Author: Bruce Neville
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|Scientific Name: Taxidea taxus
Common Name: Two-tailed Bristletails
Diplurans are generally small, soft-bodied, wingless, whitish insects. Most are just a few millimeters in length, though the Australian species Heterojapyx gallardi can reach 50 mm in length. The head bears a pair of segmented antennae. The chewing mouthparts are enclosed in a pounch on the underside of the head. There are no eyes. Each of the three thoracic appendages bears a pair of legs, each with five segments. The slender abdomen of 10 segments may be cylindrical or dorsoventrally flattened. The first seven abdominal segments bear short appendages (called styli, singular stylus) and an eversible sac. The body is covered with setae, or less commonly, scales, which are important in the identification of species. The name diplura means “two-tailed,” and the end of the abdomen bears two appendages, called cerci. The cerci are long, segmented filaments in the Campodeidae and short, thick forceps in the Japygidae. The filamentous cerci of campodeids make them look much like the closely related bristletails or silverfish (order Thysanura), which always have three abdominal appendages. The forceps-like cerci of the japygids make them look much like minute earwigs (order Dermaptera), but earwigs have wings and compound eyes, both of which are absent in diplurans.
Members of the order Diplura occur on all continents except Antarctica, generally in tropical or temperate areas. There are approximately 800 species of diplurans in the world, classfied into 7-9 families, depending on the source consulted. Approximately 60-70 species in 5 or 6 families occur in the United States. California probably has more species than any other state. The two largest families are the Campodeidae and the Japygidae. Some species are essentially worldwide in distribution, while others have very limited ranges.
Species of both Campodeidae and Japygidae are found in New Mexico, although they have not necessarily been identified to species. Several species have been found in the mountains of southeastern Arizona, so searches in New Mexico will probably turn up several species of diplura here, as well. There are no published records of the worldwide species Campodea fragilis from New Mexico, but it occurs in adjacent states, so it probably occurs here, as well. A Plusiocampa species (family Campodeidae) is widely distributed throughout Carlsbad Caverns. It also occurs in several other caves in Eddy County, New Mexico.
Diplurans in general occur in the soil in moist microhabitats, such as under rocks or logs. Japygid diplurans are often found a foot or more below the surface of the soil. Campodeid diplurans have been collected in lichen crusts in New Mexico.
A number of species throughout the world are associated with caves. The Plusiocampa species in the Eddy County caves is a true troglobite. It is usually found on or near organic material (Welbourn, 1978). All specimens collected by Welbourn in Ogle Cave were within the dark zone.
Diplurans appear to be generalist feeders, although animal prey seems to make up the largest part of the diet. Most will feed on any invertebrates they can capture, including small insects and their larvae, mites, and other diplurans. All types of diplurans also feed upon both living and dead vegetable matter, fungal spores, and detritus.
Welbourn (1978) suggested that Plusiocampa in Eddy County caves probably feed on dead camel crickets, Ceuthophilus species. Ferguson (1990) reported that cavernicolous campodeids ingest sediment to gain nutrition from the bacteria or other organic matter present.
Diplurans are preyed upon by a variety of predatory arthropods, including other diplurans. The remains of diplurans have also been found in the stomach contents of treefrogs in Brazil (Peltzer and Lajmanovich, 2001).
Reproduction and Development:
Diplurans do not exhibit courtship behavior. Male diplurans deposit stalked packets of sperm (called spermatophores) on the substrate, whether females are nearby or not. A single male may deposit as many as 200 spermatophores per week. Spermatozoa remain viable for only a couple days. Females with mature eggs seek out these spermatophores and insert them into the genital opening. From 4 to 9 eggs are laid in stalked clusters suspended from stones, pebbles, or the sides of the burrow, so that they are not in contact with the moist soil. Female japygids show protective behavior, curling around the egg cluster like a centipede. Such behavior has apparently not been documented in campodeids.
The eggs hatch in 12-13 (campodeids) to 15 (japygids) days. The first (campodeid) or first two (japygid) larval stages last only a few days and do not move or feed. In the Japygidae, these larval stages are also guarded by the mother. The forceps appear in the japygids after the second larval stage, and the young leave the protection of their mother.
All diplurans exhibit simple metamorphosis, in which the larvae look like small adults. Immature diplurans lack the complete adult arrangement of setae. Sexual maturity is apparently reached in the fourth instar of japygids; the number of molts prior to sexual maturity is not recorded for campodeids. Diplurans continue to molt as adults, and as many as 30 molts have been recorded over a lifespan of over two years (Cole, 2004).
Both campodeids and japygids are excellent burrowers. Campodeids generally dig their own burrows with wormlike movements of the body, while japygids use their short, but strong legs to enlarge existing channels in the soil.
Prey are detected by the highly sensory antennae. Campodeids are good runners and capture their prey by chasing, while the relatively short legs of japygids are not suited for running, so they lie in wait to grasp their prey with the abdominal forceps.
The forceps of japygids are also used in defense. The cerci of campodeids can break off to fool predators. They are regrown at the next molt.
Diplurans are detritivores and predators of small organisms as well as providing prey for other predators of small arthropods. Some diplurans have been suspected of being minor agricultural pests. The Plusiocampa in Eddy County is one of the most common invertebrates in several of the caves studied, so they are probably important in recycling dead organisms and providing food for other predatory invertebrates.
Populations of diplurans are not well known, so no species is listed as protected. Some species outside New Mexico apparently have very limited ranges, which would make them vulnerable. Other species apparently adapt well to human environments; Cole (2004) reports that considerable diversity of diplurans have been recorded in the vicinity of Vienna Austria. Troglobitic species, such as the Plusiocampa in New Mexico may be at risk from habitat disturbance.
Main Families: Campodeidae, Japygidae
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Barr, Thomas C., Jr., and James R. Reddell. 1967. The arthropod cave fauna of the Carlsbad Caverns region, New Mexico . Southwestern Naturalist 12(3): 253-274.
Borror, Donald J., and Richard E. White. 1970. A Field Guide to the Insects of American North of Mexico. Peterson field guide series, no. 19. Boston: Houghton Mifflin.
Cole, Jeffrey A. 2004. Diplura (Diplurans). pp. 107-111 in: Grzimek's Animal Life Encyclopedia, 2nd ed. Vol. 3: Insects. Detroit : Thompson Gale.
Ferguson, Lynn M. 1990. Insecta: Diplura. Pp. 951-963 in: Dindal, Daniel L., ed. Soil Biology Guide. New York : John Wiley & Sons.
Maddison, David R. 1995. Diplura. Tree of Life Web Project, URL= http://tolweb.org/tree?group=Diplura&contgroup=Hexapoda. Accessed 11 September 2004.
Meyer, John R. 2001. Diplura. http://www.cals.ncsu.edu/course/ent425/compendium/diplura.html. Accessed 11 September 2004.
Nearctica.com. 1998. Nearctica – Diplura. [A listing of recognized species from North America north of Mexico.] URL= http://www.nearctica.com/nomina/oddbugs/diplura.htm. Accessed 11 September 2004.
Peltzer, Paola M., and Rafael C. Lajmanovich. 2001. Hyla raniceps (NCN), diet. Herpetological Review 32(4):247-248.
Reddell, James R. 1983. A checklist and bibliography of the Japygoidea (Insecta: Diplura) of North America, Central America, and the West Indies. The Pearce-Sellards Series (Texas Memorial Museum), no. 37:1-41.
Welbourn, W. Calvin. 1978. Biology of Ogle Cave with a list of the cave fauna of Slaughter Canyon. NSS Bulletin 40(1):27-34.