Curculio

Linnaeus, 1758

acorn weevils, nut weevils

Species Guides

Curculio is a of weevils in the Curculionidae, commonly known as acorn weevils or nut weevils. Females use their elongated rostrum to bore holes in developing nuts of oak, hickory, and other trees to deposit . Larvae develop inside the seeds, feeding on the nutritious kernel, then emerge in autumn to pupate in soil. The genus has been extensively studied due to its economic impact on nut production and its remarkable morphological adaptations for seed .

Curculio rubidus by (c) Barry Walter, some rights reserved (CC BY), uploaded by Barry Walter. Used under a CC-BY license.

Curculio proboscideus by (c) Christopher Zacharias, some rights reserved (CC BY), uploaded by Christopher Zacharias. Used under a CC-BY license.

Curculio proboscideus by (c) Jennifer Harris, some rights reserved (CC BY), uploaded by Jennifer Harris. Used under a CC-BY license.

Pronunciation

How to pronounce Curculio: //kʊrˈkuː.li.oʊ//

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

Distinguished from other weevil by the combination of extremely elongated rostrum, association with nut-bearing trees, and small body size. Separated from similar acorn-feeding weevils by rostrum length and the absence of oviposition-deterring . -level identification requires examination of genitalia and subtle morphometric differences.

Images

Habitat

Woodlands and forests containing oak (Quercus) and hickory (Carya) trees; also found in landscapes and orchards where trees occur. occur in tree during the breeding season; larvae develop within nuts; occurs in soil.

Distribution

Widespread in North America and Europe; recorded from England, Wales, Scandinavia, eastern Canada, and the United States. Distribution closely follows that of oak .

Seasonality

emerge from soil in spring coinciding with oak leaf and acorn development. Breeding occurs during summer when acorns are developing. Larvae exit nuts in autumn when acorns fall. occurs in soil, with adults emerging after one to two years.

Diet

Larvae feed exclusively on the kernel (cotyledon) of developing acorns and other nuts. feed on oak foliage and other plant material, though specific adult diet is poorly documented.

Host Associations

Quercus - larval developmentacorns
Carya - larval developmenthickory nuts

Life Cycle

Complete . are laid in galleries excavated by females in developing nuts. Larvae are legless, creamy-white that feed internally on the nut kernel. Mature larvae chew exit holes through the shell and drop to the ground, burrowing into soil to pupate. The soil-dwelling phase lasts one to two years before .

Behavior

Females use jaws at the rostrum tip to cut shallow galleries in acorn husks for deposition, despite possessing a long rostrum capable of deeper penetration. Females produce more galleries than needed for egg-laying. Larvae exhibit at high densities, which functions as a competitive reduction strategy. climb to tree to feed and oviposit.

Ecological Role

Primary seed of oak and hickory; significant mortality agent for acorn crops. fluctuations track mast years (periods of heavy acorn production). Serves as food source for vertebrate predators including birds, squirrels, and other acorn-feeding mammals that consume infested nuts.

Human Relevance

Economic pest of nut production, particularly in oak silviculture and ornamental plantings. Infested acorns are unmarketable and show reduced germination rates. Subject of research. of C. glandium sequenced as part of Darwin Tree of Life project.

Similar Taxa

Conotrachelus nenupharAlso a weevil with elongated rostrum that infests fruits, but attacks stone and pome fruits (plums, apples, peaches) rather than nuts; causes external scarring and internal larval feeding distinct from Curculio's seed
Other Curculionidae genera (e.g., Sitona, Hypera)Share -level characteristics but lack the extreme rostrum elongation and specialized nut-boring oviposition ; feed on foliage, roots, or legumes rather than tree seeds

More Details

Reproductive biology

Females can lay up to eight per acorn. Unlike some weevil , Curculio females do not produce oviposition-deterring that would prevent multiple females from using the same acorn. This leads to potential larval competition and .

Mast year dynamics

respond dramatically to mast years—periods of exceptional acorn production by oak trees. During these years, weevil reproductive success increases substantially, with cascading effects on vertebrate populations that depend on acorns.

Acorn selection

Females preferentially select larger acorns over smaller ones, and breed later in the season compared to sympatric acorn weevil , suggesting temporal partitioning among competitors.