Caddisfly

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Caddisflies
Temporal range: Triassic–Recent
Trichoptera caddisfly 1.jpg
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Hexapoda
Class: Insecta
Superorder: Amphiesmenoptera
Order: Trichoptera
Kirby, 1813

The caddisflies are an order, Trichoptera, of insects with approximately 14,500 described species.[1] Also called sedge-flies or rail-flies, they are small moth-like insects with two pairs of hairy membranous wings. They are closely related to the Lepidoptera (moths and butterflies) which have scales on their wings; the two orders together form the superorder Amphiesmenoptera.

Caddisflies have aquatic larvae and are found in a wide variety of habitats such as streams, rivers, lakes, ponds, spring seeps and temporary waters (vernal pools).[2] The larvae of many species use silk to make protective cases of gravel, sand, twigs or other debris.

Etymology[edit]

The name of the order "Trichoptera" derives from the Greek: θρίξ (thrix, "hair"), genitive trichos + πτερόν (pteron, "wing"), and refers to the fact that the wings of these insects are bristly. The origin of the word "caddis" is unclear, but it dates back to at least as far as Izaak Walton's 1653 book The Compleat Angler, where "cod-worms or caddis" were mentioned as being used as bait. The term cadyss was being used in the fifteenth century for silk or cotton cloth, and "cadice-men" were itinerant vendors of such materials, but a connection between these words and the insects has not been established.[3]

Evolution and phylogeny[edit]

Eocene fossil in Baltic amber, Lithuania (44mya)

Fossil history[edit]

Fossil caddisflies have been found in rocks dating back to the Triassic;[4] the group survived the Permian–Triassic extinction event about 252 million years ago. The largest numbers of fossilised remains are those of larval cases, these being made of durable materials that preserve well. Body fossils of caddisflies are extremely rare, the oldest being from the Early and Middle Triassic, some 230 million years ago, and wings are another source of fossils.[5] The evolution of the group to one wth fully aquatic larvae seems to have taken place some time during the Triassic.[6] The finding of fossils resembling caddisfly larval cases in marine deposits in Brazil, may push back the origins of the order to the early Permian period.[5]

Evolution[edit]

Nearly all adult caddisflies are terrestrial, but their larvae and pupae are aquatic. They share this characteristic with several distantly-related groups, namely the dragonflies, mayflies, stoneflies, alderflies and lacewings.[6] The ancestors of all these groups were terrestrial, with open tracheal systems, convergently evolving different types of gills for their aquatic larvae as they took to the water to avoid predation.[6]

About 14,500 species of caddisfly in 45 families have been recognised world-wide,[1] but many more species remain to be described. Most can be divided into the suborders Integripalpia and Annulipalpia on the basis of the adult mouthparts. Integripalpian larvae construct a portable casing to protect themselves as they move around as they forage, while Annulipalpian larvae make themselves a fixed retreat in which they remain, waiting for food to come to them. The affinities of a third suborder, Spicipalpia, are unclear; they are free-living with no cases, instead creating a net-like trap with silk.[3]

Phylogeny[edit]

The cladogram of external relationships, based on a 2008 DNA and protein analysis, shows the order as a clade, sister to the Lepidoptera, and more distantly related to the Diptera (true flies) and Mecoptera (scorpionflies).[7][8][9][10]

part of Endopterygota

Antliophora

Diptera (true flies) Common house fly, Musca domestica.jpg




Mecoptera (scorpionflies) Gunzesrieder Tal Insekt 3.jpg




Boreidae (snow scorpionflies) Boreus hiemalis2 detail.jpg



Siphonaptera (fleas) Pulex irritans female ZSM.jpg







Trichoptera (caddisflies) Sericostoma.personatum.jpg



Lepidoptera (butterflies and moths) Tyria jacobaeae-lo.jpg





Hymenoptera (sawflies, wasps, ants, bees) AD2009Sep09 Vespula germanica 03.jpg




The cladogram of relationships within the order is based on a 2002 molecular phylogeny using ribosomal RNA, a nuclear elongation factor gene, and mitochondrial cytochrome oxidase. The Annulipalpia and Integripalpia are clades, but the relationships within the Spicipalpia are unclear.[11]

Trichoptera

Annulipalpia




Integripalpia



"Spicipalpia" (paraphyletic?)





