The

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...

Diplura ("two-pronged bristletails") is one of three orders of non-insect hexapods within the class Entognatha (alongside Collembola ( springtails) and Protura). The name "diplura", or "two tails", refers to the characteristic pair of caudal appendages or filaments at the terminal end of the body. Around 800 species of diplurans have been described, of which around 170 occur in

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

and 12 in Great Britain.Bugguide.net. Class Diplura - Two-pronged Bristletails
/ref>

Anatomy

Diplurans are typically long, with most falling between . However, some species of '' Japyx'' may reach . They have no

eye Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and conv ...

s and, apart from the darkened cerci in some species, they are unpigmented. Diplurans have long antennae with 10 or more bead-like segments projecting forward from the head. The abdomens of diplurans bear eversible vesicles, which seem to absorb moisture from the environment and help with the animal's

water balance The law of water balance states that the inflows to any water system or area is equal to its outflows plus change in storage during a time interval. In hydrology, a water balance equation can be used to describe the flow of water in and out of ...

. The body segments themselves may display several types of setae, or scales and setae. Diplurans possess a characteristic pair of cerci projecting backwards from the last of the 11 abdominal somites. These cerci may be long and filamentous or short and pincer-like, leading to occasional confusion with earwigs. Some diplurans have the ability to shed their cerci if necessary ( autotomy). Moulting occurs up to 30 times throughout the life of a dipluran, which is estimated to last up to one year. As entognaths, the mouthparts are concealed within a small pouch by the lateral margins of the head capsule. The mandibles usually have several apical teeth. Diplurans do not possess any eyes or wings. In males, glandular setae or disculi may be visible along the first abdominal sternite. External genital organs are present on the eighth abdominal segment.

Ecology

Diplurans are common in moist soil, leaf litter or

humus In classical soil science, humus is the dark organic matter in soil that is formed by the decomposition of plant and animal matter. It is a kind of soil organic matter. It is rich in nutrients and retains moisture in the soil. Humus is the Lati ...

, but are rarely seen because of their size and subterranean lifestyles. They have biting

mouthparts Mouthparts may refer to: * The parts of a mouth ** Arthropod mouthparts *** Insect mouthparts {{disambig ...

and feed on a variety of live prey and dead organic matter. Those species with long cerci are herbivorous. Diplurans are found on nearly all land masses, except Antarctica and several oceanic islands. Their role as soil-dwelling organisms may play a key role in indicating soil quality, and as a measure of

anthropogenic Anthropogenic ("human" + "generating") is an adjective that may refer to: * Anthropogeny, the study of the origins of humanity Counterintuitively, anthropogenic may also refer to things that have been generated by humans, as follows: * Human im ...

impact (e.g. soil nutrient depletion as a result of farming).

Reproduction

Like other non-insect hexapods, diplurans practice external fertilisation. Males lay up to 200 spermatophores a week, which are held off the ground by short stalks and probably only remain viable for about two days. The female collects the spermatophore with her genital opening, and later lays eggs in a cavity in the ground. The hatchlings (or nymphs) do not undergo

metamorphosis Metamorphosis is a biological process by which an animal physically develops including birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. Some inse ...

, but resemble the adults, apart from their smaller size, lesser number of setae and their lack of reproductive organs.

Lineages

Several major lineages within ''Diplura'' are readily recognizable by the structure of their cerci. *

Japygidae thumb The japygids (family Japygidae) are a taxon of hexapods, of the order Diplura, commonly known as forcepstails. In this family, the paired cerci at the end of their abdomens are pincer-like (superficially similar to the unrelated earwig ...

: possess forceps-like cerci (resembling those of an earwig). Usually very aggressive predatory diplurans, using their pincer-like cerci to capture prey, including springtails, isopods, small myriapods, insect larvae, and even other diplurans. *

Projapygidae The Projapygidae are a family of hexapods in the order Diplura The order Diplura ("two-pronged bristletails") is one of three orders of non-insect hexapods within the class Entognatha (alongside Collembola (springtails) and Protura). The ...

: possess stout, short, and rigid cerci. *

Campodeidae The Campodeidae are a family of hexapods belonging to the order Diplura. These pale, eyeless hexapods, the largest of which grow to around 12 mm in length, can be recognised by the two long, many-segmented cerci at the end of the abdomen. ...

: possess elongate, flexible cerci that may be as long as the antennae and have many segments. Feed on soil fungi, mites, springtails, and other small soil invertebrates, as well as

detritus In biology, detritus () is dead particulate organic material, as distinguished from dissolved organic material. Detritus typically includes the bodies or fragments of bodies of dead organisms, and fecal material. Detritus typically hosts commun ...

Relatives

The relationships among the four groups of hexapods are not resolved, but most recent studies argue against a

monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gro ...

Entognatha. The fossil record of the Diplura is sparse, but one apparent dipluran dates from the

Carboniferous The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carbonifero ...

. This early dipluran, '' Testajapyx'', had compound eyes, and

mouthparts Mouthparts may refer to: * The parts of a mouth ** Arthropod mouthparts *** Insect mouthparts {{disambig ...

that more closely resembled those of true insects.

References

External links

* {{Taxonbar, from=Q221563 Arthropod orders Extant Pennsylvanian first appearances