Snout Beetles - Curculionoidea
The Curculionoidea are a superfamily of beetles including a number of important
families, most of which are equipped with long beaks or snouts. The mouthparts
of these beetles are small and usually hidden from view. In most cases, the
mandibles, situated at the end of the snout, are the only mouthparts that can be
seen without dissecting the insect. Commonly called snout beetles, the
Curculionoidea include many serious pests of food crops, stored foods, and
trees. Their larvae are often legless.
Brentids are easily recognized by
their elongate body form; straight antenna; and long, often
remarkably sexually dimorphic rostrum
The long, slender beetles of the family Brentidae, sometimes called
the straight-snouted weevils, are usually found under bark or living in the
nests of ants and termites. Most brentids inhabit the tropics; only six species
may be found in North America. The most common North American species is
Platysystrophus minutus, which is usually found under the bark of dead beech,
poplar, and oak trees.
The brentids have long straight snouts that are usually chisel-shaped at the
tip. The eyes are small and located a considerable distance from the mouthparts.
In Zetophloeus pugionatus, a species found in Madagascar, the elytra are
extended at the tips, causing this handsome black and red beetle to appear to
have snouts at both ends.
Peculiar structural features are found in several other species of the
Brentidae. Calodromus mellyi, for example, displays unusually structured hind
legs in which the first tarsal segment is swollen, tipped with tufts of hair,
and frequently almost as long as the beetle itself. C. mellyi is found in the
The South American species Estenorrhinus designatus differs from other brentids
in that its snout is short and thick and capped with large sharp mandibles.
Attelabidae. The so-called leaf-rolling weevils
of the family Attelabidae are small, compact beetles, often beautifully colored
in red and black. The females are notable in that each lays a single egg near
the tip of a leaf and then proceeds to roll the leaf into a neat, cigar-shaped
When the egg is securely encased in this leaf roll, the female chews through the
leaf near the stem and the roll drops to the ground. When the larva emerges from
the egg, it feeds on the leaf ^oll and, in some cases, even pupates in it.
Apionidae. The tiny, pearshaped beetles of this family are usually seen in
cultivated fields and on summer flowers. They are blue, dark green, or even
orange in color. Their larvae often bore into plant stems, where they cause the
formation of galls.
The Apionidae are divided into two sub-families. In members of the subfamily
Nanophyinae the antennae are elbow shaped;
members of the subfamily Apioninae have straight antennae.
Curculionidae. This is the largest family of the superfamily Curculionoidea. Its
members vary considerably in size, shape, and color, but in most species the
snout is long. The antennae are usually located on the middle of the snout.
One of the most serious pests in this family is
Calandra granaria, the grain weevil. This tiny black beetle is found in
incredible numbers in such stored foodstuffs as rice, buckwheat, dried beans,
peas, chestnuts, and wheat. C. granaria not only feeds on these materials-it
often carries molds and fungi that cause more damage than the beetle itself.
Interestingly, the grain weevil avoids foodstuffs with a high oil content such
as cocoa beans and green coffee. The grain weevil is a remarkably hardy insect,
able to survive low temperatures and go without water for as long as 10 days. It
has no rear wings and therefore must patiently wait to be transported from place
Curculionids of the genus Curculio, commonly called nut beetles or acorn
beetles, can be recognized by long, slender snouts that may be longer than the
beetle itself. These beetles bore into nuts or acorns to lay their eggs. The
larvae develop inside the acorns or nuts. Many species are regarded as pests.
Curculio nucum prefers walnuts; C. elephas favors chestnuts and acorns; and C.
caryae attacks hickory nuts and pecans.
Commonly found in North America, curculionids of the genus Lixus are elongate
and usually somewhat tapered at both ends. They are usually found near water.
One wellknown species is L. concavus, a black beetle covered with gray hair.
Known as the rhubarb curculio, it is usually seen on the stems of sunflowers,
dock, and rhubarb.
One of the most serious pests in this family is Anthonomus grandis, the boll
weevil. The adults spend the winter months in woods or other protected areas. In
the spring they move to cottonfields, where they feed on the blooms, seed pods,
and bolls of cotton plants. The female lays her eggs inside the bolls. The eggs
hatch in 3 to 5 days; the white larvae feed on the bolls for 7 to 14 days before
The boll weevil is thought to have traveled from Mexico to the United States in
about 1800. Since then it has spread to most areas where cotton is cultivated.
Several close relatives of the boll weevil are also serious pests, among them
the strawberry weevil, Anthonomus signatus; the cranberry weevil, A. musculus;
and the apple curculio, Tachypterellus quadrigibbus.
Scolytidae. Of all the insects, the small, dark, cylindrical beetles of the
family Scolytidae are the most serious pests of trees. The family is divided
into two groups: the bark, or engraver, beetles, and the ambrosia, or timber,
beetles. The adults and larvae of both groups bore long tunnels or galleries in
wood, an activity that eventually kills the trees in which they live.
Among the serious pests in this family are the fruit-tree bark beetle, SjQplytus
rugulosus. which attacks cherry, peach, apple, and other types of trees. The
European elm bark beetle, Scolytus multistriatus, is the carrier of the
destructive Dutch elm disease. The clover root borer, Hylastinus obscurus,
damages especially red clover. Two major pests on pine trees are Dendroctonus
piceaperda and D. ponderosa.
The bark beetles live between the bark and wood of trees. The tunnels they bore
etch the surface of the heartwood-thus the name engraver beetles-but do not
actually enter the interior of the tree. The adults first bore through the bark
of a tree and then dig a gallery or group of galleries in which the female's
eggs are laid. When the eggs hatch, the larvae begin to bore their own tunnels,
moving away from the gallery where they were born. They continue to dig
throughout the larval stage, and then pupate at the end of the tunnel. The
emerging adults then bore through the bark leaving the tree pocked with hundreds
of tiny holes-and the cycle begins again.
The timber beetles, on the other hand, actually bore into the hardwood. They do
not feed on the wood, preferring to get their nourishment from fungi they
cultivate in their complex of galleries and tunnels. The females lay their eggs
in small cells joining the main galleries, and the larvae are fed by the adults
until they pupate. The adults supply the larvae with fungi and tirelessly carry
away the excrement of their young in order to keep the galleries clean. When the
adults fly to a new tree they carry with them bits of fungi, thus providing a
continuing source of food.
All scolytids work in pairs or in family units consisting of a male and a harem
of females. The various species of this family are characterized by the kind of
trees in which they live and by the patterns made by the tunnels they bore.