T.E.R:R.A.I.N - Taranaki Educational Resource: Research, Analysis and Information Network


Weevil (White-fringed) Naupactus leucoloma

Kingdom: Animalia
Phylum: Arthropoda)
Subphylum: Hexapoda
Clade: Euarthropoda
Class: Insecta
Order: Coleoptera
Family: Curculionidae
Genus: Naupactus
Species: N. leucoloma
Binomial name: N. leucoloma
Scientific name: Naupactus leucoloma
Common names: White-fringed weevil



Naupactus leucoloma is a species of broad-nosed weevil that was originally from South America (Argentina, Peru, Chile, Uruguay). It is now widely distributed throughout New Zealand where it is found throughout the North Island and much of the South Island. They thrive in warm moist conditions. The adults chew the leaf margins of a wide range of broadleaf plants. Their larvae feed on the roots of a variety of plants, preferring legumes. The larval stage is the most damaging life stage as it feeds on the plant’s roots and their underground stems. They also chew holes or shallow channels in potato tubers. 
Some of its host plants are the potato (Solanum tuberosum), lucerne (Medicago sativa), kumera (Ipomoea batatas), soybean (Glycine max), onion (Allium cepa), white clover (Trifolium repens), peanut (Arachis hypogaea), grapevines (Vitis vinifera). Grape vines can suffer severe damage to the vines underground parts. The adults can completely ring bark young vines, which usually don't recover, or if they do, they are severely compromised and open to infection from fungi.
The flightless, adult weevils are a slate-grey with a distinctive lateral white band along the margins of the elytra, and two pale longitudinal lines on each side of the thorax and head (one above and below the eye). They are 12-15 mm in length. 
Naupactus leucoloma has a long-lifecycle (224 to 672 days in New Zealand), most of which is spent underground as grubs. Female of this species are parthenogenic so females don’t need to mate before producing eggs. White eggs are laid on the soil during January or February, and when the larvae hatch they burrow into the soil where they spend the winter feeding on plant roots and grow to around 13 mm in length. The eggs need moisture to hatch. This is likely why they are more of a problem in irrigated crops.
Mature larvae are cream coloured and quite solid in appearance, with no legs. The larvae’s yellow-brown head is generally not seen as it is retracted into the body. Their large black jaws are clearly seen protruding.




A photo showing the distinctive lateral white band along the margins of the elytra
 

The larva.


A drawing of the life cycle of and damage resulting from White-fringed weevils.


Thanks to Wikipedia for text and information: https://creativecommons.org/licenses/by-sa/3.0/