Sawfly

This article is about the hymenopteran. For the moth, see Symphyta (moth genus).
Sawfly
Temporal range: Triassic - Recent
Large rose sawfly
Arge pagana stephensii
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Suborder: Symphyta
Superfamilies and families

Superfamily Cephoidea
   Family Cephidae
Superfamily Megalodontoidea
   Family Megalodontesidae
   Family Pamphiliidae
Superfamily Orussoidea
   Family Orussidae
Superfamily Siricoidea
   Family Anaxyelidae
   Family Siricidae
Superfamily Tenthredinoidea
   Family Argidae
   Family Blasticotomidae
   Family Cimbicidae
   Family Diprionidae
   Family Pergidae
   Family Tenthredinidae
Superfamily Xyeloidea
   Family Xyelidae
   Family Xiphydriidae

Sawfly is the common name for insects belonging to suborder Symphyta of the order Hymenoptera. Sawflies are distinguishable from most other hymenopterans by the broad connection between the abdomen and the thorax, and by their caterpillar-like larvae. The common name comes from the saw-like appearance of the ovipositor, which the females use to cut into the plants where they lay their eggs. Large populations of certain sawfly species can cause substantial economic damage to forests and cultivated plants.

Taxonomy

Sawfly ovipositing

Sawflies are a group of largely phytophagous insects. The overall group is paraphyletic, but the name is still in common use, and treated as a suborder, though it likely will be phased out in future classifications. These superfamilies are regarded as the most primitive taxa within the Hymenoptera (some going back 200 million years), and one of the taxa within the Symphyta gave rise to the suborder Apocrita (wasps, bees, and ants - this group is considered monophyletic). In the opinion of many experts, the most likely sister taxon to the Apocrita is the family Orussidae, the only symphytan group which is parasitic.

Fossils in the family Xyelidae are regarded as the oldest of all insects known in Hymenoptera, dating back to the Lower Triassic from rocks collected in the Soviet Union.[1]

Description

Larvae

Some larvae look like caterpillars (the larvae of moths and butterflies), with some notable differences; (1) they have six or more pairs of prolegs (sometimes greatly reduced and difficult to see) on the abdomen, while caterpillars have five pairs or fewer, (2) they have two stemmata instead of a caterpillar's six, (3) caterpillars (except for a tiny minority) always have the two first abdominal segments legless, and (4) sawfly larvae have an invariably smooth head capsule with no cleavage lines, while lepidopterous caterpillars bear an inverted "Y" or "V" (adfrontal suture). Typical sawfly larvae are herbivorous, the group feeding on a wide range of plants. Individual species, however, are often quite specific in their choice of plants used for food. The larvae of various species exhibit leaf-mining, leaf "rolling", or gall formation. Three families are strictly xylophagous, and called "wood wasps", and one family is parasitic. The larvae that do not feed externally on plants are grub-like, without prolegs. When harassed, many sawfly larvae are able to squirt a foul liquid from their last segment.

Adults

Bristly rose sawfly Cladius difformis, above millimeter scale

Adult sawflies, except for those in the family Cephidae, have structures that latch onto the underside of the fore wings to help hold the wings in place when the insect is at rest. These "cenchri", which are absent in the suborder Apocrita, are located behind the scutellum on the thorax. Adults of some species are carnivorous, eating other insects, but many also feed on nectar. Adults also have stronger antennae. Among the largest sawfly ever discovered was Hoplitolyda duolunica from the Mesozoic, with a body length of 55 millimetres (2.2 in) and a wingspan of 92 millimetres (3.6 in).[2]

Ecology

Group of sawfly larvae feeding on leaves

Sawflies are 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.[3] The larvae primarily feed in groups; they are folivores, consuming plants and fruits on native trees and shrubs, though some are parasitic.[4][5][6] 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.[7] The adults feed on pollen and nectar.[4]

Schematic preview of the sawflies found in the regions of Pijanec and Maleš in Macedonia (with legends on Macedonian and English)

Sawflies are eaten by a wide variety of predators. Both adults and larvae, along with other insects, are an essential food source for stonechat (Saxicola) birds.[8] The larvae are also important for partridge chicks.[9] Based on a study, the diet of nestling corn buntings (Emberiza calandra), the larvae of sawflies and moths compromised one third of their diet, although sawfly larvae would be eaten more frequently on cool days in comparison in warm temperatures. The larvae are not regarded as important to the diet of corn buntings.[10] Black grouse (Tetrao tetrix) chicks show a preference for sawfly larvae which makes them one of the most consumed invertebrates by them.[11][12] Even if there are high populations of other insects, the chicks still predominately feed on the larvae. Sawfly larvae compromised 43% of the diet of chestnut-backed chickadees (Poecile rufescens).[7] Small mammals prey on sawfly cocoons, causing high mortality rates among them. These predators include the masked shrew (Sorex cinereus), the northern short-tailed shrew (Blarina brevicauda) and the deer mouse (Peromyscus maniculatus).[13] Insects such as ants and certain species of predatory wasps (Vespula vulgaris) eat sawflies.[14][15]

Spitfire sawfly in a group together on a tree: Larvae that group together are less likely to die from predators.