Ecology[edit]

Caddisfly species can be found in all feeding guilds in stream habitats, with some species being predators, leaf shredders, algal grazers, and collectors of particles from the watercolumn and benthos.

The land caddis, Enoicyla pusilla, lives in the damp litter of the woodland floor. In the UK it is found in and around the county of Worcestershire in oakwoods.[12]

Underwater architects[edit]

Most caddisfly larvae are underwater architects and use silk, excreted from salivary glands near their mouths, for building.[13] Caddisflies can be divided loosely into three behavioral groups based on their use of silk: net-making caddisflies and case-making caddisflies, both of which may enlarge their structures throughout their larval lifespan; and free-living caddisflies, which only make such structures prior to pupation. Net-making caddisflies usually live in running water, and their nets, often made amongst aquatic vegetation, serve both as a means to collect algae, detritus, and animal food and as retreats. Case-making caddisflies may build cases exclusively of silk, but more commonly the silk holds together substrate materials such as small fragments of rock, sand, small pieces of twig or aquatic plants.

Caddisfly cases are open at both ends, the larva drawing oxygenated water through the posterior end, over their gills, and out of the wider anterior end. The anterior end is usually wider: the larva adds material to this end as it grows. Their abdomens are soft, but their tougher front ends project from their larval tubes, allowing them to walk while dragging their cases along with them. Caddisfly cases resemble bagworm cases, which are constructed by various terrestrial moths. Free-living caddisflies do not build retreats or carry portable cases until they are ready to pupate, and their bodies tend to be tougher than caddisflies that build.

Development[edit]

Pupae
Parachiona picicornis adult emerging from pupa

Caddis larvae are aquatic, with six pairs of tracheal gills on the underside of the abdomen. The larvae are long and roughly cylindrical, in most species living entirely in the tubular case that they make with silk and materials from the environment such as pieces of twig, leaf, or stone. There are five to seven larval instars, followed by an aquatic pupa which has functional mandibles (to cut through the case), gills, and swimming legs.[1]

The pupal cocoon is spun from silk, but like the larval case often has other materials attached. Species that build portable cases attach them to some underwater object, seal the front and back apertures against predators though still allowing water to flow through, and pupate within it. Once fully developed, most pupal caddisflies cut through their cases with a special pair of mandibles, swim up to the water surface, moult using the exuviae as a floating platform, and emerge as fully formed adults. They can often fly immediately after breaking from their pupal cuticle. Emergence is mainly univoltine (once per year) with all the adults of a species emerging at the same time. Development is within a year in warm places, but takes over a year in high latitudes and at high elevation in mountain lakes and streams.[1]

The adult stage of caddisflies is usually short-lived, most adults being non-feeding and equipped only to mate. Once mated, the female caddisfly lays eggs in a gelatinous mass, attaching them above or below the water surface depending on species. Eggs hatch in a few weeks.

Larva, its case containing leaf fragments and snail shells

Relationship with humans[edit]

"Silver Sedge" fishing fly mimicking Lepidostoma caddisfly, from Trout fly-fishing in America
"Limnephilus elegans the Elegant Grannom", from British Entomology by John Curtis, c. 1840

In angling[edit]

Caddisflies are called sedges by anglers. Individual species emerge en masse at different times, and are used one after the other, often for only a few days each year, as models for artificial fishing flies for fly fishing in trout streams. Each type has its own angling name, so for example Mystacides is the dancer; Sericostoma the caperer; Leptocerus the silverhorn; Phryganea the murragh or great red sedge; Brachycentrus subnubilis the grannom; Lepidostoma the silver sedge.[12]

As bioindicators[edit]

Caddisflies are useful as bioindicators (of good water quality), since they are sensitive to water pollution, and are large enough to be assessed conveniently in the field. Some species indicate undisturbed habitat, and some indicate degraded habitat.[14] Although caddisflies may be found in waterbodies of varying qualities, species-rich caddisfly assemblages are generally thought to indicate clean water bodies, such as lakes, ponds, and marshes. Together with stoneflies and mayflies, caddisflies feature importantly in bioassessment surveys of streams and other water bodies.[15]

In art[edit]

