficult to keep individual adults alive in captivity for much more than a few days although the actual flight of a species may extend over several weeks or months. Some adults may not feed but some may feed on moisture, nectar and pollen of flowers, leaf pubescence, or other insects. The most productive areas for collecting are in vegetation on edges of rivers or streams, marshes, open and scrubby woodland, or undisturbed meadows. The catkins of willows and alders are especially productive for many groups. Oviposition is in the foliage, stems, twigs, or wood, and the eggs are most always inserted in the plant tissue though some Pamphiliidae may glue their eggs to the leaf surface. Larval feeding time varies, but usually lasts about two weeks. Many larvae, especially Diprionidae, feed gregariously at first but later disperse to other parts of the host. After feeding is completed the larva molts into a non-feeding stage called the prepupa or resting stage. The prepupa normally leaves the host in search of a site for pupation. This may be in a cell in the ground or litter, in a papery cocoon in the ground, in some other substance such as wood, stems of the host or nearby plants, or fruits of other plants. The prepupal stage differs morphologically from the feeding stages, especially in the shape of the mandibles and sometimes color pattern. Some larvae with spines loose these in the final molt. If there is a single generation, the prepupa will remain in its cocoon or cell the rest of the summer and pupate the following spring. However, depending on the species, latitude, or diapause requirements, there may be several generations a year, or it may take several years to complete the cycle. ~The following references are to general articles on the Symphyta. Some, such as Maxwell, 1955, in morphology, pertain to many species and the reference is not repeated under each species. Under some species, such as Pristiphora erichsonii (Hartig), a listing of all biological references would take many more pages, and the references are selected or pertain to some recent synopsis which contains a good bibliography. Some of the new distribution records, hosts, and taxonomic changes are taken from unpublished notes. Only those taxonomic changes cited as being new have not before appeared in the literature. ~I am indebted to several colleagues for reviewing parts of this section and or providing some of the information contained herein: H. E. Milliron, formerly with the Biosystematics Research Institute, Agriculture Canada, Ottawa and other authorities of the Institute for allowing study of their sawfly collection; H. R. Wong, Northern Forest Research Centre, Canadian Forestry Service Edmonton, Alberta, Canada; and H. Greenbaum, Department of Entomology, University of Arkansas Fayetteville.

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 families 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 ostentatus 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 continent. Other than the families discussed here, a number of fossil families have been described, most all from 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 confused 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 superfamily 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 orthandrous in the Macroxyelinae and strophandrous in the Xyelinae. ~All members of this suborder are phytophagous except for the family Orussidae which is parasitic on other wood-boring insects. Host plants and habits are various. Many larvae are external feeders on the foliage of the host, but others are leaf miners, gall formers on twigs, petioles, leaves, or buds, leaf-edge rollers, stem borers, wood borers, or petiole miners. Because of their plant feeding habits, many sawflies are pests of ornamental plants, agricultural crops, or forest stands. Their occurrence is normally local, but outbreaks in forests may be extensive, covering many thousands of acres and resulting in considerable growth loss or death of trees. Appearance in epidemic proportions is commonly sporadic, suddenly appearing for a year or more then practically disappearing for several years, probably being kept under control by their natural parasite-predator-disease complex. Some of the most destructive species are aliens which were accidentally introduced from abroad and found a vacuum for development without natural enemies. Many parasites have been introduced to help combat these pests. Some of the more important sawflies are those that feed on timber species, roses, apples, pears, peaches, and wheat and other grain crops. On the other hand, a few sawflies have been used beneficially, or at least have been attempted for use in the biological control of weeds. One species, Ucona acaenae Smith (=Antholcus varinervis of authors), was introduced into New Zealand from Chile in the early 1930's to help control the spread of Acaena. This attempt was only partially successful. Another species, Priophorus morio (Lepeletier), was released in Hawaii from the western United States to help control the spread of Rubus on the islands, but this attempt failed. ~The life cycle of many sawflies follows a similar pattern, though with many variations. Adults of most species fly in spring and early summer and are very short-lived. It is difficult to keep individual adults alive in captivity for much more than a few days although the actual flight of a species may extend over several weeks or months. Some adults may not feed but some may feed on moisture, nectar and pollen of flowers, leaf pubescence, or other insects. The most productive areas for collecting are in vegetation on edges of rivers or streams, marshes, open and scrubby woodland, or undisturbed meadows. The catkins of willows and alders are especially productive for many groups. Oviposition is in the foliage, stems, twigs, or wood, and the eggs are most always inserted in the plant tissue though some Pamphiliidae may glue their eggs to the leaf surface. Larval feeding time varies, but usually lasts about two weeks. Many larvae, especially Diprionidae, feed gregariously at first but later disperse to other parts of the host. After feeding is completed the larva molts into a non-feeding stage called the prepupa or resting stage. The prepupa normally leaves the host in search of a site for pupation. This may be in a cell in the ground or litter, in a papery cocoon in the ground, in some other substance such as wood, stems of the host or nearby plants, or fruits of other plants. The prepupal stage differs morphologically from the feeding stages, especially in the shape of the mandibles and sometimes color pattern. Some larvae with spines loose these in the final molt. If there is a single generation, the prepupa will remain in its cocoon or cell the rest of the summer and pupate the following spring. However, depending on the species, latitude, or diapause requirements, there may be several generations a year, or it may take several years to complete the cycle. ~The following references are to general articles on the Symphyta. Some, such as Maxwell, 1955, in morphology, pertain to many species and the reference is not repeated under each species. Under some species, such as Pristiphora erichsonii (Hartig), a listing of all biological references would take many more pages, and the references are selected or pertain to some recent synopsis which contains a good bibliography. Some of the new distribution records, hosts, and taxonomic changes are taken from unpublished notes. Only those taxonomic changes cited as being new have not before appeared in the literature. ~I am indebted to several colleagues for reviewing parts of this section and or providing some of the information contained herein: H. E. Milliron, formerly with the Biosystematics Research Institute, Agriculture Canada, Ottawa and other authorities of the Institute for allowing study of their sawfly collection; H. R. Wong, Northern Forest Research Centre, Canadian Forestry Service Edmonton, Alberta, Canada; and H. Greenbaum, Department of Entomology, University of Arkansas Fayetteville.