Tenebroides mauritanicus (Linnaeus, 1758)

A cosmopolitan species, originally from Africa, and in some regions a significant pest of stored products.  They occur especially in grain silos, granaries, warehouses and other commercial sites but also in houses where both adults and larvae feed on a wide variety of foodstuffs; cereals, processed breakfast products, potatoes, nuts and fruit etc, the adults are opportunistic and will often lay eggs under flaps of cartons or among packaging within storage boxes. The species occurs only occasionally in the U.K. but is never a pest. Adults and larvae can chew through sacking, card and wood so allowing other pest species access to products, and unlike other grain pests they feed on both whole grain and flour. They are also predatory and actively hunt and feed on other pest species e.g. Oryzaephilus spp. Both stages are notorious for being able to burrow into wooden structures and remain dormant for long periods if food is unavailable, and these burrows are also used by other insects. They can also be a serious pest of stored tobacco; here both stages bore through bales in search of prey, consuming the product as they go. These habits may be an adaptation of their natural lifestyle; in Europe the genus occurs in the wild (although such specimens are often thought to be a subspecies of the present species or even conspecific), living under bark and predating other wood boring insects. Females lay eggs in groups of about 50 loosely among stored products which hatch, depending on temperature, in around 10 days and each female will lay around 1000 eggs. Larval development depends upon the type of food, e.g. on tobacco they may take 2 or 3 years, and temperature; in unfavourable conditions they can go without food for prolonged periods, more than 50 days for adults and more than 120 days for the larvae. In general the larvae consume only the soft parts of grains such as wheat and oats and so may destroy large amounts of material; a single larva has recorded destroying a hundred thousand grains. The larvae grow to 20mm and so are among the largest to be found among stored grains; they are greyish white with a dark head and pronotal plates. The dorsal surface of the terminal abdominal segment is dark with two robust upturned urogomphi. They migrate away from the food source to pupate and pupal chambers have been found in some unusual places e.g. in books, within corks inserted in bottles and inside a bottle of milk. Adults eclose between 1 and 3 weeks after pupation. In temperate regions there may be 2 generations a year with a partial third, in tropical regions there are three.