Sweetpotato bug
Encyclopedia
The sweetpotato bug is a species of insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...

 in the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 Coreidae
Coreidae
Coreidae are a large family of predominantly herbivorous insects that belong in the hemipteran suborder Heteroptera. There are more than 1,800 species in over 250 genera. They vary in size from 7 to 45 mm, making the larger species some of the biggest heteropterans. The body shape of coreids...

. Native to Southeast Asia
Southeast Asia
Southeast Asia, South-East Asia, South East Asia or Southeastern Asia is a subregion of Asia, consisting of the countries that are geographically south of China, east of India, west of New Guinea and north of Australia. The region lies on the intersection of geological plates, with heavy seismic...

, the species has immigrated to the Pacific Islands
Pacific Islands
The Pacific Islands comprise 20,000 to 30,000 islands in the Pacific Ocean. The islands are also sometimes collectively called Oceania, although Oceania is sometimes defined as also including Australasia and the Malay Archipelago....

. Frequently laying its eggs on the same Leguminosae and Convolvulaceae
Convolvulaceae
Convolvulaceae, known commonly as the bindweed or morning glory family, are a group of about 60 genera and more than 1,650 species of mostly herbaceous vines, but also trees, shrubs and herbs.- Description :...

 plants on which it feeds, the female of P. grossipes is very protective of her young, notably guarding both eggs and nymphs
Nymph (biology)
In biology, a nymph is the immature form of some invertebrates, particularly insects, which undergoes gradual metamorphosis before reaching its adult stage. Unlike a typical larva, a nymph's overall form already resembles that of the adult. In addition, while a nymph moults it never enters a...

 from predators.

Distribution

Native to Southeast Asia
Southeast Asia
Southeast Asia, South-East Asia, South East Asia or Southeastern Asia is a subregion of Asia, consisting of the countries that are geographically south of China, east of India, west of New Guinea and north of Australia. The region lies on the intersection of geological plates, with heavy seismic...

, the species' distribution ranges from Indonesia
Indonesia
Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...

, throughout Peninsular Malaysia
Peninsular Malaysia
Peninsular Malaysia , also known as West Malaysia , is the part of Malaysia which lies on the Malay Peninsula. Its area is . It shares a land border with Thailand in the north. To the south is the island of Singapore. Across the Strait of Malacca to the west lies the island of Sumatra...

 and India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

. The species has migrated to other areas, including Guam
Guam
Guam is an organized, unincorporated territory of the United States located in the western Pacific Ocean. It is one of five U.S. territories with an established civilian government. Guam is listed as one of 16 Non-Self-Governing Territories by the Special Committee on Decolonization of the United...

 and Hawaii
Hawaii
Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...

.

Description

Brown in color with black legs, individuals grow to be about 2 centimetre (0.78740157480315 in) long. Like other Coreidae, P. grossipes is oval-shaped with segmented antennae, a numerously veined forewing membrane, a metathoracic stink gland and enlarged hind tibia.

Feeding

The insect feeds on Leguminosae and Convolvulaceae
Convolvulaceae
Convolvulaceae, known commonly as the bindweed or morning glory family, are a group of about 60 genera and more than 1,650 species of mostly herbaceous vines, but also trees, shrubs and herbs.- Description :...

 plants. In addition to the sweet potato
Sweet potato
The sweet potato is a dicotyledonous plant that belongs to the family Convolvulaceae. Its large, starchy, sweet-tasting, tuberous roots are an important root vegetable. The young leaves and shoots are sometimes eaten as greens. Of the approximately 50 genera and more than 1,000 species of...

 from which it derives its common name, it frequents other plants of the Ipomoea
Ipomoea
Ipomoea is the largest genus in the flowering plant family Convolvulaceae, with over 500 species. Most of these are called "morning glories", but this can refer to related genera also. Those formerly separated in Calonyction are called "moonflowers"...

genus as well as catjang
Catjang
Catjang is a subspecies of cowpea. The catjang plant is native to Africa, and is an erect densely branched shrubby perennial of Old World tropics. It now grows in other warm regions, as well...

, Clitoria ternatea
Clitoria ternatea
Clitoria ternatea is a plant species belonging to the Fabaceae family.- Distribution :This plant is native to tropical equatorial Asia, but has been introduced to Africa, Australia and America....

and the common bean
Common bean
Phaseolus vulgaris, the common bean, is an herbaceous annual plant domesticated independently in ancient Mesoamerica and the Andes, and now grown worldwide for its edible bean, popular both dry and as a green bean. The leaf is occasionally used as a leaf vegetable, and the straw is used for fodder...

. Since the removal of juice from the stem in the insect's feeding causes the plant to wither and disrupts its production of fruit
Fruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...

, P. grossipes has been regarded as a pest.

Biology

Physomerus grossipes oviposits
Oviposition
Oviposition is the process of laying eggs by oviparous animals.Some arthropods, for example, lay their eggs with an organ called the ovipositor.Fish , amphibians, reptiles, birds and monetremata also lay eggs....

 its eggs on the undersides of leaves or on the stems of the plants on which it feeds as well as on neighboring sedges
Cyperaceae
Cyperaceae are a family of monocotyledonous graminoid flowering plants known as sedges, which superficially resemble grasses or rushes. The family is large, with some 5,500 species described in about 109 genera. These species are widely distributed, with the centers of diversity for the group...

. A 1990 study found a mean clutch size of 83 eggs, although some egg deposits numbering twice that have been found, possibly representing the collected eggs of several insects. The female of P. grossipes is very protective, providing the "best known example" of "maternal care in the large family Coreidae." Mothers guard their eggs, threatening and occasionally even rushing at the predators that approach them. In addition, P. grossipes generates a strong-smelling fluid from a metathoracic gland with which the mother sprays larger predators through the anal orifice.

In spite of this protection, approximately 20% of the eggs are eaten by predators such as ants and 13% are lost to parasitoid
Parasitoid
A parasitoid is an organism that spends a significant portion of its life history attached to or within a single host organism in a relationship that is in essence parasitic; unlike a true parasite, however, it ultimately sterilises or kills, and sometimes consumes, the host...

 predation by chalcid wasp
Chalcid wasp
Chalcid wasps belong to the insect order Hymenoptera, and are one of the largest groups within the order, with some 22,000 known species, and an estimated total diversity of anywhere from 60,000 to more than 500,000 species, meaning the vast majority have yet to be discovered and described.Most of...

s, which lay their eggs within the eggs of P. grossipes. Losses to unguarded clutches are much higher. The surviving eggs hatch in approximately 15 days. The insect goes through five nymphal stages ranging from 85 days for males to 88 days for females before reaching full maturity.

After the eggs are hatched, the mother remains to guard the gregarious nymphs, feeding them predigested food. Mixed-age nymph groups have been observed, and there have also been several documented cases of multiple females guarding one nymph group. Rare enough that this may be an aberration, the phenomenon may also suggest still undisclosed social dimensions to P. grossipes, particularly in conjunction with collective egg clutches. It is possible that two mothers are cooperating to guard their broods or that an unmated female may assist to raise a brood that is not hers. Males have frequently been found near nymph groups and may also be present to supply protection to the brood.
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