Scutelleridae is a

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

true bugs Hemiptera (; ) is an order (biology), order of insects, commonly called true bugs, comprising over 80,000 species within groups such as the cicadas, aphids, planthoppers, leafhoppers, Reduviidae, assassin bugs, Cimex, bed bugs, and shield bugs. ...

. They are commonly known as jewel bugs or metallic shield bugs due to their often brilliant coloration. They are also known as shield-backed bugs due to the enlargement of the thoracic scutellum into a continuous shield over the abdomen and wings. This latter characteristic distinguishes them from most other families within Heteroptera, and may lead to misidentification as a

beetle Beetles are insects that form the order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 describ ...

rather than a bug. These insects feed on plant juices from a variety of different species, including some commercial crops. Closely related to stink bugs, they may also produce an offensive odour when disturbed. There are around 450

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

worldwide.

Description

Jewel bugs are small to medium-sized oval-shaped bugs with a body length averaging at . They can easily be distinguished from stink bugs (

Pentatomidae Pentatomidae is a family of insects belonging to the order Hemiptera, generally called shield bugs or stink bugs. Pentatomidae is the largest family in the superfamily Pentatomoidea, and contains around 900 genera and over 4700 species.Robert ...

) because the shield-like enlarged last section of their

thorax The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the cre ...

(known as the scutellum,

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

for "little shield") completely covers the

abdomen The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the to ...

and the wings. Despite their resemblance to beetles, jewel bugs are hemipterans or true bugs. The scutellum is an extension of the thorax, unlike the

elytra An elytron (; ; , ) is a modified, hardened forewing of beetles (Coleoptera), though a few of the true bugs (Hemiptera) such as the family Schizopteridae are extremely similar; in true bugs, the forewings are called hemelytra (sometimes alterna ...

of beetles which are hardened forewings. As such, jewel bugs have four membranous wings underneath the scutellum in contrast to two in beetles. The scutellum in jewel bugs also does not have a division in the middle and thus does not 'split open' when they take flight like in beetles. The heads of jewel bugs are triangular and the antennae have three to five segments. Like all heteropterans, jewel bugs are characterized by a segmented beak-like mouthpart (known as the rostrum). During feeding, jewel bugs inject proteolytic enzymes in their saliva into plants, digesting plant matter into a liquid form which they then suck up. The tarsus has three segments (tarsomeres). File:Shield-backed bug (Graptocoris aulicus) nymph.jpg, Shield-backed bug (''Graptocoris aulicus'') nymph,

Uganda }), is a landlocked country in East Africa. The country is bordered to the east by Kenya, to the north by South Sudan, to the west by the Democratic Republic of the Congo, to the south-west by Rwanda, and to the south by Tanzania. The sou ...

File:Chrysocoris, Hebbal, Bangalore, India - 20060806.jpg, alt=Chrysocoris sp. from India, perched on some leaves., '' Chrysocoris'' sp., an iridescent green jewel bug from

India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...

. File:Giant jewel bug (Eucorysses grandis).jpg, alt=Eucorysses grandis from Japan, crawling up on a wall., A brilliant orange, red, and black giant jewel stink bug '' Eucorysses grandis'', from Japan. The pattern and coloration of this species can often vary from pale cream to deep red.

Colors

Though some species are quite drab, the most conspicuous jewel bugs are often brilliantly colored, exhibiting a wide range of iridescent metallic hues that change with the view angle. The colors are the result of a combination of factors. Some species like '' Chrysocoris stockerus'' and '' Scutellera nobilis'' display colors from multiple thin layers of pigmented chitin. The colors often change or become duller when the specimens are dried, due to the topmost chitinous layer becoming opaque and obscuring the colors of the bottom layer. The colors can be restored by moistening the surfaces with water. Iridescence (or goniochromism) in jewel bugs like '' Poecilocoris lewisi'' are the result of

structural coloration Structural coloration in animals, and a few plants, is the production of colour by microscopically structured surfaces fine enough to interfere with visible light instead of pigments, although some structural coloration occurs in combination wi ...