While caddisflies in the wild construct their cases out of twigs, sand, aquatic plants, and rocks, the French artist Hubert Duprat makes art by providing wild caddisflies with precious stones and other materials. He collected caddisfly larvae from the wild and put them in climate-controlled tanks. He removes the larvae from their original cases and adds precious and semi-precious items into the tank. The larvae then build new cases out of precious items, creating a unique form of artwork. The resulting works are sold across the world.[16]

Taxonomy[edit]

There are roughly 14,500 species in some 45 families worldwide.[1]

References[edit]

  1. ^ a b c d e Gullan, P. J.; Cranston, P. S. (2010). The Insects: An Outline of Entomology (4th ed.). Wiley. pp. 522–523. ISBN 978-1-118-84615-5. 
  2. ^ Glenn B. Wiggins, Larvae of the North American Caddisfly General (Trichoptera), 2nd. ed. (Toronto: University Press, 1996), p. 3
  3. ^ a b Wiggins, Glenn B. (2015). "1". Caddisflies: The Underwater Architects. University of Toronto Press. ISBN 978-1-4426-5617-8. 
  4. ^ Howell V. Daly, John T. Doyen & Alexander H. Purcell (1998). Introduction to Insect Biology and Diversity (2nd ed.). Oxford University Press. p. 320. ISBN 0-19-510033-6. 
  5. ^ a b Mouro, Lucas D. ; Zatoń, Michał; Fernandes, Antonio C.S.;Waichel, Breno L. (2015). "Larval cases of caddisfly (Insecta: Trichoptera) affinity in Early Permian marine environments of Gondwana". Nature. 6. doi:10.1038/srep19215. 
  6. ^ a b c Wiggins, Glenn B. (2015). Caddisflies: The Underwater Architects. University of Toronto Press. p. Introduction. ISBN 978-1-4426-5617-8. 
  7. ^ Whiting, Michael F.; Whiting, Alison S.; Hastriter, Michael W.; Dittmar, Katharina (2008). "A molecular phylogeny of fleas (Insecta: Siphonaptera): origins and host associations". Cladistics. 24 (5): 1–31. doi:10.1111/j.1096-0031.2008.00211.x. 
  8. ^ Yeates, David K.; Wiegmann, Brian. "Endopterygota Insects with complete metamorphosis". Tree of Life. Retrieved 24 May 2016. 
  9. ^ Whiting, Michael F. (2002). "Mecoptera is paraphyletic: multiple genes and phylogeny of Mecoptera and Siphonaptera". Zoologica Scripta. 31 (1): 93–104. doi:10.1046/j.0300-3256.2001.00095.x. 
  10. ^ Wiegmann, Brian; Yeates, David K. (2012). The Evolutionary Biology of Flies. Columbia University Press. p. 5. ISBN 978-0-231-50170-5. 
  11. ^ Kjer, K. M.; Blahnik, R. J.; Holzenthal, R. W. (April 2002). "Phylogeny of Trichoptera (caddisflies): characterization of signal and noise within multiple datasets". Syst. Biol. 51 (2): 385–387. 
  12. ^ a b Marren, Peter; Mabey, Richard (2010). Bugs Britannica. Chatto & Windus. pp. 156–157. ISBN 978-0-7011-8180-2. 
  13. ^ Wiggins, Larvae of the North American Caddisfly, p. 28
  14. ^ Pereira, Lilian R.; et al. (2012). "Trichoptera as bioindicators of habitat integrity in the Pindaı ́ ba river basin, Mato Grosso (Central Brazil)" (PDF). Ann. Limnol. 48: 295–302. 
  15. ^ "Biomonitoring Macroinvertebrates-Stoneflies, Monitoring and Assessment, Bureau of Land and Water Quality, Maine Department of Environmental Protection". www.maine.gov. Retrieved 2016-02-23. 
  16. ^ "Artist Hubert Duprat Collaborates with Caddisfly Larvae as They Build Aquatic Cocoons from Gold and Pearls". Colossal. Retrieved 17 April 2017. 

Further reading[edit]

A useful reference to the larvae of the British Trichoptera is "Caddis Larvae" Norman E. Hickin (1967) Hutchinson & Co. Ltd. London.

External links[edit]