Volume 45, Number 3 - March 1999
Centipedes and Millipedes with Emphasis on
North America Fauna
by Rowland M. Shelley
ABOUT THIS ISSUE
Published by EMPORIA STATE UNIVERSITY
Prepared and Issued by THE DIVISION OF BIOLOGICAL SCIENCES
Editor: JOHN RICHARD SCHROCK
Editorial Committee: DAVID EDDS, TOM EDDY, GAYLEN NEUFELD
Editors Emeritus: ROBERT BOLES, ROBERT F. CLARKE
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Press Run: 15,000
Compilation: JOHN DECKER
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Online edition by: TERRI WEAST
The Kansas School Naturalist is sent free of charge and upon request to teachers, school administrators, public and school librarians, youth leaders, conservationists, and others interested in natural history and nature education. In-print back issues are sent free as long as supply lasts. Out-of-print back issues are sent for one dollar photocopy and postage/handling charge per issue. A back issue list is sent free upon request. The Kansas School Naturalist is sent free by third class mail to all U.S. zipcodes, first class to Mexico and Canada, and surface mail overseas. Overseas subscribers who wish to receive it by airmail should remit US $5.00 per year (four issues) airmail and handling. The Kansas School Naturalist is published by Emporia State University, Emporia, Kansas. Editor: John Richard Schrock, Division of Biological Sciences. Third class postage paid at Emporia, Kansas. Address all correspondence to Kansas School Naturalist, Division of Biological Sciences, Box 4050, Emporia State University, Emporia, KS 66801-5087. Opinions and perspectives expressed are those of the author(s) and/or editor and do not reflect the official position or endorsement of ESU. Kansas School Naturalist is indexed in Wildlife Review/Fisheries Review. KSNs are available at http://www.emporia.edu/ksn/ and may be downloaded for nonprofit educational use; please credit source.
Dr. Rowland M. Shelley is Curator of Terrestrial Invertebrates at the North Carolina State Museum of Natural Sciences in Raleigh, North Carolina, P.O. Box 29555, Raleigh, NC 27626-055.
Acknowledgments:I thank my colleagues R.L. Hoffman, U.S.A., and H. Enghoff, Denmark, for suggestions on the text and advice on certain topics. I also thank my friends and colleagues who assisted with the illustrations, by either taking photos or donating ones from their personal collections: H. Ellis, Z. Korsos, J. Page, and the late D.L. Tiemann and N.B. Causey. The line drawings were prepared by R.G. Kuhler, North Carolina State Museum of Natural Sciences Scientific Illustrator. - Dr. R.M. Shelley
"Prairie Fires" KSN Volume 39, No. 2 is again available upon request, thanks to a reprint grant from The Bay Foundation of New York. This color issue features spectacular prairie fire photography by Larry Schwarm and cultural and biological essays by Drs. James Hoy and Elmer Finck. Teachers may request single copies or limited classroom sets by writing to the KSN address above.
Publication and distribution of this issue of the Kansas School Naturalist was partially underwritten by contributions from readers like you.
Cover Photo: Sigmocheir maculifer (Chamberlin), a beautiful millipede of the order Polydesmida (family Xystodesmidae) occurring in the foothills of the Sierra Nevada, Fresno County, California. Photo by D.L. Tiemann.
Centipedes and Millipedes with Emphasis on North America Fauna
by Rowland M. Shelley
Centipedes (class Chilopoda) and millipedes (class Diplopoda) are the two principal classes of myriapodous, multi-legged representatives of the phylum Arthropoda, which includes organisms with exoskeletons and jointed appendages. Other arthropods include crabs, shrimp, barnacles, and lobsters (class Crustacea); insects (class Insecta); and spiders, scorpions ticks and harvestmen or daddy long-legs (class Arachnida).
HOW MANY SPECIES?
Both the Chilopoda and Diplopoda contain primarily large-bodied, macroscopic organisms that are clearly visible to the unaided eye. They are diverse classes with estimated global faunas of 10,000 species of centipedes and 80,000 species of millipedes. Currently only about 2,800 centipedes and 7,000 millipedes are described. In the United States and Canada, the millipede fauna totals around 1,400 species, but the centipedes are too poorly known to be estimated.
There are two other classes of myriapodous arthropods that lack common names. The Symphyla have 12 pairs of legs as adults; about 160 species are known. There are about 500 species of Pauropoda that have 9-11 pairs of legs as adults. They are too small to be seen with the unaided eye and are therefore unknown to the general public. These four classes were once considered orders in a "Class Myriapoda." Biologists now believe that this is not a true evolutionary category. However, "myriapods" and "myriapodous arthropods" are convenient non-scientific terms to refer to these multi-legged animals.
HOW ARE THEY DIFFERENT?
