Zoraptera

(invertebrate zoology) An order of insects, related to termites and psocids, which live in decaying wood, sheltered from light; most individuals are wingless, pale in color, and blind.

(Zorapterans)

Class: Insecta

Order: Zoraptera

Number of families: 1

Evolution and systematics

Zoraptera is a small order of exopterygote neopteran insects, for which the only general common name is zorapterans, although "angel insects" occasionally has been used. The affinities of Zoraptera have long been debated, and the order has been regarded as distinct but difficult to place phylogenetically. The major point of contention is whether they are primitive Paraneoptera (and thereby allied with bugs, lice, and their relatives), are related to cockroaches (Blattodea), or perhaps are descendants of some pre-dictyopteran insect stock. Other suggested alliances, based in part on the presence of distinct cerci, are as a sister group of the termites (Isoptera) or the webspinners (Embioptera). Although it has not yet been studied for many species, wing structure allies them most closely with cockroaches and their allies, with recent authors believing them to be primitive Blattoneoptera that separated early from the main lineage. There are no known fossils, other than for one species (Zorotypus palaeus) from Dominican amber (Lower Miocene/Upper Eocene).

All Zoraptera have been placed in the single family Zorotypidae. Suggestions that the New World taxa may constitute a separate family, as yet unnamed, need further verification. Until recently, all the 30 described species were allocated to the single genus Zorotypus. In 1993 six additional genera (Brazilozoros, Centrozoros, Floridazoros, Latinozoros, Meridozoros, and Usazoros) were erected, based on wing venation. All of these genera contain one species and are from the New World. All Old World species are placed in Zorotypus. Zorotypus is now a "holding genus" for the many species for which venation is unknown. Species identification often is difficult, with the females of some species almost impossible to place without associated males.

Physical characteristics

Zoraptera are small, elongate insects, ranging from 0.08 to 0.16 in (2–4 mm) in length. All species are similar in appearance and require dissection and microscopic examination for accurate identification. Adults usually are brown but range from pale brown to almost black and typically are not strongly patterned. The nymphs are pale creamy brown. Two distinct body forms occur in both males and females: wingless individuals (by far the more common and frequently encountered form) and winged individuals, which are generally darker and hold the wings flat over the abdomen. Winged individuals can shed their wings like termites and are recognized by the small wing "stubs" that remain.

The hypognathous head, usually narrowed anteriorly, has chewing mouthparts and a pair of antennae with nine segments. Males of many species have a cephalic gland (fontanelle) on the dorsal surface of the head. Mandibles have several "teeth"; maxillary palpi have five segments, and labial palpi have three segments. The well-defined prothorax is more or less square, and the pterothorax is more developed in winged than in wingless forms. The wings are broad and elongate, with reduced venation, and the hind wing is considerably shorter than the forewing and has less venation. Wingless forms lack both compound and simple eyes (ocelli); winged forms have well-developed compound eyes and three simple eyes. The legs are unremarkable other than for the strongly broadened hind femora, which can bear a row of thickened spines. Their number and arrangement are of taxonomic relevance; the tarsi have two segments with two claws. The oval abdomen is somewhat flattened dorsoventrally, and the short, unsegmented cerci (posterior sense organs) usually have a long apical bristle. Female genital structures are simple, with a well-sclerotized internal spermatheca and a long spermathecal duct. Male terminal structures are more complex, often with distinctive genital details. The pattern of thickened bristles on the posterior apex of the abdomen is also distinctive; the most universal male genital feature is a hooklike projection used to link with the female during copulation.

Distribution

The order is distributed widely but predominantly is tropical and subtropical. Zoraptera occur on all continents but have not yet been found on mainland Australia. Their greatest diversity appears to be in the neotropics, with a few species known from North America, Southeast Asia, Africa, or the Pacific islands. Zorotypus hubbardi is widespread in the southeastern United States and ranges northward to beyond forty-one degrees north latitude.

