* Adults are good fliers and easily disperse. Adults chew into the grain kernels from the
outside and also to lay eggs. Females can lay 300 to 400 eggs typically one per cavity.
Larvae develop through several stages (instars) inside the grain kernels and also pupate
inside the kernel. They may complete a generation in a month in warm conditions. Adults
often live for 7 to 8 months and some records are over 2 years.
* The egg, larva, and pupa stages of both weevils occur in the grain kernels and are
rarely seen. Feeding is done within the grain kernel, and adults cut exit holes to emerge.
Emergence holes of the granary weevil are larger than those of the rice weevil, and tend to
be more ragged than smooth and round. Females drill a tiny hole in the grain kernel; deposit
an egg in the cavity, then plug the hole with a gelatinous secretion. The egg hatches into
a young larva which bores toward the centre of the kkernel, feeds, grows, and pupates
there. New adults bore emergence holes from the inside, then leave to mate and begin a
new generation.
* Female granary weevils lay from 36 to 254 eggs. At 80 to 86 degrees F, 75- to
90-percent relative humidity, eggs hatch in wheat with a moisture content of 13.5 to 19.6
percent in 3 days. Larvae mature in 18 days, and the pupa in 6 days. The life cycle is about
30 to 40 days during the summer, and 123 to 148 days during the winter, depending on
temperature. Adults live 7 to 8 months. Female rice weevils lay between 300 to 400 eggs,
with the life cycle requiring about 32 days for completion. Rice weevil adults live 3 to 6
months, infesting grain in the field, especially in the South. Two larvae can develop in one
wheat kernel, but only one larva of the granary weevil can develop per wheat kernel. Both
granary and rice weevils feign death by drawing up their legs close to the body, falling, and
remaining silent when disturbed.