Although similar in having many legs, centipedes and millipedes are vastly different organisms and only distantly related. They suffer from a dearth of knowledgeable specialists, both now and in the past, and from erroneous information that has been passed on by word of mouth. Popularized accounts are typically superficial and inaccurate, and even chapters in zoology textbooks fail to do justice to their complexities. A need exists for accurate generalized information that can be passed on to students and the public by teachers and museum guides, but this is difficult to prepare because many statements have exceptions, especially in millipedes.
This booklet is divided into eight sections: general information and body form; legs, segments, and development; reproduction; behavior; feeding; predation and defense; and effects on humans. The information is presented with contrasting conditions of centipedes and millipedes presented together for ready comparison. Technical terminology is minimized but is unavoidable in some cases, so definitions appear in parentheses after the first usage of each term. Classifications are presented first for each class as it is often necessary to refer to a particular order; reading them is optional.
Figure 1. Outline of generalized members of A) class Pauropoda and B) class Symphyla, the other multi-legged arthropods. Drawings by R.G. Kuhler.
CLASSIFICATION OF CENTIPEDES
Class Chilopoda - This class comprises five orders distinguished by the number of legs and pedal (leg-bearing) segments, and by the degree of "heteronomy" (unequalness) or fusion in the "tergites" (the dorsal segmental plates). The orders are combined into two subclasses based on the position of the "spiracles" (openings to the tracheal or respiratory system) and the general body form.
Subclass Notostigmophora - "spriacles" are located middorsally, head is "dome shaped."
Order Scutigeromorpha (1 family) - adults with 15 pairs of legs and pedal segments; hatchlings with four; characterized by very long legs and antennae, and fusion of tergites, resulting in less than 15 dorsal plates. Occurrence: worldwide except in North America where one species has been introduced and is commonly found in drains, sinks, bathtubs, and cellars in houses.
Figure 2. Scutigera coleoprata L. from Hungary, last legs missing. Photo by Z. Korsos.
Subclass Pleurostigmophora - "spiracles" located laterally, head flattened. Forms exhibit two modes of development - "anamorphic," in which hatchlings possess less than the adult complement of legs and segments, adding legs and segments, and becoming larger, at each molt; and "epimorphic," in which hatchlings possess the full adult complement of legs and segments, and become larger at each molt.
Order Lithobiomorpha (2 families) - "anamorphic" forms; adults with 15 pairs of legs and pedal segments; hatchlings with 6-8; exhibits strong tergite"heteronomy" with alternating long and short plates. Occurrence: Worldwide.
Figure 3. A common lithobiomorph centipede in the southern Appalachian Mountains. Photo by H. Ellis.
Order Craterostigmomorpha (1 family; also only 1 genus and at most 2 species) - "anamorphic" forms, adults with 15 pairs of legs and pedal segments, hatchlings with 12. Occurrence: Tasmania and the South Island of New Zealand.
Figure 4. (right) Craterostigmus tasmanianus Pocock from Tasmania. Photo by Z. Korsos.
Order Scolopendromorpha (3 families) - "epimorphic" forms with 21 or 23 pairs of legs and pedal segments, with a low degree of tergite "heteronomy" [segments are more-or-less uniform]. Includes the largest centipedes - the aggressive, intimidating species known to the general public. Occurrence: Worldwide.
Figure 5. (left) Scolopocryptops sexspinosus (Say), a common centipede in the forests of North America east of the Central Plains. Photo by H. Ellis.
Order Geophilomorpha (11-12 families) - "epimorphic" forms with 29 or more pairs of legs and pedal segments, without tergite "heteronomy." Includes the only centipedes with 100 or more feet/legs. Occurrence: Worldwide.
Figure 6. (right) Necrophloephagus longicornis (Leach) from Denmark. Photo by Z. Korsos.
CLASSIFICATION OF MILLIPEDES
Class Diplopoda - This class comprises fifteen orders that are distinguished by the number of legs and segments, the profile and general body form, the configuration of the head, and the position of the sperm transfer or copulatory appendages in males. The orders are combined into two subclasses based on the presence or absence of calcium in the exoskeleton and copulatory structures. The great majority of millipedes possess these features, so the orders in this subclass are further grouped into two "infraclasses."
Subclass Penicillata - body soft, exoskeleton not calcified, covered with tufts of "bristles," males without copulatory appendages, reproduction occurring without contact between sexes.
Order Polyxenida (4 families) - Occurrence: Worldwide. New World occurrence from southern Canada to Brazil, especially in warmer regions.
Figure 7. Polyxenus sp., a common millipede throughout North America. Photo by D.L. Tiemann.
Subclass Chilognatha - body hard; exoskeleton calcified; setae scattered, never in tufts; males with reproductive appendages, reproduction requiring contact between sexes.