Habitat

Zoraptera are predominantly subcortical and are thus found under the bark of dead and fallen timber. They appear to be most common in rotting wood and logs with loose bark but with the cambium relatively intact. Their presence may help identify a particular phase in wood decomposition. They sometimes occur with termites. Others are found in ground litter, and Z. hubbardi has been reported from piles of decaying sawdust on old milling sites in North America. Winged individuals occasionally are attracted to light or taken in flight interception traps.

Behavior

Zoraptera are gregarious and occur in colonies probably founded by single females. Although winged females have been seen to mate soon after they emerge, no such colony establishment has been noted in the wild. Social structure may be well defined, with formation of dominance hierarchies among males in Z. gurneyi. These hierarchies are determined in part by size and age, with older males becoming more dominant. Aggressive encounters between males of this species involve contact avoidance, head butting, grappling, chasing, and kicking. Grooming behavior, including mutual grooming, is well developed.

Feeding ecology and diet

Zoraptera are primarily fungus feeders, eating both hyphae and spores. Examination of the gut contents of particular species also has revealed arthropod fragments and pieces of wood. Two New World species, Z. barberi and Z. gurneyi, have been observed ingesting small nematodes. Captive zorapterans feed on yeast and crushed rat chow and may engage in cannibalism.

Reproductive biology

Zoraptera usually reproduce sexually. Males of some species are much rarer than the females. The Panamanian Z. gurneyi normally reproduces by parthenogenesis, although mating occurs when males and females meet. Males of Z. gurneyi are larger than females and may fight to gain access to females. The dominance hierarchy of this species may be pronounced and may represent a form of female defense polygyny. Females may mate every few days, either with the same male or with a variety of partners. In contrast, the smaller Z. barberi does not form hierarchies. Courtship involves nuptial feeding, by presentation of a drop of liquid secreted from the opening of the cephalic gland as a courtship gift. In mating of this species, the male is upside down, and copulation lasts for about one minute, occurring after periods of antennation. A single mating pair may copulate several times in succession. There appears to be no well-defined seasonal development in the tropics; eggs take several weeks to hatch. About four or five larval stages (instars) occur; the earlier stages have eight-segmented antennae. Adults may live for about three months.

Conservation status

Most species appear to be rare, with some known from single individuals and localities. Regional or local endemism is common for most species. No formal evaluation of conservation status has been advanced for any member of the order, and no species is listed by the IUCN or in any individual country legislation as having conservation significance. Occasionally, more local concerns (such as for Zorotypus swezeyi in Hawaii) have been expressed because of loss of habitat. No estimates of population size or trends in abundance are available for any species of the order.

Significance to humans

None known.

Species accounts

Resources

Choe, Jae C. "Zoraptera of Panama with a Review of the Morphology, Systematics and Biology of the Order." In Insects of Panama and Mesoamerica: Selected Studies, edited by D. Quintero and A. Aiello. Oxford: Oxford University Press, 1992.

Choe, Jae C. "Courtship, Feeding and Repeated Mating in Zorotypus barberi (Insecta: Zoraptera)." Animal Behaviour 49, no. 6 (1995): 1511–1520.

Gurney, A. B. "A Synopsis of the Order Zoraptera, with Notes on the Biology of Zorotypus hubbardi Caudell." Proceedings of the Entomological Society of Washington 40 (1938): 57–87.

Hubbard, M. D. "A Catalog of the Order Zoraptera (Insecta)." Insecta Mundi 4 (1990): 49–66.

Kukalová-Peck, Jarmila, and Stewart B. Peck. "Zoraptera Wing Structures: Evidence for New Genera and Relationships with the Blattoid Orders (Insecta: Blattoneoptera)." Systematic Entomology 18, no. 4 (1993): 333–350.

New, T. R. "Notes on Neotropical Zoraptera, with Descriptions of Two New Species." Systematic Entomology 3 (1978): 361–370.

[Article by: Timothy R. New]

An order of insects which is related to the termites and psocids. Zoraptera are about 0.08–0.1 in. (2–2.5 mm) long and not important economically. They are of great interest because of their rarity, relatively recent discovery in 1913, and intriguing habits and relationships.

