Sawfly

-like ovipositor for which the group is named The suborder name "Symphyta" derives from the Greek word , meaning 'grown together', referring to the group's distinctive lack of a wasp waist between prostomium and peristomium. Its common name, "sawfly", derives from the saw-like ovipositor that is used for egg-laying, in which a female makes a slit in either a stem or plant leaf to deposit the eggs. Sawflies are also known as "wood-wasps". ==Phylogeny==

established the suborder Symphyta. In his original description of Hymenoptera in 1863, German zoologist Carl Gerstaecker divided them into three groups, Hymenoptera aculeata, Hymenoptera apocrita and Hymenoptera phytophaga. However, four years later in 1867, he described just two groups, H. apocrita syn. genuina and H. symphyta syn. phytophaga. The Symphyta have therefore traditionally been considered, alongside the Apocrita, to form one of two suborders of Hymenoptera. Symphyta are the more primitive group, with comparatively complete venation, larvae that are largely phytophagous, and without a "wasp-waist", a symplesiomorphic feature. Together, the Symphyta make up less than 10% of hymenopteran species. While the terms sawfly and Symphyta have been used synonymously, the Symphyta have also been divided into three groups, true sawflies (phyllophaga), woodwasps or xylophaga (Siricidae), and Orussidae. The three groupings have been distinguished by the true sawflies' ventral serrated or saw-like ovipositor for sawing holes in vegetation to deposit eggs, while the woodwasp ovipositor penetrates wood and the Orussidae behave as external parasitoids of wood-boring beetles. The woodwasps themselves are a paraphyletic ancestral grade. Despite these limitations, the terms have utility and are common in the literature. Cladistic methods and molecular phylogenetics are improving the understanding of relationships between the superfamilies, resulting in revisions at the level of superfamily and family. The Symphyta are the most primitive (basal) taxa within the Hymenoptera (some going back 250 million years), and one of the taxa within the Symphyta gave rise to the monophyletic suborder Apocrita (wasps, bees, and ants). One fossil, Archexyela ipswichensis from Queensland is between 205.6 and 221.5million years of age, making it among the oldest of all sawfly fossils. More Xyelid fossils have been discovered from the Middle Jurassic and the Cretaceous, but the family was less diverse then than during the Mesozoic and Tertiary. The subfamily Xyelinae were plentiful during these time periods, in which Tertiary faunas were dominated by the tribe Xyelini; these are indicative of a humid and warm climate. The cladogram is based on Schulmeister 2003. }} Taxonomy : Syntexis libocedrii There are approximately 8,000 species of sawfly in more than 800 genera, although new species continue to be discovered. However, earlier studies indicated that 10,000 species grouped into about 1,000 genera were known. Early phylogenies such as that of Alexandr Rasnitsyn, based on morphology and behaviour, identified nine clades which did not reflect the historical superfamilies. Such classifications were replaced by those using molecular methods, starting with Dowton and Austin (1994). As of 2013, the Symphyta are treated as nine superfamilies (one extinct) and 25 families. Most sawflies belong to the Tenthredinoidea superfamily, with about 7,000 species worldwide. Tenthredinoidea has six families, of which Tenthredinidae is by far the largest with some 5,500 species. Extinct taxa are indicated by a dagger (). Superfamilies and families • Superfamily Anaxyeloidea • Family Anaxyelidae (1 species) and 12 genera • Superfamily Cephoidea (1 and 1 family) • Family Cephidae (21 genera, 160 spp. and 3 genera • Superfamily Karatavitoidea (1 family) • Family Karatavitidae (7 genera) • Superfamily Orussoidea (1 and 1 family) • Family Orussidae (16 genera, 82 spp.) and 3 genera • Superfamily Pamphilioidea (2 and 1 families) (syn. Megalodontoidea) • Family Megalodontesidae (1 genera, 42 spp.) and 1 genus • Family Pamphiliidae (10 genera, 291 spp.) and 3 genera • Superfamily Siricoidea (2 and 5 families) • Family Siricidae (11 genera, 111 spp.) and 9 genera • Superfamily Tenthredinoidea (6 and 2 families) • Family Argidae (58 genera, 897 spp.) and 1 genus • Family Blasticotomidae (2 genera, 12 spp.) and 1 genus • Family Cimbicidae (16 genera, 182 spp.) and 6 genera • Family Diprionidae (11 genera, 136 spp.) and 2 genera • Family Pergidae (60 genera, 442 spp.) • Family Tenthredinidae (400 genera, 5,500 spp.) and 14 genera • Superfamily Xiphydrioidea • Family Xiphydriidae (28 genera, 146 spp.) • Superfamily Xyeloidea • Family Xyelidae (5 genera, 63 spp.) and 47 genera ==Description==

