''Spilostethus rivularis'', the rivulet milkweed bug, is a species of bug belonging to the family

Lygaeidae The Lygaeidae are a family in the Hemiptera (true bugs), with more than 110 genera in four subfamilies. The family is commonly referred to as seed bugs, and less commonly, milkweed bugs, or ground bugs. However, while many of the species feed on ...

sensu stricto ''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 co ...

'', and subfamily

Lygaeinae Lygaeinae is a subfamily of ground bugs in the insect family Lygaeidae. Genera Genera within this subfamily include: : '' Achlyosomus'' Slater Alex, 1992 : '' Acrobrachys'' Horvath, 1914 : '' Acroleucus'' Stal, 1874 : '' Aethalotus'' Stal, 1874 ...

. It is widely distributed in Africa, where it is found commonly in grassland, savannah grassland or croplands.

Description

The egg and instars were described by Slater and Perry (1973). The nymph is conspicuously coloured yellow-orange to orange, and striped with brown. Adults measure about 13 mm in length, and are conspicuously barred rufous and greyish black on the head,

pronotum The prothorax is the foremost of the three segments in the thorax of an insect, and bears the first pair of legs. Its principal sclerites (exoskeletal plates) are the pronotum (dorsal), the prosternum (ventral), and the propleuron (lateral) on ea ...

and hard parts (i.e. clavus and corium) of the

hemelytra 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 ...

. The scutellum is blackish and the membranes of the hemelytra are chestnut brown. left, 200px, Adult feeding on '' Ozoroa'' nectar

Biology

Members of its genus feed on the seeds of various

milkweed ''Asclepias'' is a genus of herbaceous, perennial, flowering plants known as milkweeds, named for their latex, a milky substance containing cardiac glycosides termed cardenolides, exuded where cells are damaged. Most species are toxic to humans ...

species, related ''

Calotropis ''Calotropis'' is a genus of flowering plants in the family Apocynaceae, first described as a genus in 1810. It is native to southern Asia and North Africa. They are commonly known as milkweeds because of the latex they produce. ''Calotropis'' ...

'' spp., and

afrotropical The Afrotropical realm is one of Earth's eight biogeographic realms. It includes Africa south of the Sahara Desert, the majority of the Arabian Peninsula, the island of Madagascar, southern Iran and extreme southwestern Pakistan, and the island ...

Solanum ''Solanum'' is a large and diverse genus of flowering plants, which include three food crops of high economic importance: the potato, the tomato and the eggplant (aubergine, brinjal). It is the largest genus in the nightshade family Solanaceae ...

'' spp. They may also be found on the flower heads of various

composite Composite or compositing may refer to: Materials * Composite material, a material that is made from several different substances ** Metal matrix composite, composed of metal and other parts ** Cermet, a composite of ceramic and metallic materials ...

plants, and ''S. rivularis'' has been noted to congregate on ''

Lopholaena coriifolia ''Lopholaena'' (from ''lophos'', a crest, and ''chlaina'', a cloak) is a genus of perennial shrubs and herbaceous plants in the family Asteraceae. About 20 species occur from tropical to southern Africa. Description The flower head A pseudant ...

'' in

South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring countri ...

. The present species has been recorded on

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 perce ...

and

sorghum ''Sorghum'' () is a genus of about 25 species of flowering plants in the grass family (Poaceae). Some of these species are grown as cereals for human consumption and some in pastures for animals. One species is grown for grain, while many othe ...

(nymphs and adults) in

Nigeria Nigeria ( ), , ig, Naìjíríyà, yo, Nàìjíríà, pcm, Naijá , ff, Naajeeriya, kcg, Naijeriya officially the Federal Republic of Nigeria, is a country in West Africa. It is situated between the Sahel to the north and the Gulf o ...

Mozambique Mozambique (), officially the Republic of Mozambique ( pt, Moçambique or , ; ny, Mozambiki; sw, Msumbiji; ts, Muzambhiki), is a country located in southeastern Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi ...

, and on ''

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 ...

'', cotton and

sweet potato The sweet potato or sweetpotato (''Ipomoea batatas'') is a dicotyledonous plant that belongs to the Convolvulus, bindweed or morning glory family (biology), family, Convolvulaceae. Its large, starchy, sweet-tasting tuberous roots are used as a r ...

in the

DRC The Democratic Republic of the Congo (french: République démocratique du Congo (RDC), colloquially "La RDC" ), informally Congo-Kinshasa, DR Congo, the DRC, the DROC, or the Congo, and formerly and also colloquially Zaire, is a country in ...

References

Lygaeidae Hemiptera of Africa {{Heteroptera-stub