Infraclass Pentozonia - relatively short, broad millipedes; the five segmental "sclerites" (dorsal tergite, lateral pleurites, and ventral sternite) are separate; and the last one or two pairs of legs in males are modified into clasping structures called "telopods."
Order Glomeridesmida (1 family) - flattened species with 22 segments, unable to roll into balls; similar in general configuration to the presumptive ancestral millipede. Occurrence: tropical, absent from Africa.
Figure 8. (right) General body outline of a subadult Glomeridesmus sp. Drawing by R.G. Kuhler.
Order Glomerida (3 families) - 12 segments, can roll into a perfect ball or sphere. Occurrence: Europe, Asia, North Africa and North America. North American occurrence: southern Appalachians and southeastern U.S., California to northern Central America.
Figure 9. (left) Glomeris sp. from Italy. Photo by D.L. Tiemann.
Order Sphaerotheriida (2 families) - 13 segments, can roll into a perfect ball or sphere. Occurrence: Australia, New Zealand, tropical Asia, southern Africa and Madagascar.
Figure 10. (left) Sphaerotheriids from Madagascar and Indonesia. Photo by J. Page.
Infraclass Helminthomorpha - Elongate, worm-like millipedes with varying degrees of fusion among segmental sclerites; either the anterior or both pairs of legs on segment 7, or the posterior legs on segment 7 and the anterior on segment 8, are modified into copulatory appendages or "gonopods."
Order Polyzoniida (4 families) - gonopods comprised of caudal legs on segment 7 and anterior on segment 8; body arched dorsally, tergites without "paranota" [lateral expansions]; head generally subtriangular. Occurrence: North America, Caribbean, Europe, Indian Ocean islands, eastern and southern Asia. North America occurrence: southern Quebec to southern Georgia and northwestern Arkansas; southwestern British Colombia to southern Sierra Nevada and central California coast; Vera Cruz, Mexico. One additional species has been widely introduced by commerce and now occurs in Florida and along the Gulf Coast, primarily in urban environments.
Figure 11. (right) Bdellozonium cerviculatum Cook and Loomis from the Sierra Nevada, California. Photo by D.L. Tiemann.
Order Platydesmida (2 families) - gonopods comprised of caudal legs on segment 7 and anterior on segment 8; body generally flattened, tergites with "paranota"; head generally subtriangular. Occurrence: North America, Mediterranean region of Europe, east Asia (Japan, China), southeast Asia and Indonesia. North America occurrence: southern West Virginia and central Kentucky to southern Alabama, Louisiana, and western Arkansas; Idaho; northern California; Mexico to Panama.
Figure 12. (Left) Brachycybe rosea Murray, from the Sierra Nevada, California. Photo by D.L. Tiemann.
Order Siphonophorida (3 families) - gonopods comprised of caudal legs on segment 7 and anterior on segment 8; body relatively narrow, tergites without"paranota"; head prolonged into a variable "beak." Includes the millipedes with the most legs/feet. Occurrence: North, Central and South America, Caribbean, South Africa and southeast Asia. New World occurrence: central California, Arizona and Texas to southern Brazil and Peru; Greater and Lesser Antilles.
Figure 13. (left) Illacme plenipes Cook and Loomis, the world's "leggiest" animal, from San Benito County, California, left antenna missing. Photo by J. Page.
Order Stemmiulida (1 family) - gonopods comprised of anterior legs on segment 7, posterior legs on segment 7 reduced to nonfunctional remnants; body subcylindrical, tapering caudad, head with a pair of large ocelli; caudal end with spinnerets. Occurrence: Mexico to Panama, Greater and Lesser Antilles, central Africa, India, and New Guinea.
Figure 14. (Right) Head and anterior segments of Prostemmiulus sp. from Puerto Rico. Drawing by R.G. Kuhler.
Order Chordeumatida (about 32 families) - gonopods comprised of both leg pairs on segment 7; body subcylindrical, tapering caudal, toward tapered end, occasionally with paranota, 26-32 segments, caudal end with spinnerets. Occurrence: North and Central America, Chile, Europe, north Africa, Madagascar, Asia and Himalayas northward, Indonesia, Australia, and New Zealand. New World occurrence: Newfoundland, Labrador, northern British Columbia, and Alberta, to Florida, the Gulf Coast, and Panama; Chile.
Figure 15. (Left) Scoterpes copei (Packard), a cave chordeumatid from Kentucky.