Zoraptera live sheltered from light, in decaying wood, usually in logs and stumps, except during the emergence of winged adults. The winged adults are well pigmented, have eyes, and often shed their wings. In the southeastern United States they occur especially on slabs buried in old sawdust piles. They apparently scavenge, mainly on microscopic molds. Most individuals are of the wingless caste, pale in color, and blind. Metamorphosis is gradual.

Zoraptera are distributed nearly worldwide in warm countries. The best known of the two United States species, Zorothpus hubbardi, occurs from Pennsylvania to Florida, west to Iowa, Kansas, Missouri, and Texas. Approximately 23 species are known; all are in the genus Zorotypus of the family Zorotypidae. See also Insecta.

Zoropterans Fossil range: 145–0 Ma PreЄ Є O S D C P T J K Pg N Cretaceous to Recent
Scientific classification
Kingdom: Animalia Phylum: Arthropoda Subphylum: Hexapoda Class: Insecta Subclass: Pterygota Order: Zoraptera Silvestri, 1913 Family: Zorotypidae Silvestri, 1913 Genus: Zorotypus Silvestri, 1913
Species
See Text

The insect order Zoraptera contains a single family, the Zorotypidae, which in turn contains one extant genus with 34 species, Zorotypus as well as 9 extinct species ^[1].

Contents 1 Phylogeny 2 Description 3 Behavior and ecology 4 Species 5 References 6 General References 7 External links

Phylogeny

The phylogenetic relationship of the order remains controversial and elusive. At present the best supported position based on morphological traits recognizes the Zoraptera as polyneopterous insects related to the webspinners of the Order Embioptera. However, molecular analysis of 18s ribosomal DNA supports a close relationship with the Order Dictyoptera^{[2] [3] [4]}

Description

The name Zoraptera, given by Filippo Silvestri in 1913^[5], is misnamed and potentially misleading: "zor" is Greek for pure and "aptera" means wingless. "Pure wingless" clearly does not fit the winged alate forms, which were discovered several years after the wingless forms had been described.

The members of this order are small insects, 3 millimetres (0.12 in) or less in length, that resemble termites in appearance and in their gregarious behavior. They belong to the hemimetabolous insects. They possess mandibulated biting mouthparts, short cerci (usually 1 segment only), and short antennae with 9 segments. The maxillary palps have five segments, labial palps three, in both the most distal segment is enlarged.

Each species shows polymorphism. Most individuals are the apterous form or "morph", with no wings, no eyes, and no or little pigmentation. A few females and even fewer males are in the alate form with relatively large membranous wings that can be shed at a basal fracture line. Alates also have compound eyes and ocelli, and more pigmentation. This polymorphism can be observed already as two forms of nymphs. Wingspan can be up to 7 millimetres (0.28 in), and the wings can be shed spontaneously. Under good conditions the blind and wingless form predominates, but if their surroundings become too tough, they produce offspring which develop into winged adults with eyes. The wings are paddle shaped, and have reduced venation.

Behavior and ecology

They live in small colonies beneath rotting wood, eating fungal spores and detritus but also can hunt smaller arthropods like mites and collembola. ^[6]

Zorotypus gurneyi lives in colonies consisting of up to several hundred of individuals. Most commonly the colonies have a size is around 30 individuals, of which about 30% are nymphs, the remainder adults.

When two colonies of Z. hubbardi are brought together experimentally, there is no difference in behavior towards members of the own or new colony. Therefore colonies in the wild might merge easily. Winged forms are rare. The males in such average colonies establish a linear dominance hierarchy in which age or duration of colony membership is the prime factor determining dominance. Males appearing later in colonies are at the bottom of the hierarchical ladder, regardless of their body size. By continually attacking other males, the dominant male monopolizes a harem of females. The members of this harem stay clumped together. There is a high correlation between rank and reproductive success of the males. ^{[7] [8]}

Z. barberi lack such a dominance structure but display complex courtship behavior including nuptial feeding. The males possess a cephalic gland that opens in the middle of their head. During courtship they secrete a fluid from this gland and offer it to the female. Acceptance of this droplet by the female acts as behavioral releaser and immediately leads to copulation. ^[6]

Species

34 species are found world-wide, mainly in tropical and subtropical regions around the world. Four species occur north of the Tropic of Cancer, two in the USA and two in Tibet.