Many species of sawfly have retained their ancestral attributes throughout time, specifically their plant-eating habits, wing veins and the unmodified abdomen, where the first two segments appear like the succeeding segments. The absence of the narrow wasp waist distinguishes sawflies from other members of hymenoptera, although some are Batesian mimics with similar to wasps and bees, and the ovipositor can be mistaken for a stinger. The smaller species only reach lengths of . Heads of sawflies vary in size, shape and sturdiness, as well as the positions of the eyes and antennae. They are characterised in four head types: open head, maxapontal head, closed head and genapontal head. The open head is simplistic, whereas all the other heads are derived. The head is also hypognathous, meaning that the lower mouthparts are directed downwards. When in use, the mouthparts may be directed forwards, but this is only caused when the sawfly swings its entire head forward in a pendulum motion. Unlike most primitive insects, the sutures (rigid joints between two or more hard elements on an organism) and sclerites (hardened body parts) are obsolescent or absent. The clypeus (a sclerite that makes up an insects "face") is not divided into a pre- and postclypeus, but rather separated from the front. The antennal sclerites are fused with the surrounding head capsule, but these are sometimes separated by a suture. The number of segments in the antennae vary from six in the Accorduleceridae to 30 or more in the Pamphiliidae. The compound eyes are large with a number of facets, and there are three ocelli between the dorsal portions of the compound eyes. The tentorium comprises the whole inner skeleton of the head. Three segments make up the thorax: the mesothorax, metathorax and prothorax, as well as the exoskeletal plates that connect with these segments. The legs have spurs on their fourth segments, the tibiae. Sawflies have two pairs of translucent wings. The fore and hind wings are locked together with hooks. Parallel development in sawfly wings is most frequent in the anal veins. In all sawflies, 2A and 3A tend to fuse with the first anal vein. This occurs in several families including Argidae, Diprionidae and Cimbicidae. ally coloured caterpillar-like larva of Abia sericea The larvae of sawflies are easily mistaken for lepidopteran larvae (caterpillars). However, several morphological differences can distinguish the two: while both larvae share three pairs of thoracic legs and an apical pair of abdominal prolegs, lepidopteran caterpillars have four pairs of prolegs on abdominal segments 3–6 while sawfly larvae have five pairs of prolegs located on abdominal segments 2–6; crochets are present on lepidopteran larvae, whereas on sawfly larvae they are not; the prolegs of both larvae gradually disappear by the time they burrow into the ground, therefore making it difficult to distinguish the two; and sawfly larvae only have a single pair of minute eyes, whereas lepidopteran larvae have four to six eyes on each side of the head. Sawfly larvae behave like lepidopteran larvae, walking about and eating foliage. Some groups have larvae that are eyeless and almost legless; these larvae make tunnels in plant tissues including wood. Many species of sawfly larvae are strikingly coloured, exhibiting colour combinations such as black and white while others are black and yellow. This is a warning colouration because some larvae can secrete irritating fluids from glands located on their undersides. == Distribution ==

Sawflies are widely distributed throughout the world. The largest family, the Tenthredinidae, with some 5,000 species, are found on all continents except Antarctica, though they are most abundant and diverse in the temperate regions of the northern hemisphere; they are absent from New Zealand and there are few of them in Australia. The next largest family, the Argidae, with some 800 species, is also worldwide, but is most common in the tropics, especially in Africa, where they feed on woody and herbaceous angiosperms. Of the other families, the Blasticotomidae and Megalodontesidae are Palearctic; the Xyelidae, Pamphilidae, Diprionidae, Cimbicidae, and Cephidae are Holarctic, while the Siricidae are mainly Holarctic with some tropical species. The parasitic Orussidae are found worldwide, mostly in tropical and subtropical regions. The wood-boring Xiphydriidae are worldwide, but most species live in the subtropical parts of Asia. ==Behaviour and ecology==