. Instead of pigments, the colors are caused by the interference, diffraction, or scattering of light by numerous tiny structures. In ''Poecilocoris lewisi'', multiple tiny conical protuberances around 900 nm in height and averaging at a diameter of 360 nm are scattered on the

epicuticle The cuticle forms the major part of the integument of the Arthropoda. It includes most of the material of the exoskeleton of the insects, Crustacea, Arachnida, and Myriapoda. Morphology In arthropods, the integument, the external "skin", or ...

. These structures affect light passing through them, producing their oily-looking blue sheen (known as the Tyndall effect or

Mie scattering The Mie solution to Maxwell's equations (also known as the Lorenz–Mie solution, the Lorenz–Mie–Debye solution or Mie scattering) describes the scattering of an electromagnetic plane wave by a homogeneous sphere. The solution takes the ...

). In other species like the African shield bug ('' Calidea panaethiopica''), the dorsal cuticle is dotted with tiny regularly spaced hemispherical cavities. The depressions act like Bragg mirrors. When light hits the pitted surface, it gives off multiple reflections resulting in the distinctive two tone yellow-blue iridescence. The colors and patterns on jewel bugs can vary significantly between

instar An instar (, from the Latin '' īnstar'', "form", "likeness") is a developmental stage of arthropods, such as insects, between each moult (''ecdysis''), until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or ...

s and even within adults of a species. Jewel bugs are also known to

mimic MIMIC, known in capitalized form only, is a former simulation computer language developed 1964 by H. E. Petersen, F. J. Sansom and L. M. Warshawsky of Systems Engineering Group within the Air Force Materiel Command at the Wright-Patterson AFB in ...

the colors, patterns, and shape of other organisms for defensive purposes. An example is the yellow-spotted black '' Steganocerus multipunctatus'' which exhibits

Müllerian mimicry Müllerian mimicry is a natural phenomenon in which two or more well-defended species, often foul-tasting and sharing common predators, have come to mimic each other's honest warning signals, to their mutual benefit. The benefit to Mülleria ...

with the

tortoise beetle The Cassidinae (tortoise and leaf-mining beetles) are a subfamily of the leaf beetles, or Chrysomelidae. The antennae arise close to each other and some members have the pronotal and elytral edges extended to the side and covering the legs so as ...

'' Chiridopsis suffriani''.

Ecology and life cycle

All jewel bugs feed on

plants Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclude ...

(

phytophagous A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpar ...

). The eggs are laid in compact clusters. They may be round or barrel-shaped with a lid or a cap at the top (known as the operculum). They also contain a ring of small protuberances near the cap called micropylar processes. They permit the passage of sperm into the egg for fertilization and enable gaseous exchange from within the egg and the outside world for the embryos. The eggs are white or cream colored when freshly laid but can change color as the embryo matures. When hatching, the prolarva (the advanced embryo) exit the egg by opening the lid through peristaltic movements and with the help of a T-shaped internal structure in the egg (known as the egg burster). Like all hemipterans, jewel bugs undergo

incomplete metamorphosis Hemimetabolism or hemimetaboly, also called incomplete metamorphosis and paurometabolism,McGavin, George C. ''Essential Entomology: An Order-by-Order Introduction''. Oxford: Oxford University Press, 2001. pp. 20. is the mode of development of certa ...

(hemimetaboly) and do not possess

larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. ...

l and

pupa A pupa ( la, pupa, "doll"; plural: ''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 thei ...

l stages. Instead the adults develop from several stages (

s) of

nymphs A nymph ( grc, νύμφη, nýmphē, el, script=Latn, nímfi, label=Modern Greek; , ) in ancient Greek folklore is a minor female nature deity. Different from Greek goddesses, nymphs are generally regarded as personifications of nature, are ...