Order Callipodida (4 families) - gonopods comprised of anterior legs on segment 7; body generally cylindrical and frequently ornamented with ridges and crests, 40-60 segments, caudal end with spinnerets. Occurrence: North America, Mediterranean region of Europe, Asia Minor to Pakistan, China and Vietnam. North American occurrence: southern Minnesota, Michigan, and New York to south Florida, the Gulf Coast, and northeastern Mexico; San Francisco Bay area of California, central Nevada, and Utah to southern Baja California and Sinaloa, Mexico.
Figure 16. (Right) Abacion magnum (Loomis) from North Carolina. The gonopods are shown just behind the head in the ventral view of a male. Scale in cm. Photo by T. Owens.
Order Julida (16 families) - gonopods comprised of both leg pairs on segment 7; body generally cylindrical, with conspicuous grooves or striae in two families, 30-90 segments; mostly small to moderate-size millipedes but with the longest species in North America (about 12 cm [6 1/2 inches] long). Occurrence: North America, northern Central America, Europe, Asia from Himalayas northward, and southeast Asia. A number of species have been widely introduced through human commerce, a few of which now occur globally. North American occurrence: central Alaska and northern Canada (the Yukon to northern Quebec) to southern Florida and Guatemala.
Figure 17. (Left) Cylindroiulus boleti (Koch), from Hungary. Photo by Z. Korsos.
Order Spirobolida (10 families) - gonopods comprised of both leg pairs on segment 7; body generally smooth and cylindrical, 35-60 segments; mostly moderate-size to large, robust millipedes. Occurrence: North Central and South America, Caribbean, sub-Saharan Africa, eastern and southeastern Asia to Australia. Several species have been widely introduced by human commerce, two of which now occur on tropical islands throughout the world. New World occurrence: southern Quebec, southern Michigan/Wisconsin, and Washington to southern Florida, the Gulf Coast, and southern Brazil and Peru; Greater and Lesser Antilles.
Figure 18. (Right) Four specimens of Narceus americanus (Beauvois).
Figure 19. Cambala hubrichti Hoffman (order Spirostreptida), from the southern Appalachian Mountains, North Carolina. Photo by H. Ellis.
Order Spirostreptida (11 families) - gonopods comprised of both leg pairs on segment 7; body generally smooth and cylindrical, 30-90 segments; size varying from narrow, fragile species to huge and robust, including the largest known millipedes (about 28 cm [10 1/2 inches] in length). Occurrence: Western Hemisphere, Africa, southern and southeastern Asia (south of Himalayas) to Japan, Australia. New World occurrence: western Pennsylvania and northern Idaho to northern Florida, the Gulf Coast, and Argentina; Greater and Lesser Antilles. This order includes the only native millipedes in the Hawaiian islands.
Order Polydesmida (about 28 families) - gonopods comprised of anterior legs on segment 7; body usually with 20 segments, occasionally 19, usually with variable "paranota" that impart a flattened appearance and the name "flat-back millipedes"; dorsum varying from smooth and unmodified to highly ornamented with lobes and pustules; size varying from 3-150 mm [over 6 inches]; large forms often highly colorful, with vivid red, orange, blue, and violet pigmentations in spotted or banded patterns. This order has the most species and is only one with cyanide in defensive secretions. Occurrence: Worldwide. A number of species have been widely introduced through human commerce; a few are essentially pan-global and are common in American cities. One of these is a household pest that occasionally undergoes population explosions, in which thousands of individuals overwhelm homeowners. New World occurrence: northern Quebec and southern Alaska to south Florida, the Gulf Coast, and the southern tip of South America; Greater and Lesser Antilles. [see cover]
Order Siphoniulida (1 family) - males unknown; body cylindrical, head prolonged into prominent "beak." Known only from seven females. Occurrence Guatemala; Chiapes, Mexico; Sumatra.
Figure 20. Pseudopolydesmus serratus (Say) from central North Carolina. The ventral view is of a male showing the gonopods replacing the anterior legs on segment 7.
THE MOST FREQUENTLY ASKED QUESTION: "How can you tell a centipede from a millipede?"
If it has one pair or two legs per pedal [leg bearing] segment that are clearly visible on the sides of the body, if the last legs extend backwards behind the body, and if it runs fast (excepting the Geophilomorpha) and bites or tries to bite, the animal is a centipede.
If it has two pairs or four legs on most segments that do not extend, or extend very slightly, beyond the sides of the body, if the last legs do not extend backwards behind the body, and if it moves slowly and does not attempt to bite, the animal is a millipede.
GENERAL BODY FORM
Centipedes are flexible, dorsoventrally (top-to-bottom) flattened arthropods (except for the Scutigeromorpha) that are carnivorous and adapted for speed (except for the Geophilomorpha, which moves slowly and burrows).
