Landcare Research - Manaaki Whenua

Landcare-Research -Manaaki Whenua

FNZ 45 - Nemonychidae, Belidae, Brentidae (Insecta: Coleoptera: Curculionoidea) - Popular summary

Kuschel, G 2003. Nemonychidae, Belidae, Brentidae (Insecta: Coleoptera: Curculionoidea). Fauna of New Zealand 45, 100 pages.
( ISSN 0111-5383 (print), ; no. 45. ISBN 0-478-09348-9 (print) ). Published 28 Apr 2003

Popular summary

Orthoceri Weevils

This contribution deals with Orthoceri weevils of the families Nemonychidae, Belidae and Brentidae. Weevils are a major taxon of beetles characterised by a head extended into a proboscis or rostrum. They are plant-feeders as adult and larva. Depending on how important certain plants are to the economy of a country, weevils are perceived as beneficial, of no importance, or pests. They are usually of no importance in their native country, but can become pests in other countries. However, if noxious weeds have host-specific weevils in their original country, the weevils can be imported under strict quarantine conditions and may be released after ensuring that they are free of parasitoids and do not affect any native plants. New Zealand has already introduced and released weevils for the control of gorse and thistles, and is considering other introductions.

Weevils have existed for at least 140 million years, since the era of gymnosperms (cycads and conifers) and dinosaurs. Weevil fossils were already abundant well before flowering plants (angiosperms) appeared on earth. Gymnosperm species have since declined to very low numbers, and angiosperms, known only since Cretaceous times, have proliferated to some 200 000 species worldwide. Early weevils had a long rostrum, with long, slender mandibles and long labial and maxillary palps. These mouthpart features strongly suggest that ancestral weevils were pollen-feeders. Gymnosperms have large male and female cones (strobili), and the male cones produce copious amounts of highly nutritious pollen. Therefore it is assumed that Jurassic weevils would have been specialist pollen feeders, because all extant nemonychid species still have pollen as their sole or main diet.

Conventionally, weevils are divided into two convenient groups: Orthoceri, defined by having all antennal segments following a straight line, and Gonatoceri, characterised by 'broken'or elbowed antennae, the result of a deviation in an angle of the segments following the basal one (scape). All Jurassic and Lower Cretaceous weevils were Orthoceri with straight antennae associated with gymnosperms. The vast majority of extant Nemonychidae, and some Belidae, retain an association with gymnosperms and still live exclusisvely on Araucariaceae, Podocarpaceae, and Pinaceae.

This contribution is devoted to the 3 Orthoceri families Nemonychidae, Belidae, and Brentidae (the other Orthoceri family Anthribidae, with 58 species, has been revised by Holloway (1982), Fauna of New Zealand 3). Although these 3 families are poorly represented in New Zealand, with only 16 native and 1 introduced species, they are of considerable biological, phylogenetic, and biogeographical interest. All 4 species of Nemonychidae, and 5 out of 6 species of Belidae, are associated with Podocarpaceae (totara, rimu, matai, kahikatea and relatives) and Phyllocladacaeae (tanekaha, toatoa). Whilst the Nemonychidae of New Zealand are closer to the Chilean species found on Podocarpaceae than to the Australian ones found on Araucariaceae, 5 species of Belidae show a definite close affinity to Australia. The sixth belid species belongs to a New Caledonian genus associated with Araliaceae.

The family Brentidae has 2 dissimilar subfamilies in New Zealand: Brentinae and Apioninae. Brentinae are represented by an endemic genus and species known as the giraffe weevil (pepeke nguturoa): The size difference and the sexual dimorphism of this species is spectacular. The giraffe weevil is unique in being the sole weevil species in the world with a visible scutellum. It is also unique in that some of its males can be over 8 cm long, thus easily surpassing the length of any other brentine. The subfamily Apioninae is represented by 5 native and 1 foreign species, the latter purposely introduced for a partial control of gorse (Ulex europaeus). Three genera, with a single species each, are endemic. They are not close to each other or to anything else outside New Zealand. One genus (Zelapterus) has a very small, smooth, and shiny species that is flightless and still has no known host. Another genus (Cecydophyus) is represented by a large, dull, and hairy species, whose host is silver beech (Nothofagus menziesii). The third genus (Strobilobius) has a species with hairless, deeply sculptured elytra, and is of considerable interest because of its association with the coniferous pahautea (Libocedrus bidwillii) of the cypress family. The fourth apionine genus (Neocyba) is also endemic, with 2 species associated with rata and pohutukawa (Metrosideros spp.). It is closely related to a genus from New Caledonia.