1. Grain pests:
Granary, rice and corn weevils only develop inside large starchy seeds or equivalent products, for example, macaroni, noodles or hard-pressed flour. The man-made storages with lots of large starchy seeds (wheat, rye, barley, oats, rice, corn, etc.) have become their main habitat. The larvae of most other grain pests eat of the kernels from the outside. Some species have so weak mouth parts that they must either nibble of the soft seeds before reaching the endosperm, or infest grain that for some reason has been damaged. These so-called secondary grain pests typically include species such as saw-toothed grain beetles, rust-red grain beetles, mealworm beetles, dark flour beetles and rice weevils as well as the larvae of brown house moths, Mediterranean flour moths and certain other moths. To them, flour, grains, baked goods and kernel damaged by granary weevils are just variations on the theme “damaged seeds.” The natural niches of these secondary grain pests are probably birds’ nests, where they feed on the spilled feed, when the birds feed their young.
2. Leguminous plant pests:
Seeds of the pea family (peas, beans, lentils etc.) are infested mainly by the specialist species, bean weevils, which in warmer countries lay their eggs in the seeds while the plants are still growing. Imported seeds containing these weevils may be massively damaged during storage. Insects in similar products, such as coffee bean weevils can infest leguminous plants too. Bean flour and pea flour are somewhat toxic to flour moths.
3. Pests of nut kernels and dried fruits:
The moths dominate this area. It is essentially the same species of moth that eat almonds, peanuts, hazelnuts and other nuts, which in storage are freed of the hard shell, and the dried fruit (raisins, prunes, dates, figs, apricots, etc.). Also cocoa beans are infested by the same moths. Chocolate, marzipan and praline goods are almost exclusively infested by moth larvae. The adult moths smell their way to the goods and lay their eggs directly in the raw materials or finished products. To moths chocolate and marzipan are merely substitutes for real nuts which they prefer. Few beetles infest nuts and dry fruit. It is usually be the same beetles that are secondary grain pests or seed-eaters in bird nests. Merchant grain beetles prefer nut kernels over cereal products whenever it is possible to choose, and that is perhaps its natural niche in bird nests. Its mouth is so weak that it cannot bite through peanuts capsules.