Millipedes are relatively inflexible arthropods with variable forms that, in general are subcylindrical; the dorsums [backs] of some species expand laterally into "paranota." They are primarily "phytosaprophagous" [feed on decaying plant material], move slowly, and are primarily adapted for burrowing in the substrate, although some species have lost this ability and are surface active; other species are too thin and weak to effectively burrow, so they inhabit existing cracks and crevices. Burrowing millipedes are important in fragmentation or shredding of leaf litter; they facilitate microbial decomposition and soil nutrient cycles; in subtropical and tropical forest habitats, millipedes may be the main debris-reducing, soil forming organisms. [See "The Role of Animals in Succession" KSN Vol. 43, No. 1, 1997]
Centipedes vary in length from around 10 to 270+ mm (about 1/2 inch to 10 1/2 inches); the largest species, Scolopendra gigantea L. (order Scolopendromorpha), occurring in South America, is among the world's largest terrestrial invertebrates and largest invertebrate carnivores. The largest North American species, Scolopendra heros Girard, occurring from Arkansas and Missouri to central Arizona and northern Mexico, grows to around 153 mm [6 inches] in length.
Millipedes vary in length from around 3-4 to 270+ mm (10 1/2 inches), the longest being Archispirostreptus gigas (Peters) (order Spirostreptida) in Africa, also among the world's largest terrestrial invertebrates. The longest North American species, Paeromopus paniculus Shelley and Bauer (order Juilda), in Yosemite National Park and vicinity, California, grows to 16 cm [6 1/2 inches] in length.
Centipedes have "poison claws" or prehensors under the head with which they kill their prey. Internal glands in these structures release the venom, and larger species can inflict a painful bite on humans. Although located under the head, the "poison claws" are actually modified legs and appendages of the first segment; they are not mouthparts and are not associated with the head. Centipedes are thus unique in being the only animals in which legs are modified into "fangs" to inject poison into other organisms.
Millipedes lack the structures to bite, pinch, or sting, and are harmless to humans, although the defensive secretions burn if they get into the eyes.
Figure 21. Ventral views of the head of a centipede (A) and millipede (B).
Centipedes occur in all habitats and are prominent in deserts and arid environments.
Millipedes occur primarily in moist deciduous forests but some species occur at high elevations in harsh "alpine" environments, and a few thrive in deserts.
Centipedes are an ancient group of terrestrial arthropods. Modern forms differentiated around the middle of the Devonian Period of the Paleozoic Era, about 380 million years ago.
Millipedes are the most ancient terrestrial arthropod group that survives today. Some of the oldest known fossils of land animals are millipedes, and modern forms had differentiated by the late Silurian Period of the Paleozoic Era, about 410 million years ago.
LEGS, SEGMENTS AND DEVELOPMENT
Centipedes adults have from 15 to 191 segments with one pair or two legs on each segment. The adult leg number therefore varies from 30 (15 pairs) to 382 (191 pairs), the latter on Gonibregmatus plurimipes Chamberlin (order Geophilomorpha), occurring in Fiji in the Pacific Ocean. Thus centipedes live up to their literal name since some species have 100 or more feet/legs.
Millipede adults have from 11 to 192 segments with two pairs or four legs on most segments. These segments are really "diplosegments" formed by fusion of adjacent segments in the embryo. The diplosegment condition is believed to have evolved in conjunction with their burrowing habits; the pushing force is more efficiently transmitted to the pushing surface when alternate segmental joints are made rigid and incompressible. The first and last segments are legless; segments 2-4 have one pair or two legs each, and the rest have two pairs or four legs except for the copulatory segment in the helminthomorph males, where one or both pairs of legs are modified into "gonopods." The adult leg number varies form 22 (11 pairs) to 750- (375 pairs), the latter on Illacme plenipes Cook and Loomis (order Siphonophorida), occurring in San Benito County, California. The next highest is on Siphonophora millepeda Loomis, on Tobago Island in the Caribbean Sea, which has up to 190 segments and 746 legs (373 pairs). Millipedes therefore don't live up to their literal name of having "1,000 feet," but 750 is a tremendous number of appendages and the most known for any animal. The words "millipede" and "thousand-legger" are figurative terms reflecting a very large number of legs.
Figure 22. Ventral view of millipede midbody segment (actually a diplosegment) of Sigmoria austrimontis Shelley from western North Carolina. The "prozontine" (P) and "metazonite" (M) correspond to the anterior and posterior of the fused embryonic segments, respectively; the legs, "spiracles" (S), and internal nerve ganglion associated with the prozonite have been relocated into the metazonite such that the prozonite, which is without structures, telescopes slightly inside the preceding metzonite. The right anterior leg is removed to show the"spriacle" beside the caudal leg. Drawing by R.G. Kuhler.
Centipedes spiracles (openings to the tracheal or respiratory system) are located laterally (on the sides of the body) or middorsally; in some forms they are valvular and can be closed.