The larvae have several defensive tactics against predators. While adults are unable to sting, the larvae regurgitate a liquid from their mouths which is distasteful and irritating to potential predators, which makes them avoid the larvae.[5] The larvae also cluster together which reduces their chances of getting killed, and in some cases, a group of larvae will form together with their heads pointing outwards or tap their abdomens up and down.[16]

Parasites

Sawflies are hosts to many parasitoids, most of which are parasitic Hymenoptera; more than 40 species known to attack them. However, fewer than 10 of these species actually cause a significant impact on sawfly populations.[17]

See also

References

  1. ↑ Hermann, Henry R. (1979). Social Insects 1. Oxford: Elsevier Science. p. 85. ISBN 978-0-323-14979-2.
  2. ↑ Gao, Taiping; Shih, Chungkun; Rasnitsyn, Alexandr P.; Ren, Dong; Laudet, Vincent (2013). "Hoplitolyda duolunica gen. et sp. nov. (Insecta, Hymenoptera, Praesiricidae), the Hitherto Largest Sawfly from the Mesozoic of China". PLoS ONE 8 (5): e62420. Bibcode:2013PLoSO...862420G. doi:10.1371/journal.pone.0062420. PMC 3643952. PMID 23671596.
  3. ↑ Rosenthal, Gerald A.; Berenbaum, May R. (1991). Herbivores Their Interactions with Secondary Plant Metabolites. (2nd ed.). Oxford: Elsevier Science. p. 190. ISBN 978-0-323-13940-3.
  4. 1 2 "Sawflies (Tenthredinoidae)". BBC. Retrieved 11 August 2015.
  5. 1 2 Australian Museum (20 October 2009). "Animal Species:Sawflies". Retrieved 11 August 2015.
  6. ↑ Bandeili, Babak; Müller, Caroline (2009). "Folivory versus florivory—adaptiveness of flower feeding". Naturwissenschaften 97 (1): 79–88. Bibcode:2010NW.....97...79B. doi:10.1007/s00114-009-0615-9. PMID 19826770.
  7. 1 2 Kleintjes, P. K.; Dahlsten, D. L. (1994). "Foraging Behavior and Nestling Diet of Chestnut-Backed Chickadees in Monterey Pine" (PDF). The Condor 96 (3): 647–653. doi:10.2307/1369468. JSTOR 1369468.
  8. ↑ Cummins, S.; O'Halloran, J. (2002). "An assessment of the diet of nestling Stonechats using compositional analysis: Coleoptera (beetles), Hymenoptera (sawflies, ichneumon flies, bees, wasps and ants), terrestrial larvae (moth, sawfly and beetle) and Arachnida (spiders and harvestmen) accounted for 81% of Stonechat nestling diet.". Bird Study 49 (2): 139–145. doi:10.1080/00063650209461258.
  9. ↑ Campbell, L.H.; Avery, M.I.; Donald, P.; Evans, A.D.; Green, R.E.; Wilson, J.D. (1997). A Review of the Indirect Effects of Pesticides on Birds (PDF) (Report). Peterborough, UK: Joint Nature Conservation Committee, Report. no 227. p. 27. ISSN 0963-8091. line feed character in |title= at position 12 (help)
  10. ↑ Brickle, N. W.; Harper, D. G. C. (1999). "Diet of nestling Corn Buntings Miliaria calandra in southern England examined by compositional analysis of faeces". Bird Study 46 (3): 319–329. doi:10.1080/00063659909461145.
  11. ↑ Starling-Westerberg, A. (2001). "The habitat use and diet of Black Grouse Tetrao tetrix in the Pennine hills of northern England". Bird Study 48 (1): 76–89. doi:10.1080/00063650109461205.
  12. ↑ Cayford, J.T. (1990). "Distribution and habitat preferences of Black Grouse in commercial forests in Wales: conservation and management implications". Proceedings of the International Union Game of Biologists Congress 19: 435–447.
  13. ↑ Holling, C. S. (1959). "The Components of Predation as Revealed by a Study of Small-Mammal Predation of the European Pine Sawfly" (PDF). The Canadian Entomologist 91 (5): 293–320. doi:10.4039/Ent91293-5.
  14. ↑ Müller, Caroline; Brakefield, Paul M. (2003). "Analysis of a Chemical Defense in Sawfly Larvae: Easy Bleeding Targets Predatory Wasps in Late Summer". Journal of Chemical Ecology 29 (12): 2683–2694. doi:10.1023/B:JOEC.0000008012.73092.01. ISSN 1573-1561. PMID 14969355.
  15. ↑ Petre, Charles-Albert; Detrain, Claire; Boevé, Jean-Luc (2007). "Anti-predator defence mechanisms in sawfly larvae of Arge (Hymenoptera, Argidae)". Journal of Insect Physiology 53 (7): 668–675. doi:10.1016/j.jinsphys.2007.04.007. PMID 17540402.
  16. ↑ Phillips, Charlma (December 1992). "Spitfires – Defoliating Sawflies" (PDF). Department of Primary Industries and Resources. Government of South Australia. Retrieved 11 August 2015.
  17. ↑ Capinera 2008, p. 1827.

Further reading

External links

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