Weevils and Snout Beetles, Superfamily Curculionoidea

Weevils are odd-looking creatures, with their comically long snouts and seemingly misplaced antennae. But did you know they're actually beetles, just like ladybugs and fireflies? Both weevils and snout beetles belong to the large beetle superfamily Curculionoidea, and share certain common habits and traits.

Description:

It's difficult to offer a general description for such a varied group of insects, but you can easily identify most weevils and snout beetles by an extended "snout" (actually called a rostrum or beak). A few groups within this superfamily, most notably the bark beetles, lack this feature, however. All but the primitive weevils have elbowed antennae, extending from the snout. Weevils and snout beetles have 5-segmented tarsi, but they appear 4-segmented because the fourth segment is quite small and obscured from view without careful inspection.

Weevils and snout beetles, like all beetles, have chewing mouthparts. While it may appear by its shape that a weevil's long snout is for piercing and sucking (like true bugs), it is not. The mouthparts are quite small and located at the end of the rostrum, but are designed for chewing.

Most weevil and snout beetle larvae are white or cream in color, legless, cylindrical, and shaped like a C. They tend to burrow, whether in a host plant or other food source.

Families in the Superfamily Curculionoidea:

Classification within the superfamily Curculionoidea varies, with some entomologists dividing the group into just 7 families, and others using as many as 18 families. I've followed the classification accepted by Triplehorn and Johnson (Borror and Delong's Introduction to the Study of Insects, 7^th edition) here.

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• Family Nemonychidae – pine flower snout beetles
• Family Anthribidae – fungus weevils
• Family Belidae – primitive or cycad weevils
• Family Attelabidae – leaf-rolling weevils, thief weevils, and tooth-nosed snouth beetles
• Family Brentidae – straight-snouted weevils, pear-shaped weevils
• Family Ithyceridae – Ithycerus noveboracensis
• Family Curculionidae – snout beetles, bark beetles, ambrosia beetles, and true weevils

Classification:

Kingdom – Animalia
Phylum – Arthropoda
Class – Insecta
Order – Coleoptera
Superfamily - Curculionoidea

Diet:

Nearly all adult weevils and snout beetles feed on plants, though they vary greatly in their preferences for eating stems, leaves, seeds, roots, flowers, or fruits. The primitive families of weevils (Belidae and Nemonychidae, primarily) are associated with gymnosperms, such as conifers.

The larvae of weevils and snout beetles vary greatly in their feeding habits. Though many are plant feeders, they generally prefer dying or diseased plant hosts. Some weevil larvae are highly specialized feeders, with peculiar dietary habits. One genus (Tentegia, found in Australia) lives and feeds in marsupial dung. Some weevil larvae prey on other insects, like scale insects or the eggs of grasshoppers.

Many weevils are serious pests of crops, ornamental plants, or forests, and have significant economic impact. On the other hand, because they feed on plants, some weevils can be used as biological control for invasive or noxious weeds.

Life Cycle:

Weevils and snout beetles undergo complete metamorphosis, like other beetles, with four life cycle stages: egg, larva, pupa, and adult.

Special Behaviors and Defenses:

Because this is such a large and diverse group of insects with a broad range of distribution, we find quite a few unique and interesting adaptations among its subgroups. The leaf-rolling weevils, for example, have an unusual way of ovipositing. The female leaf-rolling weevil carefully cuts slits into a leaf, lays an egg at the leaf tip, and then rolls the leaf up into a ball. The leaf drops to the ground, and the larva hatches and feeds on the plant tissue, safe inside. Acorn and nut weevils (genus Curculio) bore holes into acorns, and place their eggs inside. Their larvae feed and develop inside the acorn.

Range and Distribution:

Weevils and snout beetles number about 62,000 species worldwide, making the superfamily Curculionoidea one of the largest insect groups. Rolf G. Oberprieler, an expert in weevil systematics, estimates the true number of existing species may be closer to 220,000. There are currently about 3,500 species known to inhabit North America. Weevils are most abundant and diverse in the tropics, but have been found as far north as the Canadian Arctic and as far south as the tip of South America. They're also known to inhabit remote ocean islands.

_Sources:

• _{Borror and Delong's Introduction to the Study of Insects, 7^th edition, by Charles A. Triplehorn and Norman F. Johnson.}
• _{Encyclopedia of Entomology, 2^nd edition, edited by John L. Capinera.}
• _{Beetles of Eastern North America, by Arthur V. Evans.}
• _{Morphology and Systematics: Phytophaga, edited by Richard A. B. Leachen and Rolf G. Beutel.}
• _{"A World Catalogue of Families and Genera of Curculionoidea (Insects: Coleoptera)," by M. A. Alonso-Zarasaga and C. H. C. Lyal, Entomopraxis, 1999 (PDF). Accessed online November 23, 2015.}