Sitophilus

Sitophilus is a genus of weevils in the tribe Litosomini. Some species are familiar as pests of stored food products. Notable species include the rice weevil (S. oryzae), wheat weevil (S. granarius), and maize weevil (S. zeamais).

Sitophilus
Sitophilus granarius
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Coleoptera
Family: Curculionidae
Subfamily: Dryophthorinae
Tribe: Litosomini
Genus: Sitophilus
Schoenherr, 1838[1]
Species

14, see text

Distribution

The rice and maize weevils have a nearly cosmopolitan distribution, occurring throughout the warmer parts of the world. In Europe they are replaced by the temperate Palaearctic wheat weevil.

Biology

The adult female weevil bores a hole in a grain, nut, or seed, and deposits an egg, usually one egg per individual grain. She seals the hole with a secretion. The larva develops while feeding on the interior of the grain, and then pupates. It usually leaves the grain completely hollow when it exits as an adult.[2] The wheat weevil can live on acorns, and may have used them as a host before agriculture made grain plentiful. The rice weevil can live on beans, nuts, grains, and some types of fruit, such as grapes.[3] Several other Sitophilus use the acorns of oaks such as bluejack oak (Quercus incana) and moru oak (Q. floribunda). Some use the seeds of trees in the Dipterocarpaceae and the legume family, Fabaceae. The tamarind weevil (S. linearis) is only known from the seeds of tamarind.[2]

Several Sitophilus species are hosts to an intracellular γ-Proteobacterium. Weevil and bacterium have a symbiotic relationship in which the bacterium produces nutrients such as amino acids and vitamins for the host, supplementing its cereal diet.[4]

Diversity

As of 1993, there are about 14 species of Sitophilus.[2]

Species include:[2]

  • Sitophilus conicollis
  • Sitophilus cribrosus
  • Sitophilus erosa
  • Sitophilus glandium
  • Sitophilus granarius – wheat weevil, granary weevil
  • Sitophilus linearis – tamarind weevil
  • Sitophilus oryzae – rice weevil
  • Sitophilus quadrinotatus
  • Sitophilus rugicollis
  • Sitophilus rugosus
  • Sitophilus sculpturatus
  • Sitophilus vateriae
  • Sitophilus zeamais – maize weevil

Fossil taxa include:

  • Sitophilus punctatissimus

References
  1. Schoenherr (1838). Gen. et Sp. Curc. 4(2): 967.
  2. Plarre, R. (2010). An attempt to reconstruct the natural and cultural history of the granary weevil, Sitophilus granarius (Coleoptera: Curculionidae). Eur J Entomol 107, 1-11.
  3. Ebeling, W. Chapter 7: Pests Of Stored Food Products. Urban Entomology. University of California, Riverside.
  4. Vallier, A., et al. (2009). RNAi in the cereal weevil Sitophilus spp: systemic gene knockdown in the bacteriome tissue. BMC Biotechnology 9(1), 44.
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