(usually five) through successive moltings ( ecdysis). Nymphs resemble the adults except for size and the absence of wings. They can be of different coloration or patterns from adults. Some species are known to exhibit

parental care Parental care is a behavioural and evolutionary strategy adopted by some animals, involving a parental investment being made to the evolutionary fitness of offspring. Patterns of parental care are widespread and highly diverse across the animal ki ...

of eggs and

nymph A nymph ( grc, νύμφη, nýmphē, el, script=Latn, nímfi, label= Modern Greek; , ) in ancient Greek folklore is a minor female nature deity. Different from Greek goddesses, nymphs are generally regarded as personifications of nature, are ...

s. Notable examples of which are '' Cantao parentum'', '' Pachycoris klugii'', '' Pachycoris stalii'', '' Pachycoris torridus'', and '' Tectocoris diophthalmus''. File:Koa bug eggs.jpg, alt=A cluster of empty barrel shaped eggs on a leaf., A cluster of the empty barrel-shaped eggs of the Koa bug (''Coleotichus blackburniae'') from

Hawaii Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only state ...

. The 'lids' can clearly be seen. File:Pachycoris torridus 003.jpg, alt=A jewel bug emerging from its old exoskeleton while two nymphs look on in the foreground., A jewel bug molting (ecdysis). The pale-colored adult is emerging from its old

exoskeleton An exoskeleton (from Greek ''éxō'' "outer" and ''skeletós'' "skeleton") is an external skeleton that supports and protects an animal's body, in contrast to an internal skeleton (endoskeleton) in for example, a human. In usage, some of the ...

, in the foreground are two

. File:Scutelleridae cropped 2.jpg, A jewel bug from the

Philippines The Philippines (; fil, Pilipinas, links=no), officially the Republic of the Philippines ( fil, Republika ng Pilipinas, links=no), * bik, Republika kan Filipinas * ceb, Republika sa Pilipinas * cbk, República de Filipinas * hil, Republ ...

feeding on ''

Jatropha ''Jatropha'' is a genus of flowering plants in the spurge family, Euphorbiaceae. The name is derived from the Greek words ἰατρός (''iatros''), meaning "physician", and τροφή (''trophe''), meaning "nutrition", hence the common name ...

''. File:Calliphara exellens (Burmeister, 1834).jpg, '' Calliphara excellens'' from Japan.

Reproduction

Chemical secretions from dorsal abdominal or sternal

exocrine gland Exocrine glands are glands that secrete substances on to an epithelial surface by way of a duct. Examples of exocrine glands include sweat, salivary, mammary, ceruminous, lacrimal, sebaceous, prostate and mucous. Exocrine glands are one of ...

s are used to attract mates by certain species of jewel bugs. In certain genera (like '' Tectocoris'', '' Psacasta'', '' Odontoscelis'', and '' Irochrotus''), males possess special

unicellular A unicellular organism, also known as a single-celled organism, is an organism that consists of a single cell, unlike a multicellular organism that consists of multiple cells. Organisms fall into two general categories: prokaryotic organisms and ...

glands in the abdomen known as the androconia (singular: androconium). They release sex pheromones when ruptured. Females possess a

spermatheca The spermatheca (pronounced plural: spermathecae ), also called receptaculum seminis (plural: receptacula seminis), is an organ of the female reproductive tract in insects, e.g. ants, bees, some molluscs, oligochaeta worms and certain other in ...

, an ectodermal gland which opens into the

oviduct The oviduct in mammals, is the passageway from an ovary. In human females this is more usually known as the Fallopian tube or uterine tube. The eggs travel along the oviduct. These eggs will either be fertilized by spermatozoa to become a zygote, o ...

. These serve as storage for sperm deposited by males. It contains glands which can nourish the

spermatozoa A spermatozoon (; also spelled spermatozoön; ; ) is a motile sperm cell, or moving form of the haploid cell that is the male gamete. A spermatozoon joins an ovum to form a zygote. (A zygote is a single cell, with a complete set of chromos ...

until they can be released to fertilize eggs. Male jewel bugs of the genus '' Hotea'' possess an unusually large, spiky, and heavily sclerotized genitalia. They are used in a mating practice known as

traumatic insemination Traumatic insemination, also known as hypodermic insemination, is the mating practice in some species of invertebrates in which the male pierces the female's abdomen with his aedeagus and injects his sperm through the wound into her abdominal cav ...

, a result of evolutionary sexual conflict. Male ''Hotea'' bugs tear through the female reproductive ducts to deposit sperm, inflicting substantial damage to the female in the process.

