Weevils, curculios or snout beetles

Code QCAN0000

Only one group of weevils may routinely occur in aquatic samples: the subfamily Erirhininae. Most members of this subfamily have the spiracles drawn out into paired dorsal spines, which allows easy separation from the otherwise similar Brentidae. If such spines are not apparent, erirhininid larvae may still be distinguished from the aquatic brentid Nanophyes by the presence of 1-2 pairs of stemmata (brentids have none) and the 2-segmented labial palp (1-segmented in Nanophyes ). Note that the key only separates truly aquatic curculionids and brentids - it may not work for terrestrial individuals that have occurred incidentally.

Other characters of erirhininids include the lack of legs and generally curled, grublike abdomen (though in some instances the abdomen may appear more slender and elongate). Mature larvae around 3.5mm long. Sclerotisation highly reduced to absent. Antenna of one reduced membranous segment, bearing a sensory appendage. Abdomen lacking urogomphi, hooks, gills, pygopods or other appendages.

Curculionidae (Polyphaga: Curculionoidea) is the most speciose family of beetles, indeed of any taxon, with around 6000 species known from Australia. Most species are terrestrial. All feed on living plants. The subfamily Erirhininae are well-suited to a fully submerged existence - adults possess a ventral plastron, whilst most larvae possess the spinose spiracles discussed above, used to tap internal air spaces of aquatic plants for oxygen. Some larvae may live in air-filled burrows within aquatic plants. This subfamily includes the introduced Cyrtobagous salviniae , control agent for salvinia weed in waterways.

References:

Anderson, D.M. (1991) Curculionidae (Broad Sense) (Curculionoidea) pp. 594-612. In: Stehr, F.W. (ed.) Immature Insects. Volume 2. Kendall/Hunt Publishing Company, Dubuque, Iowa.

Lawrence, J.F. and Britton, E.B. (1991) Coleoptera. pp. 543-683. In: CSIRO, Insects of Australia. Volume 2. Melbourne University Press, Carlton, Victoria.

Williams, W.D. (1980) Australian Freshwater Life: The Invertebrates of Australian Inland Waters. The Macmillan Company of Australia, Melbourne.