Insect identification > Coleoptera > Rhynchophora > Alfalfa weevil

Alfalfa weevil


The alfalfa weevil (Hypera postica Gyll.). - This European beetle was found in Utah in 1904 and has spread into parts of Montana, Idaho, Wyoming, Colorado, Nevada, California and Oregon.

The adult is a snout beetle only about 3/16 inch long, brown when fresh but almost black after a time. It winters as the adult close to the ground or in crevices there, and in some cases under rubbish, and in severe winters many are killed by the cold. In the spring the weevils become active and fly, often many miles, in search of food.

They puncture the stems of the alfalfa plants and sometimes lay as many as 40 eggs in a puncture and an average of perhaps 700 eggs in all.

The eggs hatch in about 10 days and the larvae feed at first on the leaf buds, stopping the growth of the plant, and later on the leaves and, when many are present, stripping the plants. After feeding about 2 months they drop to the ground and spin a loose, silken network cocoon in which they remain about 10 days before emerging as adults.

Late in summer these adults make a flight, looking for places in which to winter, and may go quite long distances. There is only one generation a year.