Defenses

Like stink bugs, a vast majority of jewel bugs, both adults and nymphs, are also capable of releasing pungent defensive chemicals from glands located on the sides of the thorax. Typical compounds exuded by jewel bugs include alcohols,

aldehyde In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl grou ...

s, and

ester In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides a ...

s. Nymphs and adults often exhibit clustering behavior, being found in large numbers close to each other. This behavior is thought to have an evolutionary advantage. The more individuals present in an area, the stronger the odor of the chemicals released when the bugs are threatened. If this fails, stink bugs will react to threat by flying away or dropping to the ground.

Classification and evolution

Scutellerids were first described by the English

zoologist Zoology ()The pronunciation of zoology as is usually regarded as nonstandard, though it is not uncommon. is the branch of biology that studies the animal kingdom, including the structure, embryology, evolution, classification, habits, and d ...

William Elford Leach William Elford Leach FRS (2 February 1791 – 25 August 1836) was an English zoologist and marine biologist. Life and work Elford Leach was born at Hoe Gate, Plymouth, the son of an attorney. At the age of twelve he began a medical appre ...

in 1815. It belongs to the order Hemiptera (true bugs), under the suborder Heteroptera and

infraorder Order ( la, ordo) is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and ...

Pentatomomorpha The Pentatomomorpha comprise an infraorder of insects in the true bug order Hemiptera. It unites such animals as the stink bugs (Pentatomidae), flat bugs (Aradidae), seed bugs (Lygaeidae and Rhyparochromidae), etc. They are closely related to ...

. They are classified under the superfamily

Pentatomoidea The Pentatomoidea are a superfamily of insects in the Heteroptera suborder of the Hemiptera order. As Hemiptera, they share a common arrangement of sucking mouthparts. The roughly 7000 species under Pentatomoidea are divided into 21 families (16 ...

. They were formerly classified as a subfamily of

by George Willis Kirkaldy in 1909. The earliest attempt to restore them to family status was in 1917 by Edward Payson Van Duzee. Most authorities today regard it as a valid family group. In

phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

studies in 2008 by Grazia ''et al.'', Scutelleridae was shown to be consistently monophyletic, basal to Acanthosomatidae, and distal to Plataspididae and Parastrachiidae. Below is the morphological unweighted tree of the superfamily

after Grazia ''et al.'' (2008).

Subfamilies and genera

The family is composed of about 81 genera and around 450 species worldwide. While the

tribal The term tribe is used in many different contexts to refer to a category of human social group. The predominant worldwide usage of the term in English is in the discipline of anthropology. This definition is contested, in part due to conflic ...

and subfamilial classifications remain unclear, they are divided into eight subfamilies ''

sensu lato ''Sensu'' is a Latin word meaning "in the sense of". It is used in a number of fields including biology, geology, linguistics, semiotics, and law. Commonly it refers to how strictly or loosely an expression is used in describing any particular c ...

'': Elvisurinae, Eurygastrinae, Hoteinae (sometimes classified under Pachycorinae), Odontoscelinae, Odontotarsinae, Pachycorinae, Scutellerinae, and Tectocorinae.Biolib
/ref> * Elvisurinae **'' Austrotichus'' Gross, 1975 **'' Coleotichus'' White, 1839 **'' Elvisura'' Spinola, 1837 **'' Solenosthedium'' Spinola, 1837 **'' Solenotichus'' Martin, 1897 * Eurygastrinae Amyot & Audinet-Serville, 1843 **'' Euptychodera'' **'' Eurygaster'' Laporte de Castelnau, 1833 **'' Fokkeria'' **'' Phimodera'' **'' Vanduzeeina'' * Hoteinae **'' Deroplax'' Mayr, 1864 **'' Ellipsocoris'' Mayr, 1864 **'' Hotea'' Amyot & Serville, 1843 * Odontotarsinae Mulsant & Rey, 1865 **'' Ahmadocoris'' Carapezza, 2009 **'' Alphocoris'' Germar, 1830 **'' Melanodema'' Jakovlev, 1880 **'' Odontotarsiellus'' Hoberlandt, 1955 **'' Odontotarsus'' Laporte, 1833 **'' Urothyreus'' Horváth, 1921 * Pachycorinae Amyot & Audinet-Serville, 1843 **'' Acantholomidea'' **''

Camirus Camirus or Kamiros ( grc, Κάμιρος; ) or Cameirus or Kameiros (Κάμειρος) was a city of ancient Rhodes, in the Dodecanese, Greece. Its site is on the northwest coast of the island, west of the modern village of Kalavarda. History ...

