acorn weevil

Curculio glandium is a type of seed beetle with a long rostrum and ovipositor, adapted for feeding on seeds. The length of the rostrum can help differentiate between male and female beetles. The larvae of Curculio glandium are short, cylindrical, and move using ridges on their bodies. Adults can grow to be 4 to 8 mm long. These beetles lay eggs in acorns, and the larvae feed on the fruit without damaging the embryo. Curculio glandium can harm acorn trees by infecting the seeds and preventing them from germinating.

Description

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Curculio glandium is a member of the genus Curculio, which comprises seed beetles. All members of Curculio have characteristically long rostrums and ovipositors, an adaptation that specifically developed by their reliance on seeds for food and reproduction. Male/female differentiation can be determined using the rostrum as the female’s is longer. The larvae are short, and cylindrical in shape, and move by means of ridges on the underside of the body. Adults can reach a length of 4 to 8 mm (0.16 to 0.31 in).

Life cycle

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Curculio glandium eggs are deposited in acorns by the adult weevil chewing channels into the fruit. The eggs are then released using an ovipositor, a long, narrow organ featured in female weevils. These do not reach the acorn’s embryo and are healed by the plant, sealing the holes and protecting the eggs from parasites. Upon hatching, either one or two larvae consume the fruit. While they may eat the entirety of the acorn, the larvae typically do not consume the embryo itself. Curculio glandium live throughout winter in the larval stage. The larvae are freeze avoidant, preventing their internal body fluids from freezing during the winter.

Ecology

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Curculio glandium can pose a large risk to acorn-bearing tree populations. They are highly effective at infecting acorns which can cause a widespread number of seeds to be incapable of germination, with a potential of rendering 70–90% of seeds incapable of germination.

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