(Hartigia trimaculata) larva in a rose stem Sawflies are mostly herbivores, feeding on plants that have a high concentration of chemical defences. These insects are either resistant to the chemical substances, or they avoid areas of the plant that have high concentrations of chemicals. The larvae primarily feed in groups; they are folivores, eating plants and fruits on native trees and shrubs, though some are parasitic. However, this is not always the case; Monterey pine sawfly (Itycorsia) larvae are solitary web-spinners that feed on Monterey pine trees inside a silken web. The adults feed on pollen and nectar. Sawfly and moth larvae form one third of the diet of nestling corn buntings (Emberiza calandra), with sawfly larvae being eaten more frequently on cool days. Black grouse (Tetrao tetrix) chicks show a strong preference for sawfly larvae. Sawfly larvae formed 43% of the diet of chestnut-backed chickadees (Poecile rufescens). Insects such as ants and certain species of predatory wasps (Vespula vulgaris) eat adult sawflies and the larvae, as do lizards and frogs. Pardalotes, honeyeaters and fantails (Rhipidura) occasionally consume laid eggs, and several species of beetle larvae prey on the pupae. In some species, the larvae cluster together, reducing their chances of being killed, and in some cases form together with their heads pointing outwards or tap their abdomens up and down. Some adults bear black and yellow markings that mimic wasps. Female braconids locate sawfly larvae through the vibrations they produce when feeding, followed by inserting the ovipositor and paralysing the larva before laying eggs inside the host. These eggs hatch inside the larva within a few days, where they feed on the host. The entire host's body may be consumed by the braconid larvae, except for the head capsule and epidermis. The larvae complete their development within two or three weeks. Ten species of wasps in the family Ichneumonidae attack sawfly populations, although these species are usually rare. The most important parasitoids in this family are species in the genus Collyria. Unlike braconids, the larvae are endoparasitoids, meaning that the larvae live and feed inside the hosts body. One well known ichneumonid is Collyria coxator, which is a dominant parasitoid of C. pygmaeus. Recorded parasitism rates in Europe are between 20–76%, and as many as eight eggs can be found in a single larva, but only one Collyria individual will emerge from its host. The larva may remain inside of their host until spring, where it emerges and pupates. Several species in the family Eulophidae attack sawflies, although their impact is low. Two species in the genus Pediobius have been studied; the two species are internal larval parasitoids and have only been found in the northern hemisphere. Parasitism of sawflies by eulophids in grass exceeds 50%, but only 5% in wheat. It is unknown as to why the attack rate in wheat is low. Furthermore, some fungal and bacterial diseases are known to infect eggs and pupa in warm wet weather. Life cycle and reproduction Like all other hymenopteran insects, sawflies go through a complete metamorphosis with four distinct life stages – egg, larva, pupa and adult. Many species are parthenogenetic, meaning that females do not need fertilization to create viable eggs. Unfertilized eggs develop as male, while fertilized eggs develop into females (arrhenotoky). The lifespan of an individual sawfly is two months to two years, though the adult life stage is often very short (approximately 7 – 9 days), only long enough for the females to lay their eggs. The female uses its ovipositor to drill into plant material to lay her eggs (though the family Orussoidea lay their eggs in other insects). Plant-eating sawflies most commonly are associated with leafy material but some specialize on wood, and the ovipositors of these species (such as the family Siricidae) are specially adapted for the task of drilling through bark. Once the incision has been made, the female will lay as many as 30 to 90 eggs. Females avoid the shade when laying their eggs because the larvae develop much slower and may not even survive, and they may not also survive if they are laid on immature and glaucous leaves. Hence, female sawflies search for young adult leaves to lay their eggs on. These eggs hatch in two to eight weeks, but such duration varies by species and also by