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Acorn Weevil - Curculio sp.
Order Coleoptera Linnaeus, 1758 -- beetles, besouro, coléoptères /
Suborder Polyphaga Emery, 1886 / Infraorder Cucujiformia Lameere, 1938
Superfamily Curculionoidea Latreille, 1802 / Family Curculionidae
Latreille, 1802 -- charançons, snout beetles, weevils / Genus Curculio
Linnaeus, 1758
Live adult weevils photographed at Winfield Mounds Forest Preserve,
DuPage County, Illinois, USA.
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There are over 35,000 species of weevil worldwide, with more than 2,500 species in
North America. All are strictly herbivorous.
Weevil is the common name for
beetles of
the snout beetle family Curculionidae. They are usually small,
hard-bodied insects. The mouthparts of snout beetles are modified into
down-curved snouts, or beaks, adapted for boring into plants; the jaws
are at the end of the snout. The bent antennae usually project from the
middle of the snout. In the case of the acorn weevils, the snout can
actually be longer than the body.
The acorn weevil, Curculio, is
one of the weevils that infest hardwood nuts. These weevils attack
both red and white oaks and are found wherever the hosts grow. These live adult
weevils were found in a large grove of Butternut, Shagbark Hickories and
Oak trees at the original site of the
Native American burial mounds at Winfield, IL USA. |
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Acorn Weevil |
Acorn weevils have snouts with small, saw-like teeth at the very end.
There are two types, or genera: the long-snouted acorn weevils (genus
Curculio) and the short-snouted ones (genus Conotrachelus). The
longsnouted acorn weevil's snout may be equal to or greater than the
length of its body. These specimens are, of course, the long-snouted
variety.
Adults of both genera feed on acorns, but only the long
snouted weevils can drill into the shells to feed and lay eggs inside
the nutmeat. The tip of the snouth is actually a miniature saw, and the
weevil places the tip against the shell, circling endlessly around the
pivot point until the shell is pierced. Females place eggs inside the
nut using a long ovipositorthat descends from the abdomen.
Grub-like acorn weevil larvae hatch from eggs a few days
after they are laid. There may be one to several acorn weevil larvae in
each acorn. Larvae typically go through five growth stages, or instars.
Each instar ends with the molt or shedding of the old skin, providing
the larva with more room to grow. After a few weeks, larvae chew their
way out of the acorn, burrow into the soil to pupate, and eventually
emerge as adults the next year. Short-snouted larvae usually exit from a
single hole that already exists in the acorn, but long-snouted larvae
may chew their own exit hole through the acorn shell. Like larvae of the
short-snouted acorn weevil, acorn moth larvae can feed only on damaged
or sprouting acorns. The grayish female acorn moths lay eggs in damaged
acorns, sometimes in the emergence holes of acorn weevil larvae. It's
easy to distinguish the acorn moth larva, a caterpillar, from acorn
weevil larvae. The acorn moth larva has three pairs of legs near the
head and is generally longer than the legless, fat larvae of acorn
weevils. Larvae of the acorn moth feed on acorns and probably on the
fungi that often grow in damaged acorns. They usually pupate inside the
acorns.
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