Currently there are 34 recognized extant and 9 recognized extinct species.^[1]

Zorotypus acanthothorax Engel & Grimaldi
Zorotypus amazonensis Rafael & Engel
Zorotypus barberi Gurney
Zorotypus brasiliensis Silvestri
Zorotypus buxtoni Karny
Zorotypus caudelli Karny
Zorotypus ceylonicus Silvestri
Zorotypus congensis Ryn-Tournel
Zorotypus cramptoni Gurney
Zorotypus cretatus Engel & Grimaldi
Zorotypus delamarei Paulian
Zorotypus goeleti Engel & Grimaldi
Zorotypus guineensis Silvestri
Zorotypus gurneyi Choe
Zorotypus hamiltoni New
Zorotypus hubbardi Caudell
Zorotypus huxleyi Bolivar & Coronado
Zorotypus javanicus Silvestri
Zorotypus juninensis Engel
Zorotypus lawrencei New
Zorotypus leleupi Weidner
Zorotypus longicercatus Caudell
Zorotypus manni Caudell
Zorotypus medoensis Hwang
Zorotypus mexicanus Bolivar
Zorotypus nascimbenei Engel & Grimaldi
Zorotypus neotropicus Silvestri
Zorotypus newi (Chao & Chen)
Zorotypus philippinensis Gurney
Zorotypus shannoni Gurney
Zorotypus silvestrii Karny
Zorotypus sinensis Hwang
Zorotypus snyderi Caudell
Zorotypus swezeyi Caudell
Zorotypus weidneri New
Zorotypus vinsoni Paulian
Zorotypus zimmermani Gurney

References

1. ^ ^{a b} Rafael JA, Godoi FDP, Engel MS, 2008; "A new species of Zorotypus from eastern Amazonia, Brazil (Zoraptera: Zorotypidae)" Transactions of the Kansas Academy of Science 111:193-202
2. ^ Yoshizawa K 2007; "The Zoraptera problem: evidence for Zoraptera + Embiodea from the wing base." Systematic Entomology 32: 197-204
3. ^ Yoshizawa K & Johnson KP; 2005; "Aligned 18S for Zoraptera (Insecta): Phylogenetic position and molecular evolution." Molecular Phylogenetics and Evolution 37: 572-580
4. ^ Engel MS & Grimaldi DA; 2002; "The first mesozoic Zoraptera (Insecta)." American Museum Novitates 3362:1-20
5. ^ Silvestri, F. (1913); "Descrizione di un nuovo ordine di insetti." Bol. Lab. Zool. Gen. Agric. Portici 7:193–209.
6. ^ ^{a b} Choe JC; 1997; "The evolution of mating systems in the Zoraptera: Mating variations and sexual conflicts." Pages 130-145 in Choe JC & Crespi BJ. (Editors), "The Evolution of Mating Systems in Insects and Arachnids." Cambridge Univ. Press, Cambridge, 575 pp.
7. ^ Choe JC 1994; "Sexual selection and mating system in Zorotypus gurneyi Choe (Insecta, Zoraptera). II Determinants and dynamics of dominance." Behavioral Ecology and Sociobiology 34: 233-237
8. ^ Choe JC 1994; "Sexual selection and mating system in Zorotypus gurneyi Choe (Insecta, Zoraptera ). I Dominance hierarchy and mating success." Behavioral Ecology and Sociobiology 34: 87-93

General References

• Costa JT 2006 Psocopera and Zoraptera. In: Costa JT The other Insect Societies. The Belknap Press of Harvard University Press, Cambridge, MA and London, UK pp 193-211
• Grimaldi, D. and Engel, M.S. (2005). Evolution of the Insects. Cambridge University Press. ISBN 0-521-82149-5. 
• Rafael, J.A. & M.S. Engel (2006) A new species of Zorotypus from Central Amazonia, Brazil (Zoraptera: Zorotypidae). American Museum Novitates 3528: 1-11.

External links

• Tree of Life Zoraptera
• Zoraptera database

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