Millipedes piracles are located ventrally; they are never valvular and cannot be closed.
Centipedes legs articulate with the body laterally and are clearly visible along both sides. This position provides little support, and the body is carried low to the substrate. The last legs extend backwards well beyond the caudal extremity of the body and are not used for locomotion.
Millipede legs articulate with the body midventrally and are not visible, or visible only very slightly, along both sides. This position provides strong support, and the body is carried high off the substrate. The last legs extend sideways like the others, not backwards behind the body. As the legs provide the pushing and burrowing power, the midventral origin allows for the longest possible legs and the greatest power with the least lateral extension, so that the legs do not extend appreciably beyond the sides of the body, where they might be broken in the narrow spaces that millipedes inhabit.
Centipedes are "opisthogoneate"; the reproductive tracts open at the caudal end of the body.
Millipedes are "progoneate"; the reproductive tracts open at the anterior end of the body, specifically on segment 3, either behind the 2nd pair of legs or on the coxae [basal segment] of these appendages.
Figure 23. Ventral view of helminthomorph millipede gonopod segment 7 of male Sigmoria austrimontis Shelley from western North Carolina. The gonopods replace the anterior legs and arise from an "aperature" [opening]. Drawing by R.G. Kuhler.
Figure 24.Stongylosoma stigmatosum (Eichwald), mating pair from Hungary. Photo by Z. Korsos.
Centipedes display mating rituals that end with the male depositing a spermatophore on the ground or in a web that he spins. Females subsequently pick up the spermatophore with their genitalia, or the male does and deposits it in the latter with his mouthparts.
Millipedes may or may not display mating rituals. In the subclass Penicillata, males deposit a spermatophore in the mesh of threads that they spin. Females then find the threads and pick up the spermatophore with their genitalia. In the infraclass Pentazonia, order Sphaerotheriida, the male clasps the anterior end of a female with his telopods, and a spermatophore is released from the openings of his reproductive tracts and transported backwards by his legs, in action similar to a conveyor belt, to near the openings of the female tracts; the female then takes the spermatopore into her mouth, but whether the sperm has left by then, or whether there is a "seminal receptacle" in her mouth is unknown. In the infraclass Pentazonia, order Glomerida, the spermatophore is deposited on a clump of earth, both of which are transported backwards to the telopods, which deposit the sperm directly into the female's openings. In the infraclass Helminthomorpha, insertion is accomplished by the "gonopods." As they are on segment 7, males must first "charge" or "load" them with sperm by bringing them into contact with the openings to their reproductive tracts on segment 3.
EGGS AND YOUNG
Centipedes exhibit both "epimorphic" and "anamorphic" growth and development. In the epimorphic orders the eggs and early post-embryonic stadia are brooded by females. In the anamorphic orders, eggs are laid singly and not brooded.
Millipedes exhibit anamorphic development, hatching form the egg usually as legless forms and then molting into stadium I with six segments and three pairs of legs. At the posterior end there are usually one or more legless segments that become leg-bearing at the following molt. Brooding of the eggs and young only occurs in the orders Platydesmida and Stemmiulida.
Centipedes are almost exclusively carnivorous and feed on a variety of smaller organisms that are seized by the "poison claws" and killed by the venom; occasionally, some chilopods feed on plants. The large scolopendromorphs can capture and eat small vertebrates, like frogs, toads, snakes, sparrows and other small birds, and mice.
Millipedes are "phytosaprophagous" and feed on decaying plant material. A few species occasionally can be carnivorous. They ingest material as they encounter it, extract the nutrients, and pass the rest. Exceptions include species with "sucking" mouthparts (long, tubular "beaks"); there is also a semiaquatic cave species in Italy whose mouthparts are modified to remove organic, clay, and limestone particles from the substrates of rivulets and moist surface of banks.
Centipede predators include beetles, spiders, salamanders, scorpions, snakes, monitor lizards, a few birds, several mammals (certain bats, shrews, rats, mongooses, and small cats and foxes), and occasionally other centipedes.
Millipede predators include a variety of invertebrates, particularly glowworm beetle larvae, and such vertebrates as hedgehogs, shrews, frogs, turtles and box terrapins, and the African mongoose. Some African beetles bury millipede carcasses.
Centipedes are primarily adapted for speed. Any long, slender object that moves forward rapidly generates lateral undulations that counter the forward movement (like the side-to-side swaying of a train), so centipedes have developed anatomical modifications to dampen or reduce the undulations. These include tergite "heteronomy" (well developed in Lithobiomorpha, poorly developed in Scolopendromorpha), which shortens the body while maintaining the same number of legs to propel it forward, and tergal fusion (in Scutigermorpha), which strengthens the body and makes it more rigid at the positions where undulations develop. The Geophilomorpha are the exception, as they are slow-moving and adapted for burrowing by elongating and contracting the body.
