Megaloptera
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Megaloptera is an order of
insect Insects (from Latin ') are Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (Insect morphology#Head, head, ...
s. It contains the alderflies, dobsonflies and fishflies, and there are about 300 known
species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
. The order's name comes from
Ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...
, from ''mega-'' (μέγα-) "large" + ''pteryx'' (πτέρυξ) "wing", in reference to the large, clumsy wings of these insects. Megaloptera are relatively unknown insects across much of their range, due to the adults' short lives, the aquatic larvae's often-high tolerance of
pollution Pollution is the introduction of contaminants into the natural environment that cause harm. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, the component ...
(so they are not often encountered by swimmers etc.), and the generally
crepuscular In zoology, a crepuscular animal is one that is active primarily during the twilight period, being matutinal (active during dawn), vespertine (biology), vespertine/vespertinal (active during dusk), or both. This is distinguished from diurnalit ...
or
nocturnal Nocturnality is a ethology, behavior in some non-human animals characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnality, diurnal meaning the opposite. Nocturnal creatur ...
habits. However, in the
Americas The Americas, sometimes collectively called America, are a landmass comprising the totality of North America and South America.''Webster's New World College Dictionary'', 2010 by Wiley Publishing, Inc., Cleveland, Ohio. When viewed as a sing ...
the dobsonflies are rather well known, as their males have tusk-like mandibles. These, while formidable in appearance, are relatively harmless to humans and other animals; much like a
peacock Peafowl is a common name for two bird species of the genus '' Pavo'' and one species of the closely related genus '' Afropavo'' within the tribe Pavonini of the family Phasianidae (the pheasants and their allies). Male peafowl are referred t ...
's feathers, they serve mainly to impress females. However, the mandibles are also used to hold females during mating, and some male dobsonflies spar with each other in courtship displays, trying to flip each other over with their long mandibles. Dobsonfly larvae, commonly called hellgrammites, are often used for
angling Angling (from Old English ''angol'', meaning "hook") is a fishing technique that uses a fish hook attached to a fishing line to tether individual fish in the mouth. The fishing line is usually manipulated with a fishing rod, although rodless te ...
bait in North America. The Megaloptera were formerly considered part of a group then called Neuroptera, together with
lacewing The Hemerobiiformia are a suborder of insects in the order Neuroptera that include most of the lacewings, antlions and their allies. The phylogeny of the Neuroptera was explored in 2014 using mitochondrial DNA sequences. The results indicate t ...
s and snakeflies, but these are now generally considered to be separate orders, with Neuroptera referring to the lacewings and relatives (which were formerly called Planipennia). The former Neuroptera, particularly the lacewing group, are nonetheless very closely related to each other, and the new name for this group is
Neuropterida The Neuropterida are a clade of holometabolous insects, sometimes placed at the superorder level. The clade contains the orders Neuroptera (lacewings, antlions), Megaloptera (alderflies, dobsonflies), and Raphidioptera (snakeflies), and includes ...
. This is either placed at superorder rank, with the
Holometabola Holometabola (from Ancient Greek "complete" + "change"), also known as Endopterygota (from "inner" + "wing" + Neo-Latin "-having"), is a supra-order (biology), ordinal clade of insects within the infraclass Neoptera that go through distincti ...
—of which they are part—becoming an unranked
clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...
above it, or the Holometabola are maintained as a superorder, with an unranked Neuropterida being a part of them. Within the holometabolans, the closest living relatives of the neuropteridan clade are the
beetle Beetles are insects that form the Taxonomic rank, order Coleoptera (), in the superorder Holometabola. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 40 ...
s. The Asian dobsonfly '' Acanthacorydalis fruhstorferi'' can have a wingspan of up to , making it the largest aquatic insect in the world by this measurement.


