Weevils are a diverse group of beetles, recognized by their distinctive elongated snouts. These insects undergo a complete metamorphosis, transforming through four distinct life stages: egg, larva, pupa, and adult.
The Weevil Life Cycle
This complete metamorphosis is similar to what butterflies experience, but it is specifically adapted to the weevil’s environment and food sources. The entire life cycle can vary in duration depending on the species and environmental conditions, sometimes completing in as little as 28 days under ideal warm temperatures.
The cycle begins when a female weevil lays small, white, oval-shaped eggs. Many species bore a hole directly into a plant stem, seed, or grain to deposit their eggs, sometimes sealing the hole afterward. A female can lay many eggs, which typically hatch in about 3 to 14 days.
Once hatched, the weevil enters its larval stage, appearing as a white to yellow, worm-like grub. Weevil larvae are legless and often have a curved or C-shaped body. This is the primary feeding stage, where larvae consume their host plant’s roots or feed internally on seeds and grains. The larval stage can last for several weeks to up to two months, sometimes even longer depending on the species and conditions.
After sufficient feeding and growth, the larva transforms into a pupa. During this inactive stage, the weevil is encased, often within the grain or plant material it fed upon. Significant physiological changes occur as the weevil reorganizes its body into the adult form. This pupal stage can last approximately three weeks, though it varies by species and temperature.
Finally, the adult weevil emerges from the pupal stage. Most adult weevils are small, typically less than a quarter of an inch long, and possess a hard exoskeleton, six legs, and a distinctive snout-like mouthpiece called a rostrum. The adult stage is primarily for reproduction, with most adults living for about two to five months, continuing to feed and lay eggs.
Identifying Weevil Life Stages
Identifying weevil life stages often requires careful observation due to their small size and hidden habits. Weevil eggs are minute, small, white, and oval, making them difficult to spot without magnification.
Weevil larvae are more recognizable. They are typically soft-bodied, white to creamy white, and distinctly legless, often appearing as small grubs. Some species, like the vine weevil, have a characteristic C-shape. They can grow up to 1.5 cm for some species.
Pupae are generally white or creamy white and are encased. Unlike the legless larvae, developing adult features, such as legs and antennae, can sometimes be seen folded beneath the body. They may show slight movement if disturbed.
Adult weevils are the most easily identifiable stage. They typically range from 1/13 to 1/4 inch in length, with colors varying from reddish-brown to black. Many have elbowed antennae that attach to their snout. Some species, like the rice weevil, have four light-colored spots on their wing covers and can fly, while others, like the granary weevil, are flightless.
Where Weevils Are Found
Weevils are found in a wide range of environments, adapting their habitats to their specific food sources. Many species are considered agricultural pests, infesting crops in fields and gardens, including fruits, nuts, cotton, and various plants. Root weevils, for instance, feed on plant roots and can damage garden plants.
Weevils are commonly encountered as pantry pests. They infest items such as grains (rice, wheat, corn), flour, pasta, beans, cereals, and birdseed. Their presence can be indicated by small holes in kernels or fine dust in containers.
Weevils typically seek out warm, moist conditions and can enter homes through cracks and openings in search of food or shelter. Infestations often begin with weevils entering food products at the point of purchase or storage.