Millipedes are slow-moving and adapted for burrowing, for which three mechanisms are known. The burrowing power is generated by the legs, and at any moment in time, most of a millipede's legs are on the ground pushing backwards, thereby propelling the animal forward. Some millipedes have lost the ability to burrow and now are either surface active and relatively fleet (through much slower than centipedes) or inhabit cracks and crevices formed by other organisms.
1) Bulldozing: the millipede lowers its head and rams straight ahead. This behavior is shown by the cylindrical millipedes, whose bodies are of equal widths throughout, so the head prepares a path that the rest of the body can follow.
2) Wedging: the head/anterior end is inserted into a crevice and the legs, by pushing upwards and straightening, cause the crevice to widen, allowing further penetration by the anterior end. This behavior is shown by the "flat-back" millipedes, in which the paranota constitute the pushing surface and tend to split matter in a horizontal plan, like matted layers of leaves.
3) Boring: segments of progressively greater width are dragged forward, widening a crevice. In millipedes showing this behavior, the anterior end is narrow and each segment is slightly wider than the preceding one.
Centipedes use the poison claws to bit potential predators including other centipedes. The caudal legs in some Scolopendromorpha may pinch. Other defense methods include camouflage, "aposematic" [warning] coloration and luminescence, "autotomizing" or dropping of legs that are grasped by predators, and outrunning them. Some species also produce defensive secretions with a variety of noxious chemicals and larger species appear to have poison glands in their legs, as merely walking on skin can result in inflamed puncture wounds. Some lithobiomorphs emit liquid strands from glands in the caudal end that entangle potential predators.
Millipedes receive some protection from the sturdy exoskeleton. Most species can coil into protective spirals with the head in the center, and some can roll into a perfect ball or sphere. The bright "aposematic" pigmentations of colorful species serve to warn and deter potential predators, and the bioluminescence of the species of Motyxia (order Polydesmida) [the world's only bioluminescent millipedes, occurring in Tulare, Kern, and Los Angeles counties in California] probably functions as a nighttime equivalent. Otherwise, millipedes employ chemical defenses, and most have segmental defense glands that open laterally [on the side]. The defensive secretions contain a variety of noxious chemicals that deter, and possibly even kill, predators. However, millipedes do not secrete iodine, and only one order, the Polydesmida, produces cyanide.
EFFECTS ON HUMANS
Centipedes will bit humans, and the bites of large or even moderate-size scolopendromorphs and scutigeromorphs can be quite painful. Specimens should be grasped with forceps, never by hand, behind the head. Their bodies are so long and flexible that they can bend around and bite a collector if grasped at the caudal [tail] end. Bites vary with the species, but they produce moderate to severe pain for a few hours and may cause localized swelling, discoloration, and numbness. The only recorded human fatality is a child in the Philippines, who was bitten on the head and the poison was injected indirectly into the brain. If children, elderly, or allergic persons are bitten, medical assistance may be necessary. But unlike scorpions and spiders, there are no really dangerous, deadly centipedes.
Millipedes are entirely non-toxic to humans and can be picked up by hand. Some secretions discolor the skin, but this wears away in a few days without lasting effect. Some large, cylindrical, tropical species squirt their defensive secretions up to a half meter (2-3 feet) and can blind chickens and dogs. These fluids are painful if they get into the eyes, and persons working with tropical millipedes should be suitably cautious.
Important, relatively recent publications that warrant mention include texts on each class (Lewis 1981, on centipedes; Hopkin and Read 1992, on millipedes). Information on the North American fauna in the latter was updated by Shelley (1996). Other works include a generic-level classification of the Diplopoda with distributional information and nomenclatural notes (Hoffman 1980); illustrated keys to orders and families of New World millipedes (Hoffman 1990, Hoffman et al. 1996) and centipedes in the north-central states (Summers 1979); and a key to worldwide orders and families of centipedes (Mundel 1990). Checklists of North American and Central American millipede species (Chamberlain and Hoffman 1958, Loomis 1968) contain useful distributional information but are outdated; efforts are underway to update them. There is also a survey of cave millipedes in the United States (Shear 1969), which contains an illustrated key to families and genera, and valuable discussions on the latter; it has been supplemented by numerous works, most recently by Hoffman and Lewis (1997) on cave species in Indiana. Faunistic studies with keys to millipede species are available for eastern Canada (Shelley 1988) and central North Carolina (Shelley 1978, Filka and Shelley 1980), and ones without keys are available for Michigan (Snider 1991) and western Canada and Alaska (Shelley 1990a); there is also a faunistic study of Illinois centipedes that was subsequently updated (Summers et al. 1980, 1981). Older publications that are still useful include one by Bailey (1928) on New York centipedes species. Finally, there is an illustrated key to orders and families of centipedes and millipedes in Canada and the adjacent United States (Kevan and Scudder 1989), but it contains internal flaws and should be disregarded (Shelley 1990b).
