Animals

Weevils

by Marcia Malory

Weevils are beetles that belong to the superfamily Curculionoidea.

All weevils are vegetarians.

They are found on many different types of plants. Some are highly specialized to live on and feed off a particular host plant.

Weevils will eat almost all parts of plants.

Some weevils are nut-borers, while others may be stem borers, bud eaters or leaf rollers.

Weevils may burrow into fruits and roots or eat parts of leaves.

They are infamous for destroying crops.

Weevils are often brightly colored.

Their heads are usually drawn out into a long, snout that resembles a beak. This snout, which is known as a rostrum, contains a pair of antennae. Tiny jaws are located at the tip of the rostrum.

Many weevils can protect their antennae by folding it into grooves at the side of the rostrum.

Nut-boring weevils belong to the genus Curculio.

Hazelnut Weevil, photo by Entomart, BelgiumThe hazelnut weevil (Curculio nucum) has a black upperside with yellow-brown flecks. Its legs and antennae are rust colored.

It can be found in England and Scotland, living in woodlands and hedgerows.

Adults eat hawthorn flowers.

The females lay their eggs in young hazelnuts.

In early summer, the female hazelnut weevil uses her snout to bore a hole into the soft shell of a young green hazelnut and then deposits an egg into the hole.

When the larva hatches, it feeds on the nut kernel.

In autumn, the nut falls to the ground. The larva eats its way out of the shell and buries itself into the soil, where it becomes a pupa.

It emerges as an adult in the spring.

Apple blossom weevils hibernate in sheltered places, for example, in leaf debris or behind loose bark.

Acorn Weevil, photo by Elke FreeseCurculio villosus, Curculio venosus and Curculio glandium are nut-boring beetles known as acorn weevils because they lay their eggs in acorns.

The red oak roller (Attelabus nitens) has a red body, with black legs and head.

Females are around ¼ inch long; males are slightly smaller.

Red oak rollers usually live on the leaves of young oaks.

When the female lays her egg, she places a single egg on an oak leaf, then rolls up the leaf to protect the larva.

The birch leaf roller, which is often found on birch trees in Great Britain, is smaller than the red oak roller. It is between three and five millimeters long.

The female birch leaf roller also rolls up leaves to provide homes for its larvae.

Byctiscus betulae is another leaf roller that lives on birch trees. It is most common in the south of England. Byctiscus betulae is either green, dark metallic blue or shiny red-brown. The male has a small spike that projects forward on each side of its thorax.

Figwort weevils belong to the genus Cionus.

They are square-shaped, with long rostrums and short, stout legs and can usually be found in groups, on the leaves of heir food plants.

The larvae are coated with slime, which probably prevent birds from eating them.

The slime eventually forms a tough cocoon, which is firmly attached to the food plant.

Inside the cocoon, the pupa is transformed into an adult beetle.

After biting its way out of the cocoon, it hibernates at the base of a tuft of grass or in leaf litter.

Cionus scrophulariae, which can be found throughout Great Britain, feeds on the common figwort, the water figwort and the common mullein.

It is about 4 to 4.5 millimeters long.

Its thorax is covered with whitish or pale yellow scales and its wing cases are grey with black spots.

Its antennae are reddish with darker ends, and its legs are black with brown tips.

The apple blossom weevil (Anthonomus pomorum), which is common in England and Wales, can be found where apples grow.

It is a dark, ashy red, with two broad grayish stripes that form a flattened V shape.

Apple blossom weevils live almost exclusively on the leaves of young apple trees, although they will sometimes eat pear leaves as well.

When the female lays her eggs, she uses her rostrum to bore a hole into an unopened blossom bud, then turns around and places an egg into the hole.

Each female lays about 50 eggs.

When the grub hatches, it eats its way into the bud, destroying it.

The grub then eats the base of the flower.

After about two weeks, the grub becomes a pupa. Seven to ten days later, it becomes an adult.