temperature. Until the eggs have hatched, some species such as the small brown sawfly will remain with them and protects the eggs by buzzing loudly and beating her wings to deter predators. There are six larval stages that sawflies go through, lasting 2 – 4 months, but this also depends on the species. When fully grown, the larvae emerge from the trees en masse and burrow themselves into the soil to pupate. During their time outside, the larvae may link up to form a large colony if many other individuals are present. They gather in large groups during the day which gives them protection from potential enemies, and during the night they disperse to feed. The emergence of adults takes awhile, with some emerging anywhere between a couple months to 2 years. Some will reach the ground to form pupal chambers, but others may spin a cocoon attached to a leaf. Larvae that feed on wood will pupate in the tunnels they have constructed. In one species, the jumping-disc sawfly (Phyllotoma aceris) forms a cocoon which can act like a parachute. The larvae live in sycamore trees and do not damage the upper or lower cuticles of leaves that they feed on. When fully developed, they cut small perforations in the upper cuticle to form a circle. After this, they weave a silk hammocks within the circle; this silk hammock never touches the lower cuticle. Once inside, the upper-cuticle's disc separates and descends towards the surface with the larvae attaching themselves to the hammock. Once they reach the round, the larvae work their way into a sheltered area by jerking their discs along. The majority of sawfly species produce a single generation per year, but others may only have one generation every two years. Most sawflies are female, making males rare. File:Cladius difformis larva.jpg|Larva File:Cladius difformis pupa dorsal.jpg|Pupa, dorsal view File:Cladius difformis pupa ventral.jpg|Pupa, ventral view File:Cladius difformis female.jpg|Female File:Cladius difformis male.jpg|Male ==Relationship with humans==

'' is a serious pest of forestry. -like larvae of Iris sawfly on yellow flag, showing damage to host plant Sawflies are major economic pests of forestry. Species in the Diprionidae, such as the pine sawflies, Diprion pini and Neodiprion sertifer, cause serious damage to pines in regions such as Scandinavia. D. pini larvae defoliated in the largest outbreak in Finland, between 1998 and 2001. Up to 75% of the trees may die after such outbreaks, as D. pini can remove all the leaves late in the growing season, leaving the trees too weak to survive the winter. Little damage to trees only occurs when the tree is large or when there is minimal presence of larvae. Eucalyptus trees can regenerate quickly from damage inflicted by the larvae; however, they can be substantially damaged from outbreaks, especially if they are young. The trees can be defoliated completely and may cause "dieback", stunting or even death. Similarly the rose sawflies, Arge pagana and A. ochropus, defoliate rose bushes. The giant woodwasp or horntail, Urocerus gigas, has a long ovipositor, which with its black and yellow colouration make it a good mimic of a hornet. Despite the alarming appearance, the insect cannot sting. The eggs are laid in the wood of conifers such as Douglas fir, pine, spruce, and larch. The larvae eat tunnels in the wood, causing economic damage. Alternative measures to control sawflies can be taken. Small-scale, mechanical methods include visually confirming larval presence on a plant and subsequently removing them, either by pruning damaged leaves or removing the larvae from the leaves they are on. Larvae typically try to remain hidden on the underside of foliage. Upon removing larvae and/or the affected leaves from plants, they may be dispatched by squishing, or, alternatively, the cut leaves with larvae still attached may be fed to birds; if larger animals do not prey upon them, other insects will. However, this is not practical or useful for some, thus the larvae can be quickly dispatched by simply dropping foliage into a vessel of plain or saltwater, diluted hydrogen peroxide or isopropyl alcohol, insecticidal soap, or other garden chemical. In large-scale, industrial settings, where beneficial insect predators can also be used to eliminate larvae, as well as parasites, which have both been previously used in control programs. Small trees can be sprayed with a number of chemicals, including maldison, dimethoate, carbaryl, imidacloprid, etc., if removing larvae from trees is not effective enough. == References ==