Bailey, J.W. 1928. The Chilopoda of New York State with Notes on the Diplopoda. New York State Museum Bulletin No. 276: 5-50.
Chamberlin, R.V. 1918. The Chilopoda and Diplopoda of the West Indies. Bulletin of the Museum of Comparative Zoology 62: 151-262.
Chamberlin, RV and R.L. Hoffman. 1958. Checklist of the millipedes of North America. U.S. National Museum Bulletin No. 212: 1-236.
Filka, M.E. and R.M. Shelley. 1980. The milliped fauna of the Kings Mountain region of North Carolina (Arthropoda: Diplopoda). Brimleyana 4:1-45.
Hoffman, R.L. 1980 ("1979"). Classification of the Diplopoda. Museum d'Histoire Naturelle, Geneva, Switzerland, 237 pages.
Hoffman, R.L. 1990. Diplopoda. Pages 835-860 In: D.L. Dindal, ed. Soil Biology Guide. Wiley Interscience Publications, John Wiley & Sons, New York, 1349 pages + ixviii.
Hoffman, R.L. and J.J. Lewis. 1997. Pseudotremia conservata, a new cleidogonid milliped (Diplopoda, Chordeumatida), with a synopsis of the cavernicolous millipeds of the Neotropical region (Myriapoda: Diplopoda). Amazoniana 14:1-35.
Hopkin, S.P. and H.J. Read. 1992. The Biology of Millipedes. Oxford University Press, Oxford, United Kingdom.
Kevan, D.K. McE., and G.G.E. Scudder. 1989. Illustrated Keys to the Families of Terrestrial Arthropods of Canada 1. Myriapods (Millipedes, Centipedes, etc.). Biological Survey of Canada Taxonomic Series No. 1, Ottawa, 88 pages + I-VI.
Lewis, J.G.E. 1981. The Biology of Centipedes. Cambridge University Press, Cambridge, United Kingdom.
Loomis, H.F. 1968. A checklist of the millipeds of Mexico and Central America. U.S. National Museum Bulletin No. 266: 1-137.
Mundel, P. 1990. Pages 819-833 In: D.L. Dindal, ed., Soil Biology Guide. Wiley-Interscience Publication, John Wiley & Sons, New York, 1349 pages + i-xviii.
Shear, W.A. 1969. A synopsis of teh cave millipeds of the United States, with an illustrated key to genera. Psyche 76: 126-143.
Shelley, R.M. 1978. Millipeds of teh eastern Piedmont region of North Carolina, U.S.A. (Diplopoda). Journal of Natural History 12: 37-79.
Shelley, R.M. 1988. The millipeds of eastern Canada (Arthropoda: Diplopoda). Canadian Journal of Zoology 66: 1638-1663.
Shelley, R.M. 1990a. A new milliped of teh genus Metaxycheir from the Pacific Coast of Canada (Polydesmida: Xystodesmidae), with remarks on the tribe Chonaphini and the west Canadian and Alaskan diplopod fauna. Canadian Journal of Zoology 68: 2310-2322.
Shelley, R.M. 1990b. Book Review. Kevan, D.K. McE., and G.G.E. Scudder, 1989. Illustrated Keys to the Families of Terrestrial Arthropods of Canada 1. Myriapods (Millipeds, Centipedes, etc.). Pan-Pacific Entomologist 66: 177-180.
Shelley, R.M. 1996. Book Review. Stephen P. Hopkin and Helen J. Read. 1992. The Biology of Millipedes. Proceedings of teh Entomologoical Society of Washington 98: 169-172.
Snider, R.M. 1991. Updated species lists and distribution records for the Diplopoda and Chilopoda of Michigan. Michigan Academician 24: 177-194.
Summers, G. 1979. An illustrated key to the chilopods of the north-central region of the United States. Journal of the Kansas Entomological Society 52: 690-700.
Summers, G., J.A. Beatty and N. Magnuson. 1980. A checklist of Illinois centipedes (Chilopoda). Great Lakes Entomologist 13: 241-257.
Summers, G., J.A. Beatty and N.Magnuson. 1980. A checklist of Illinois centipedes (Chilopoda); Supplement. Great Lakes Entomologist 14: 59-62.
Williams, S.R. and R.A. Hefner. 1928. The millipedes and centipedes of Ohio. The Ohio State University Bulletin 33 (Ohio Biological Survey Bulletin No. 18): 92-146.
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