Anatomy and life cycle

Adult megalopterans closely resemble the lacewings, except for the presence of a pleated region on their hindwings, helping them to fold over the abdomen. They have strong mandibles and mouthparts apparently adapted for chewing, although many species do not eat as adults. They have large
compound eye A compound eye is a Eye, visual organ found in arthropods such as insects and crustaceans. It may consist of thousands of ommatidium, ommatidia, which are tiny independent photoreception units that consist of a cornea, lens (anatomy), lens, and p ...
s, and, in some species, also have
ocelli A simple eye or ocellus (sometimes called a pigment pit) is a form of eye or an optical arrangement which has a single lens without the sort of elaborate retina that occurs in most vertebrates. These eyes are called "simple" to distinguish the ...
. The wings are large and subequal. The female may lay up to 3,000 eggs in a single mass, placing them on vegetation overhanging water. Megaloptera undergo the most rudimentary form of complete metamorphosis among the insects. There are fewer differences between the larval and adult forms of Megaloptera than in any other order of holometabolous insects, and their aquatic
larva A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect development such as insects, some arachnids, amphibians, or cnidarians typically have a larval phase ...
e dwell in fresh water, around which the adults also live. The larvae are
carnivorous A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose nutrition and energy requirements are met by consumption of animal tissues (mainly mu ...
, and are known to feed on small invertebrates, such as crustaceans, clams, worms and other insects. They possess strong jaws that they use to capture their prey. They have large heads and elongated bodies. The abdomen bears a number of fine tactile filaments, which, in some species, may include
gill A gill () is a respiration organ, respiratory organ that many aquatic ecosystem, aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow r ...
s. The final segment of the abdomen bears either a pair of
proleg A proleg is a small, fleshy, stub structure found on the ventral surface of the abdomen of most larval forms of insects of the Order (biology), order Lepidoptera, though they can also be found on larvae of insects such as symphyta, sawflies. In ...
s, or a single, tail-like appendage. The larvae grow slowly, taking anywhere from 1 to 5 years to reach the last larval stage. When they reach maturity, the larvae crawl out onto land to
pupa A pupa (; : pupae) is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in their life cycle, the stages th ...
te in damp soil or under logs. Unusually, the pupa is fully motile, with large mandibles that it can use to defend itself against predators. The short-lived adults emerge from the pupa to mate - many species never feed as adults, living only a few days or hours, up to a few weeks at most.


Evolution

Apart from the two living families, there are a few prehistoric
taxa In biology, a taxon (back-formation from ''taxonomy''; : taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and ...
sometimes placed Megaloptera, only known from
fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...
s. * Family Corydasialidae (Other authors place as members of
Neuroptera The insect order (biology), order Neuroptera, or net-winged insects, includes the lacewings, mantidflies, antlions, and their relatives. The order consists of some 6,000 species. Neuroptera is grouped together with the Megaloptera (alderflies, f ...
) * Family Parasialidae (placement within the
Neuropterida The Neuropterida are a clade of holometabolous insects, sometimes placed at the superorder level. The clade contains the orders Neuroptera (lacewings, antlions), Megaloptera (alderflies, dobsonflies), and Raphidioptera (snakeflies), and includes ...
uncertain) * Family Euchauliodidae (other authors have suggested that this likely represents a " grylloblattid" instead) * Family Nanosialidae (other authors consider this family more closely related to snakeflies) The Megaloptera are monophyletic and are a sister clade of the
Neuroptera The insect order (biology), order Neuroptera, or net-winged insects, includes the lacewings, mantidflies, antlions, and their relatives. The order consists of some 6,000 species. Neuroptera is grouped together with the Megaloptera (alderflies, f ...
.Wang, Y.; Liu, X.; Winterton, S. L. & Yang, D. (2012). "The first mitochondrial genome for the fishfly subfamily Chauliodinae and implications for the higher phylogeny of Megaloptera". ''PLoS One''. 7 (10): e47302. Within the Megaloptera, Corydalinae and Chauliodinae are sister clades. The oldest fossils confidently identifiable as megalopterans date to the Early
Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately 143.1 Mya. ...
.


Footnotes


References

* * (2005): ''Evolution of the Insects''.
Cambridge University Press Cambridge University Press was the university press of the University of Cambridge. Granted a letters patent by King Henry VIII in 1534, it was the oldest university press in the world. Cambridge University Press merged with Cambridge Assessme ...
. * (2007): The neuropterid fauna of Dominican and Mexican amber (Neuropterida, Megaloptera, Neuroptera). ''American Museum Novitates'' 3587: 1-58
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External links

* Oswald, John D. (2023)
Neuropterida Species of the World. Lacewing Digital Library, Research Publication No. 1.
(an online catalog that includes data on the Megaloptera species of the world) * Oswald, John D. (2023)
Bibliography of the Neuropterida. Lacewing Digital Library, Research Publication No. 2.
(an online bibliography that includes data on the global scientific literature of the order Megaloptera)
Lacewing Digital Library
(a web portal that provides access to a suite of online resources that contain data on the order Megaloptera) {{Authority control Insect orders Cisuralian first appearances Extant Permian first appearances Neuropterida