'' **'' Diolcus'' **'' Homaemus'' **'' Orsilochides'' **'' Pachycoris'' **'' Sphyrocoris'' **'' Stethaulax'' **'' Symphylus'' **'' Tetyra'' * Scutellerinae Leach, 1815 **'' Augocoris'' **'' Calliphara'' **'' Cantao'' **'' Chrysocoris'' **'' Lampromicra'' **'' Sphaerocoris'' * Tectocorinae McDonald & Cassis, 1984 (monotypic) **'' Tectocoris'' Hahn, 1834

Economic significance

Though most jewel bugs do little harm to crop plants, a few members of Scutelleridae are considered major

agricultural pest A pest is any animal or plant harmful to humans or human concerns. The term is particularly used for creatures that damage crops, livestock, and forestry or cause a nuisance to people, especially in their homes. Humans have modified the environ ...

s. Together with some species of stink bugs, they are collectively known as sunn pests (also spelled as senn, , or shüne pests) or wheat bugs. The most economically important species of which are members of the genus '' Eurygaster''. '' Eurygaster integriceps'', in particular, is a very destructive pest of cereal crops in

North Africa North Africa, or Northern Africa is a region encompassing the northern portion of the African continent. There is no singularly accepted scope for the region, and it is sometimes defined as stretching from the Atlantic shores of Mauritania in ...

, the

Balkans The Balkans ( ), also known as the Balkan Peninsula, is a geographical area in southeastern Europe with various geographical and historical definitions. The region takes its name from the Balkan Mountains that stretch throughout the who ...

, and western and central

Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an are ...

. Other scutellerids known under the name 'sunn pest' include members of the genus '' Odontotarsus'', among others. Methods of control for sunn pests have included biological pest control, using

wasp A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder. ...

s of the family Scelionidae from the genera '' Trissolcus'' and '' Ooencyrtus''. The cotton harlequin bug ('' Tectocoris diophthalmus'') is also an important pest of

cotton Cotton is a soft, fluffy staple fiber that grows in a boll, or protective case, around the seeds of the cotton plants of the genus '' Gossypium'' in the mallow family Malvaceae. The fiber is almost pure cellulose, and can contain minor pe ...

crops and ''

Hibiscus ''Hibiscus'' is a genus of flowering plants in the mallow family, Malvaceae. The genus is quite large, comprising several hundred species that are native to warm temperate, subtropical and tropical regions throughout the world. Member species ...

''.

Conservation

Biological methods of pest control have sometimes backfired. A parasitoid fly which preys on hemipterans, '' Trichopoda pennipes'' was introduced to

to control the invasive species ''

Nezara viridula ''Nezara viridula'', commonly known as the southern green stink bug (USA), southern green shield bug (UK) or green vegetable bug (Australia and New Zealand), is a plant-feeding stink bug. Believed to have originated in Ethiopia, it can now be fo ...

'', the southern green stink bug. The fly now threatens

native species In biogeography, a native species is indigenous to a given region or ecosystem if its presence in that region is the result of only local natural evolution (though often popularised as "with no human intervention") during history. The term is equ ...

of bugs in Hawaii as well, particularly the Koa bug (''Coleotichus blackburniae'', a jewel bug species notable for not possessing stink glands) which has now become rare.

Gallery

File:Molting Jewel Bug 01.jpg, Molting (moulting) jewel bug (1) File:Molting Jewel Bug 02.jpg, Molting (moulting) jewel bug (2) File:Molting Jewel Bug 03.jpg, Molting (moulting) jewel bug (3) File:Molting Jewel Bug 04.jpg, Molting (moulting) jewel bug (4)

References

External links

A gallery of Scutellerid photos from Flickr
{{Taxonbar, from=Q642857 Agricultural pest insects Heteroptera families Shield bugs Taxa named by William Elford Leach