This section is from the book "Commercial Gardening Vol3", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
Cob, filbert, and wild hazels are often badly damaged by a maggot or grub which eats out the kernel. This is the larva of the Nut Weevil (Balaninus nucum). This weevil can readily be distinguished by its long curved proboscis. In length it is about 1/3 in., the colour tawny brown, densely clothed with golden-brown pubescence. The beetles lay their eggs in the small and tender nuts, first piercing them with their proboscis. The egg hatches in eight or ten days. The maggot, which feeds on the kernel, is white, footless, and fleshy, fat and curved, with brown head; length rather more than 1/3 in. When mature the maggot eats its way out of the nut and leaves behind a small round hole in the shell. The winter is passed in the pupal stage in a cocoon of earth in the soil.