Scutelleridae is a family of true bugs. They are commonly known as jewel (stink) bugs or metallic shield bugs due to their often unique coloration. With the name based on the Asian genus Scutellera, 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 rather than a bug. These insects use their piercing-sucking mouthparts to 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 worldwide.

Description

Jewel bugs are small to medium-sized, oval-shaped bugs with a body length averaging . They can easily be distinguished from stink bugs (Pentatomidae) because the shield-like enlarged last section of their thorax (known as the scutellum, Latin for "little shield") completely covers the abdomen and the wings.

Despite their resemblance to beetles, jewel bugs are hemipterans, or true bugs. The scutellum extends the thorax, unlike the elytra of beetles, which are hardened forewings. As such, jewel bugs have four membranous wings underneath the scutellum in contrast to two in beetles. Like all heteropterans, jewel bugs are characterized by a segmented beak-like mouthpart (known as the rostrum). The tarsus has three segments (tarsomeres). the most conspicuous jewel bugs are often uniquely colored, exhibiting a wide range of iridescent metallic hues that change with the viewing angle. The colors result from 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 surface with water.

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 instars and even within adults of a species.

Jewel bugs are also known to mimic the colors, patterns, and shapes of other organisms for defensive purposes. An example is the yellow-spotted black Steganocerus multipunctatus which exhibits Müllerian mimicry with the tortoise beetle Chiridopsis suffriani.

Ecology and life cycle

All jewel bugs feed on plants (phytophagous). 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 embryo. 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) exits 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 (hemimetaboly) and do not possess larval and pupal stages. Instead, the adults develop from several stages of nymphs through successive moltings. Nymphs resemble the adults except for size and the absence of wings. They can be of different coloration or patterns from adults. Pachycoris klugii, Pachycoris stalii, Pachycoris torridus, and Tectocoris diophthalmus.

<gallery widths="200px" heights="200px">

File:アカギカメムシ 卵の保護 大和村 奄美大島.jpg|A female of Cantao ocellatus protecting a cluster of eggs.

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. 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, in the foreground are two nymphs.

File:Scutelleridae cropped 2.jpg|A jewel bug from the Philippines feeding on Jatropha.

File:ラデンキンカメムシｰアカギの葉に群れる。奄美大島.jpg|Scutellera amethystina, congregating on Bischofia javanica.

File:ナナホシキンカメムシ Calliphara excellens 交尾 沖縄島 2017-5-06.jpg|Calliphara excellens copulating.

</gallery>

Reproduction

Chemical secretions from dorsal, abdominal, or sternal exocrine glands are used to attract mates by certain species of jewel bugs. In certain genera (like Tectocoris, Psacasta, Odontoscelis, and Irochrotus), males possess special unicellular glands in the abdomen known as the androconia. They release sex pheromones when ruptured.

Defenses

Like stink bugs, a vast majority of jewel bugs, both adults and nymphs, can release pungent defensive chemicals from glands on the sides of the thorax. Typical compounds exuded by jewel bugs include alcohols, aldehydes, and esters.

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. It belongs to the order Hemiptera (true bugs), under the suborder Heteroptera and infraorder Pentatomomorpha. They are classified under the superfamily Pentatomoidea. They were formerly classified as a subfamily of Pentatomidae 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. Below is the morphological unweighted tree of the superfamily Pentatomoidea after Grazia et al. (2008).

Elvisurinae

Auth.: Stål, 1872. Widespread distribution, with the type genus Elvisura found in southern Africa; only one species of Elvisurinae, Solenosthedium bilunatum, is found in Europe.

  1. Austrotichus - monotypic A. rugosus
  2. Coleotichus
  3. Elvisura
  4. Solenosthedium
  5. Solenotichus

Eurygastrinae

Auth.: Amyot & Audinet-Serville, 1843

;Tribe Eurygastrini Amyot & Audinet-Serville, 1843

  1. Eurygaster
  2. Polyphyma

;Tribe Psacastini Mulsant & Rey, 1865

  1. Ceratocranum
  2. Periphima
  3. Periphymopsis
  4. Promecocoris
  5. Psacasta
  6. Xerobia

Hoteinae

Auth.: Carapezza, 2008

  1. Deroplax
  2. Ellipsocoris
  3. Hotea

Odontoscelinae

Auth.: Amyot & Audinet-Serville, 1843; mostly European

  1. Holonotellus
  2. Irochrotus
  3. Odontoscelis

Odontotarsinae

Auth.: Mulsant & Rey, 1865

;Tribe Odontotarsini Mulsant & Rey, 1865

  1. Ahmadocoris
  2. Alphocoris
  3. Melanodema
  4. Odontotarsiellus
  5. Odontotarsus
  6. Urothyreus

;Tribe Phimoderini Fuente, 1974

  1. Euptychodera
  2. Fokkeria
  3. Morbora
  4. Phimodera
  5. Vanduzeeina

Pachycorinae

Auth.: Amyot & Audinet-Serville, 1843

  1. Acantholomidea
  2. Agonosoma
  3. Ascanius (bug)
  4. Brailovskylus
  5. Camirus
  6. Chelycoris
  7. Chelyschema
  8. Coptochilus
  9. Crathis (bug)
  10. Diolcus
  11. Dystus
  12. Ephynes
  13. Galeacius
  14. Homaemus
  15. Lobothyreus
  16. Misippus
  17. Nesogenes
  18. Orsilochides
  19. Pachycoris
  20. Polytes
  21. Sphyrocoris
  22. Stethaulax
  23. Symphylus
  24. Testrina
  25. Tetyra
  26. Tiridates (bug)

Scutellerinae

Auth.: Leach, 1815.

Selected genera:

  • Augocoris
  • Calliphara
  • Cantao
  • Chrysocoris
  • Eucorysses Amyot & Audinet-Serville, 1843
  • Lampromicra
  • Scutellera Lamarck, 1801
  • 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 pests. Some of the most economically impactful species are members of the genus Eurygaster. Together with some species of stink bugs, they are collectively known as sunn pests or wheat bugs.

Eurygaster integriceps, in particular, is a very destructive pest of cereal crops in North Africa, the Balkans, and western and central Asia. 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 wasps of the family Scelionidae from the genera Trissolcus and Ooencyrtus.

The cotton harlequin bug (Tectocoris diophthalmus) is also an important pest of cotton crops and Hibiscus.

Conservation

Biological methods of pest control have sometimes backfired. A parasitoid fly which preys on hemipterans, Trichopoda pennipes, was introduced to Hawaii to control the invasive species Nezara viridula, the southern green stink bug. The fly now threatens native species 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 widths="200px" heights="160px">

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)

</gallery>

See also

  • Sunn pest

References

  • A gallery of Scutellerid photos from Flickr