Definitions

granary weevil

Weevil

[wee-vuhl]
A weevil is any beetle from the Curculionoidea superfamily. They are usually small, less than 6 mm (¼ inch), and herbivorous. Due to the shape of their heads, weevils are commonly known as snout beetles. There are over 60,000 species in several families, mostly in the family Curculionidae (the true weevils). Some other beetles, although not closely related, bear the name "weevil", such as the biscuit weevil (Stegobium paniceum), which belongs to the family Anobiidae.

Many weevils are damaging to crops. The grain or wheat weevil (Sitophilus granarius) damages stored grain. The boll weevil (Anthonomus grandis) attacks cotton crops. It lays its eggs inside unripe cotton bolls, and the young weevils eat their way out.

Weevils are often found in dry foods including nuts and seeds, cereal and grain products. In the domestic setting, they are most likely to be observed when opening a bag of flour although they will happily infest most types of grain including oats, barley and breakfast cereals. Their presence is often indicated by the granules of the infested item sticking together in strings, as if caught in a cobweb. If ingested, E. coli infection and other various diseases can be contracted from weevils, depending on their diet.

Taxonomy

Because there are so many species and such diversity, the higher classification of weevils is in a state of flux. Weevils are generally divided into two major divisions, the Orthoceri or primitive weevils, and the Gonatoceri or true weevils (Curculionidae). Zimmerman proposed a third division, the Heteromorphi, for several intermediate forms . Primitive weevils are distinguished by having straight antennae, while true weevils have elbowed (geniculate) antennae. The elbow occurs at the end of the scape (first antennal segment) in true weevils, and the scape is usually much longer than the other antennal segments. Some exceptions occur. Nanophyini are primitive weevils (with very long trochanters) but have long scapes and geniculate antennae. From the true weevils, Gonipterinae and Ramphus have short scapes and little or no elbow.

The most recent classification system to family level was provided by Kuschel , with updates from Marvaldi et al. , and was achieved using phylogenetic analyses. The accepted families are the primitive weevils, Anthribidae, Attelabidae, Belidae, Brentidae, Caridae and Nemonychidae, and the true weevils Curculionidae. Most other weevil families were demoted to subfamilies or tribes. Weevil species radiation was shown to follow steps in plant evolution upon which the weevils feed.

Some of the features used to distinguish weevil families are:

Labrum visible as separate segment to clypeus Anthribidae, Nemonychidae
Antennae elbowed most Curculionidae, Nanophyini of Apioninae
Trochanters (segment between coxae and femora) as long or longer than coxae Apioninae including Nanophyini
Fore tibia with comb of setae in apical groove opposite tarsal articulation Belidae
Elytra striate (with longitudinal ridges or grooves) Brentidae, Curculionidae, Rhinorhynchinae
Rostrum short and broad Anthribidae, some Curculionidae (some Brachycerinae including Ithycerus (New York weevil), Scolytinae and Platypodinae).
Maxillary palps long and projecting (visible from above at tip of rostrum) Anthribidae, Nemonychidae
Abdominal tergites 6 and 7 without spiracles Caridae
Gular suture (on ventral part of head) single not double Attelabidae, Brentidae, Curculionidae.

Phylogeny

A phylogeny of the Curculionoidea based on 18S ribosomal DNA and morphological data is suggested below:

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Trivia

  • In Steven Spielberg directed 1987 film "Empire of the Sun", main character Jamie Graham aka Jim (played by Christian Bale) eats weevils for their protein content in order to survive malnutrition while being held prisoner by the Japanese during the Second World War.
  • In the episode Evil Weevil of Courage the Cowardly Dog a weevil works as the butler for the Bagges, but actually wanted to suck Muriel and Eustace's blood.
  • In the movie Master and Commander: The Far Side of the World captain Jack Aubrey (played by Russell Crowe) makes a joke about "choosing the lesser of two weevils".
  • In the book Crossroads of Twilight, book ten in The Wheel of Time series by Robert Jordan, concerns about weevils destroying stores of grain are frequent.
  • In the Hornblower Series by C. S. Forester, weevils are a common pest eating up the ship's biscuit supplies.
  • Zyzzyva, a genus of tropical American weevils, is the last word in many English language dictionaries including The Official Scrabble Players Dictionary.
  • In the episode The Night of the Headless Woman of The Wild Wild West the episode's bad guy, Abdul Hassan plans to infest all western countries with giant boll weevils so that he can get rich supplying the West with cotton.
  • In Season Four Episode Eleven of The Office, Dwight refers to 'Weevil season' after Ryan asks Dwight a question about his Beet Farm.
  • In the TV show "Back at the Barnyard" the farmer says that Weevils are the only bug he's ever feared.
  • If every species of animal and plant were placed next to each other in a line, every 10th animal would be a weevil.
  • The Nintendo 64 game Jet Force Gemini contains anthropomorphized weevils as enemies.
  • The popular series of Flash Cartoons, "Blockhead," features a recurring character described as a 'ravenous hobo,' named the Weevil.

" In Carry On Columbus the crew of columbuses ship whilst sitting down to dinner find little black insects which is described as sounding like weevils.

References

  • Bright, Donald, E., Bouchard, P. (2008) Coleoptera, Curculionidae, Entiminae. Weevils of Canada and Alaska — Volume 2. Insects and Arachnids of Canada Series, Part 25 Ottawa: NRC Research Press. ISBN 978-0-660-19400-4.

External links

On the UF / IFAS Featured Creatures Web site

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