Insects found in boxes of pasta, rice and other household pantry products are often already present when the food item is purchased. The most common grain-eaters are weevils, meal moths and beetles.
Pantry pests that infiltrate households often go unnoticed until the insects are large enough to be seen easily or until their numbers become so great that their activity is unmistakable. While it is possible for the bugs to enter the home from the outside and then multiply, more often their presence in boxes or bags of food originated at a processing plant, storage warehouse, retail store or even the delivery truck.
If insects such as beetles or moths are introduced into the home during their egg, larva or pupa stages, they will likely go undetected until they are adults. Once the bugs are spotted, all possibly affected foods should be discarded and areas of infestation thoroughly vacuumed and washed.