Weevil

Weevils are a type of beetle belonging to the superfamily Curculionoidea. They are usually small, less than 6 mm (0.24 in), and herbivorous. About 97,000 species of weevils are known. They belong to several families, with most of them 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 Ptinidae. Many weevils are considered pests because of their ability to damage and kill crops. The grain or wheat weevil (Sitophilus granarius) damages stored grain. The boll weevil (Anthonomus grandis) attacks cotton crops; it lays its eggs inside cotton balls and the larvae eat their way out. Other weevils are used for biological control of invasive plants. Some weevils have the ability to fly, such as the rice weevil. One species of weevil, Austroplatypus incompertus, exhibits eusociality, one of the few insects outside the Hymenoptera and the Isoptera to do so. Because so many species exist in such diversity, the higher classification of weevils is in a state of flux. They are generally divided into two major divisions, the Orthoceri or primitive weevils, and the Gonatoceri or true weevils (Curculionidae). E. C. 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; they can vary in color from black to light brown.