Robert S. Anderson. 1998. Weevils (Curculionoidea) in Smith, I.M., and G.G.E. Scudder, eds. Assessment of species diversity in the Montane Cordillera Ecozone. Burlington: Ecological Monitoring and Assessment Network, 1998.

WEEVILS (CURCULIONOIDEA)

(excluding Scolytidae, Platopodidae)

Robert S. Anderson

GENERAL BIOLOGY

Most weevils feed as adults and immatures on the living tissues of angiosperm plants although there are a number of subfamilies (e.g., Cryptorhynchinae, Zygopinae) in which species feed on dead or dying plant tissues, most often wood. There are also a few examples of exotic species associated with ants, some dung feeders, and at least one species is recorded as a predator (Anderson 1997). Weevils are generally terrestrial although a few species are found in freshwater wetland habitats. Terrestrial habitats vary from alpine meadows, various types of forests, to dry deserts. Weevils are one of the most successful groups of insects in arid habitats (Moran 1980). Aquatic weevils include Erirhininae (some Erirhinini [excluding Dorytomus], Tanysphyrini, Bagoini) and Ceutorhynchinae (Cnemogonini, Phytobiini). Immatures of these species are generally endophytic in emergent aquatic macrophytes although some ceutorhynchine larvae feed externally.

With a few exceptions, feeding habits within Curculionidae can be loosely classified into two groups (Anderson 1997). In one group, composed of the Brachyderinae and Otiorhynchinae, adults and larvae tend to be polyphagous. The larvae of most species feed externally upon roots in the soil whereas the adults tend to feed generally on foliage. In the second group, composed of most remaining taxa, both adults and larvae are oligophagous, and have a more restricted taxonomic range of host plants. Larvae of most species are internal feeders on other parts of the plant such as the stem, leaves, or reproductive structures (flower buds, fruits and seeds), or in a few instances, are external feeders on plant foliage. Species in most plant families, especially those in the angiosperms, serve as host plants of weevils. Collectively, weevil immatures feed upon virtually all plant parts.

With about 48,000 species in 4300 genera presently described (Kuschel 1995), the family Curculionidae is generally recognized as the most species diverse family of living organisms. Anderson (1995) hypothesized that the rostrum of the adut female weevil serves the same function as an ovipositior and has in turn allowed weevil immature stages access to most if not all plant anatomical parts (even those protected by hard external coverings) as food. This ability, coupled with an evolutionary origin which appears to have been concurrent with the onset of angiosperm radiation, has led to the tremendous species diversity of weevils present today. Weevils tend to be most diverse at tropical latitudes with diversity generally dropping towards the north (Anderson 1997).

An excellent review of weevil biology is by Morris (1991).